Characteristics of infections with ancestral, Beta and Delta variants of SARS-CoV-2 in the PHIRST-C community cohort study, South Africa, 2020-2021.

BACKGROUND: Data on the characteristics of individuals with mild and asymptomatic infections with different SARS-CoV-2 variants are limited. We therefore compared the characteristics of individuals infected with ancestral, Beta and Delta SARS-CoV-2 variants in South Africa. METHODS: We conducted a prospective cohort study in a rural and an urban site during July 2020-August 2021. Mid-turbinate nasal swabs were collected twice-weekly from household members irrespective of symptoms and tested for SARS-CoV-2 using real-time reverse transcription polymerase chain reaction (rRT-PCR). Differences in demographic and clinical characteristics, shedding and cycle threshold (Ct) value of infection episodes by variant were evaluated using multinomial regression. Overall and age-specific incidence rates of infection were compared by variant. RESULTS: We included 1200 individuals from 222 households and 648 rRT-PCR-confirmed infection episodes (66, 10% ancestral, 260, 40% Beta, 322, 50% Delta). Symptomatic proportion was similar for ancestral (7, 11%), Beta (44, 17%), and Delta (46, 14%) infections (p=0.4). After accounting for previous infection, peak incidence shifted to younger age groups in successive waves (40-59 years ancestral, 19-39 years Beta, 13-18 years Delta). On multivariable analysis, compared to ancestral, Beta infection was more common in individuals aged 5-12 years (vs 19-39)(adjusted odds ratio (aOR) 2.6, 95% confidence interval (CI)1.1-6.6) and PCR cycle threshold (Ct) value <30 (vs >35)(aOR 3.2, 95%CI 1.3-7.9), while Delta was more common in individuals aged <5 (aOR 6.7, 95%CI1.4-31.2) and 5-12 years (aOR 6.6 95%CI2.6-16.7)(vs 19-39) and Ct value <30 (aOR 4.5, 95%CI 1.3-15.5) and 30-35 (aOR 6.0, 95%CI 2.3-15.7)(vs >35). CONCLUSIONS: Consecutive SARS-CoV-2 waves with Beta and Delta variants were associated with a shift to younger individuals. Beta and Delta infections were associated with higher peak viral loads, potentially increasing infectiousness.

An external quality assessment feasibility study; cross laboratory comparison of haemagglutination inhibition assay and microneutralization assay performance for seasonal influenza serology testing: A FLUCOP study.

Introduction: External Quality Assessment (EQA) schemes are designed to provide a snapshot of laboratory proficiency, identifying issues and providing feedback to improve laboratory performance and inter-laboratory agreement in testing. Currently there are no international EQA schemes for seasonal influenza serology testing. Here we present a feasibility study for conducting an EQA scheme for influenza serology methods. Methods: We invited participant laboratories from industry, contract research organizations (CROs), academia and public health institutions who regularly conduct hemagglutination inhibition (HAI) and microneutralization (MN) assays and have an interest in serology standardization. In total 16 laboratories returned data including 19 data sets for HAI assays and 9 data sets for MN assays. Results: Within run analysis demonstrated good laboratory performance for HAI, with intrinsically higher levels of intra-assay variation for MN assays. Between run analysis showed laboratory and strain specific issues, particularly with B strains for HAI, whilst MN testing was consistently good across labs and strains. Inter-laboratory variability was higher for MN assays than HAI, however both assays showed a significant reduction in inter-laboratory variation when a human sera pool is used as a standard for normalization. Discussion: This study has received positive feedback from participants, highlighting the benefit such an EQA scheme would have on improving laboratory performance, reducing inter laboratory variation and raising awareness of both harmonized protocol use and the benefit of biological standards for seasonal influenza serology testing.

Household Transmission of Severe Acute Respiratory Syndrome Coronavirus 2 From Adult Index Cases With and Without Human Immunodeficiency Virus in South Africa, 2020-2021: A Case-Ascertained, Prospective, Observational Household Transmission Study.

BACKGROUND: In South Africa, 19% of adults are living with human immunodeficiency virus (HIV; LWH). Few data on the influence of HIV on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) household transmission are available. METHODS: We performed a case-ascertained, prospective household transmission study of symptomatic adult index SARS-CoV-2 cases LWH and not living with HIV (NLWH) and their contacts from October 2020 to September 2021. Households were followed up 3 times a week for 6 weeks to collect nasal swabs for SARS-CoV-2 testing. We estimated household cumulative infection risk (HCIR) and duration of SARS-CoV-2 positivity (at a cycle threshold value <30 as proxy for high viral load). RESULTS: HCIR was 59% (220 of 373), not differing by index HIV status (60% LWH vs 58% NLWH). HCIR increased with index case age (35-59 years: adjusted OR [aOR], 3.4; 95% CI, 1.5-7.8 and ≥60 years: aOR, 3.1; 95% CI, 1.0-10.1) compared with 18-34 years and with contacts' age, 13-17 years (aOR, 7.1; 95% CI, 1.5-33.9) and 18-34 years (aOR, 4.4; 95% CI, 1.0-18.4) compared with <5 years. Mean positivity was longer in cases LWH (adjusted hazard ratio, 0.4; 95% CI, .1-.9). CONCLUSIONS: Index HIV status was not associated with higher HCIR, but cases LWH had longer positivity duration. Adults aged >35 years were more likely to transmit and individuals aged 13-34 to be infected SARS-CoV-2 in the household. As HIV infection may increase transmission, health services must maintain HIV testing and antiretroviral therapy initiation.

Risk Factors for Severe Coronavirus Disease 2019 Among Human Immunodeficiency Virus-Infected and -Uninfected Individuals in South Africa, April 2020-March 2022: Data From Sentinel Surveillance.

Background: Data on risk factors for coronavirus disease 2019 (COVID-19)-associated hospitalization and mortality in high human immunodeficiency virus (HIV) prevalence settings are limited. Methods: Using existing syndromic surveillance programs for influenza-like-illness and severe respiratory illness at sentinel sites in South Africa, we identified factors associated with COVID-19 hospitalization and mortality. Results: From April 2020 through March 2022, severe acute respiratory syndrome coronavirus 2 was detected in 24.0% (660 of 2746) of outpatient and 32.5% (2282 of 7025) of inpatient cases. Factors associated with COVID-19-associated hospitalization included the following: older age (25-44 [adjusted odds ratio {aOR}= 1.8, 95% confidence interval (CI) = 1.1-2.9], 45-64 [aOR = 6.8, 95% CI = 4.2-11.0] and ≥65 years [aOR = 26.6, 95% CI = 14.4-49.1] vs 15-24 years); black race (aOR, 3.3; 95% CI, 2.2-5.0); obesity (aOR, 2.3; 95% CI, 1.4-3.9); asthma (aOR, 3.5; 95% CI, 1.4-8.9); diabetes mellitus (aOR, 5.3; 95% CI, 3.1-9.3); HIV with CD4 ≥200/mm3 (aOR, 1.5; 95% CI, 1.1-2.2) and CD4 <200/mm3 (aOR, 10.5; 95% CI, 5.1-21.6) or tuberculosis (aOR, 12.8; 95% CI, 2.8-58.5). Infection with Beta (aOR, 0.5; 95% CI, .3-.7) vs Delta variant and being fully vaccinated (aOR, 0.1; 95% CI, .1-.3) were less associated with COVID-19 hospitalization. In-hospital mortality was increased in older age (45-64 years [aOR, 2.2; 95% CI, 1.6-3.2] and ≥65 years [aOR, 4.0; 95% CI, 2.8-5.8] vs 25-44 years) and male sex (aOR, 1.3; 95% CI, 1.0-1.6) and was lower in Omicron-infected (aOR, 0.3; 95% CI, .2-.6) vs Delta-infected individuals. Conclusions: Active syndromic surveillance encompassing clinical, laboratory, and genomic data identified setting-specific risk factors associated with COVID-19 severity that will inform prioritization of COVID-19 vaccine distribution. Elderly people with tuberculosis or people with HIV, especially severely immunosuppressed, should be prioritized for vaccination.

SARS-CoV-2 transmission, persistence of immunity, and estimates of Omicron's impact in South African population cohorts.

Understanding the build-up of immunity with successive severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants and the epidemiological conditions that favor rapidly expanding epidemics will help facilitate future pandemic control. We analyzed high-resolution infection and serology data from two longitudinal household cohorts in South Africa to reveal high cumulative infection rates and durable cross-protective immunity conferred by prior infection in the pre-Omicron era. Building on the history of past exposures to different SARS-CoV-2 variants and vaccination in the cohort most representative of South Africa's high urbanization rate, we used mathematical models to explore the fitness advantage of the Omicron variant and its epidemic trajectory. Modeling suggests that the Omicron wave likely infected a large fraction (44 to 81%) of the population, leaving a complex landscape of population immunity primed and boosted with antigenically distinct variants. We project that future SARS-CoV-2 resurgences are likely under a range of scenarios of viral characteristics, population contacts, and residual cross-protection.

Seroprevalence of Severe Acute Respiratory Syndrome Coronavirus 2 After the Second Wave in South Africa in Human Immunodeficiency Virus-Infected and Uninfected Persons: A Cross-Sectional Household Survey.

BACKGROUND: Seroprevalence studies are important for quantifying the burden of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in resource-constrained countries. METHODS: We conducted a cross-sectional household survey spanning the second pandemic wave (November 2020 to April 2021) in 3 communities. Blood was collected for SARS-CoV-2 antibody (2 enzyme-linked immunosorbent assays targeting spike and nucleocapsid) and human immunodeficiency virus (HIV) testing. An individual was considered seropositive if testing positive on ≥1 assay. Factors associated with infection, and the age-standardized infection case detection rate, infection hospitalization rate, and infection fatality rate were calculated. RESULTS: Overall, 7959 participants were enrolled, with a median age of 34 years and an HIV prevalence of 22.7%. SARS-CoV-2 seroprevalence was 45.2% (95% confidence interval 43.7%-46.7%) and increased from 26.9% among individuals enrolled in December 2020 to 47.1% among those enrolled in April 2021. On multivariable analysis, seropositivity was associated with age, sex, race, being overweight/obese, having respiratory symptoms, and low socioeconomic status. Persons living with HIV with high viral load were less likely to be seropositive than HIV-uninfected individuals. The site-specific infection case detection rate, infection hospitalization rate, and infection fatality rate ranged across sites from 4.4% to 8.2%, 1.2% to 2.5%, and 0.3% to 0.6%, respectively. CONCLUSIONS: South Africa has experienced a large burden of SARS-CoV-2 infections, with <10% of infections diagnosed. Lower seroprevalence among persons living with HIV who are not virally suppressed, likely as a result of inadequate antibody production, highlights the need to prioritize this group for intervention.

SARS-CoV-2 Seroprevalence after Third Wave of Infections, South Africa.

By November 2021, after the third wave of severe acute respiratory syndrome coronavirus 2 infections in South Africa, seroprevalence was 60% in a rural community and 70% in an urban community. High seroprevalence before the Omicron variant emerged may have contributed to reduced illness severity observed in the fourth wave.

SARS-CoV-2 incidence, transmission, and reinfection in a rural and an urban setting: results of the PHIRST-C cohort study, South Africa, 2020-21.

BACKGROUND: By August, 2021, South Africa had been affected by three waves of SARS-CoV-2; the second associated with the beta variant and the third with the delta variant. Data on SARS-CoV-2 burden, transmission, and asymptomatic infections from Africa are scarce. We aimed to evaluate SARS-CoV-2 burden and transmission in one rural and one urban community in South Africa. METHODS: We conducted a prospective cohort study of households in Agincourt, Mpumalanga province (rural site) and Klerksdorp, North West province (urban site) from July, 2020 to August, 2021. We randomly selected households for the rural site from a health and sociodemographic surveillance system and for the urban site using GPS coordinates. Households with more than two members and where at least 75% of members consented to participate were eligible. Midturbinate nasal swabs were collected twice a week from household members irrespective of symptoms and tested for SARS-CoV-2 using real-time RT-PCR (RT-rtPCR). Serum was collected every 2 months and tested for anti-SARS-CoV-2 antibodies. Main outcomes were the cumulative incidence of SARS-CoV-2 infection, frequency of reinfection, symptomatic fraction (percent of infected individuals with ≥1 symptom), the duration of viral RNA shedding (number of days of SARS-CoV-2 RT-rtPCR positivity), and the household cumulative infection risk (HCIR; number of infected household contacts divided by the number of susceptible household members). FINDINGS: 222 households (114 at the rural site and 108 at the urban site), and 1200 household members (643 at the rural site and 557 at the urban site) were included in the analysis. For 115 759 nasal specimens from 1200 household members (follow-up 92·5%), 1976 (1·7%) were SARS-CoV-2-positive on RT-rtPCR. By RT-rtPCR and serology combined, 749 of 1200 individuals (62·4% [95% CI 58·1-66·4]) had at least one SARS-CoV-2 infection episode, and 87 of 749 (11·6% [9·4-14·2]) were reinfected. The mean infection episode duration was 11·6 days (SD 9·0; range 4-137). Of 662 RT-rtPCR-confirmed episodes (>14 days after the start of follow-up) with available data, 97 (14·7% [11·9-17·9]) were symptomatic with at least one symptom (in individuals aged <19 years, 28 [7·5%] of 373 episodes symptomatic; in individuals aged ≥19 years, 69 [23·9%] of 289 episodes symptomatic). Among 222 households, 200 (90·1% [85·3-93·7]) had at least one SARS-CoV-2-positive individual on RT-rtPCR or serology. HCIR overall was 23·9% (195 of 817 susceptible household members infected [95% CI 19·8-28·4]). HCIR was 23·3% (20 of 86) for symptomatic index cases and 23·9% (175 of 731) for asymptomatic index cases (univariate odds ratio [OR] 1·0 [95% CI 0·5-2·0]). On multivariable analysis, accounting for age and sex, low minimum cycle threshold value (≤30 vs >30) of the index case (OR 5·3 [2·3-12·4]) and beta and delta variant infection (vs Wuhan-Hu-1, OR 3·3 [1·4-8·2] and 10·4 [4·1-26·7], respectively) were associated with increased HCIR. People living with HIV who were not virally supressed (≥400 viral load copies per mL) were more likely to develop symptomatic illness when infected with SAR-CoV-2 (OR 3·3 [1·3-8·4]), and shed SARS-CoV-2 for longer (hazard ratio 0·4 [95% CI 0·3-0·6]) compared with HIV-uninfected individuals. INTERPRETATION: In this study, 565 (85·3%) SARS-CoV-2 infections were asymptomatic and index case symptom status did not affect HCIR, suggesting a limited role for control measures targeting symptomatic individuals. Increased household transmission of beta and delta variants was likely to have contributed to successive waves of SARS-CoV-2 infection, with more than 60% of individuals infected by the end of follow-up. FUNDING: US CDC, South Africa National Institute for Communicable Diseases, and Wellcome Trust.

Prolonged Shedding of Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) at High Viral Loads Among Hospitalized Immunocompromised Persons Living With Human Immunodeficiency Virus (HIV), South Africa.

BACKGROUND: We assessed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA shedding duration and magnitude among persons living with human immunodeficiency virus (HIV, PLHIV). METHODS: From May through December 2020, we conducted a prospective cohort study at 20 hospitals in South Africa. Adults hospitalized with symptomatic coronavirus disease 2019 (COVID-19) were enrolled and followed every 2 days with nasopharyngeal/oropharyngeal (NP/OP) swabs until documentation of cessation of SARS-CoV-2 shedding (2 consecutive negative NP/OP swabs). Real-time reverse transcription-polymerase chain reaction testing for SARS-CoV-2 was performed, and cycle-threshold (Ct) values < 30 were considered a proxy for high SARS-CoV-2 viral load. Factors associated with prolonged shedding were assessed using accelerated time-failure Weibull regression models. RESULTS: Of 2175 COVID-19 patients screened, 300 were enrolled, and 257 individuals (155 HIV-uninfected and 102 PLHIV) had > 1 swabbing visit (median 5 visits [range 2-21]). Median time to cessation of shedding was 13 days (interquartile range [IQR] 6-25) and did not differ significantly by HIV infection. Among a subset of 94 patients (41 PLHIV and 53 HIV-uninfected) with initial respiratory sample Ct-value < 30, median time of shedding at high SARS-CoV-2 viral load was 8 days (IQR 4-17). This was significantly longer in PLHIV with CD4 count < 200 cells/µL, compared to HIV-uninfected persons (median 27 days [IQR 8-43] vs 7 days [IQR 4-13]; adjusted hazard ratio [aHR] 0.14, 95% confidence interval [CI] .07-.28, P < .001), as well as in unsuppressed-HIV versus HIV-uninfected persons. CONCLUSIONS: Although SARS-CoV-2 shedding duration did not differ significantly by HIV infection, among a subset with high initial SARS-CoV-2 viral loads, immunocompromised PLHIV shed SARS-CoV-2 at high viral loads for longer than HIV-uninfected persons. Better HIV control may potentially decrease transmission time of SARS-CoV-2.

SARS-CoV-2 incidence, transmission and reinfection in a rural and an urban setting: results of the PHIRST-C cohort study, South Africa, 2020-2021.

BACKGROUND: By August 2021, South Africa experienced three SARS-CoV-2 waves; the second and third associated with emergence of Beta and Delta variants respectively. METHODS: We conducted a prospective cohort study during July 2020-August 2021 in one rural and one urban community. Mid-turbinate nasal swabs were collected twice-weekly from household members irrespective of symptoms and tested for SARS-CoV-2 using real-time reverse transcription polymerase chain reaction (rRT-PCR). Serum was collected every two months and tested for anti-SARS-CoV-2 antibodies. RESULTS: Among 115,759 nasal specimens from 1,200 members (follow-up rate 93%), 1976 (2%) were SARS-CoV-2-positive. By rRT-PCR and serology combined, 62% (749/1200) of individuals experienced ≥1 SARS-CoV-2 infection episode, and 12% (87/749) experienced reinfection. Of 662 PCR-confirmed episodes with available data, 15% (n=97) were associated with ≥1 symptom. Among 222 households, 200 (90%) had ≥1 SARS-CoV-2-positive individual. Household cumulative infection risk (HCIR) was 25% (213/856). On multivariable analysis, accounting for age and sex, index case lower cycle threshold value (OR 3.9, 95%CI 1.7-8.8), urban community (OR 2.0,95%CI 1.1-3.9), Beta (OR 4.2, 95%CI 1.7-10.1) and Delta (OR 14.6, 95%CI 5.7-37.5) variant infection were associated with increased HCIR. HCIR was similar for symptomatic (21/110, 19%) and asymptomatic (195/775, 25%) index cases (p=0.165). Attack rates were highest in individuals aged 13-18 years and individuals in this age group were more likely to experience repeat infections and to acquire SARS-CoV-2 infection. People living with HIV who were not virally supressed were more likely to develop symptomatic illness, and shed SARS-CoV-2 for longer compared to HIV-uninfected individuals. CONCLUSIONS: In this study, 85% of SARS-CoV-2 infections were asymptomatic and index case symptom status did not affect HCIR, suggesting a limited role for control measures targeting symptomatic individuals. Increased household transmission of Beta and Delta variants, likely contributed to successive waves, with >60% of individuals infected by the end of follow-up. RESEARCH IN CONTEXT: Evidence before this study: Previous studies have generated wide-ranging estimates of the proportion of SARS-CoV-2 infections which are asymptomatic. A recent systematic review found that 20% (95% CI 3%-67%) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections remained asymptomatic throughout infection and that transmission from asymptomatic individuals was reduced. A systematic review and meta-analysis of 87 household transmission studies of SARS-CoV-2 found an estimated secondary attack rate of 19% (95% CI 16-22). The review also found that household secondary attack rates were increased from symptomatic index cases and that adults were more likely to acquire infection. As of December 2021, South Africa experienced three waves of SARS-CoV-2 infections; the second and third waves were associated with circulation of Beta and Delta variants respectively. SARS-CoV-2 vaccines became available in February 2021, but uptake was low in study sites reaching 5% fully vaccinated at the end of follow up. Studies to quantify the burden of asymptomatic infections, symptomatic fraction, reinfection frequency, duration of shedding and household transmission of SARS-CoV-2 from asymptomatically infected individuals have mostly been conducted as part of outbreak investigations or in specific settings. Comprehensive systematic community studies of SARS-CoV-2 burden and transmission including for the Beta and Delta variants are lacking, especially in low vaccination settings.Added value of this study: We conducted a unique detailed COVID-19 household cohort study over a 13 month period in South Africa, with real time reverse transcriptase polymerase chain reaction (rRT-PCR) testing twice a week irrespective of symptoms and bimonthly serology. By the end of the study in August 2021, 749 (62%) of 1200 individuals from 222 randomly sampled households in a rural and an urban community in South Africa had at least one confirmed SARS-CoV-2 infection, detected on rRT-PCR and/or serology, and 12% (87/749) experienced reinfection. Symptom data were analysed for 662 rRT-PCR-confirmed infection episodes that occurred >14 days after the start of follow-up (of a total of 718 rRT-PCR-confirmed episodes), of these, 15% (n=97) were associated with one or more symptoms. Among symptomatic indvidiausl, 9% (n=9) were hospitalised and 2% (n=2) died. Ninety percent (200/222) of included households, had one or more individual infected with SARS-CoV-2 on rRT-PCR and/or serology within the household. SARS-CoV-2 infected index cases transmitted the infection to 25% (213/856) of susceptible household contacts. Index case ribonucleic acid (RNA) viral load proxied by rRT-PCR cycle threshold value was strongly predictive of household transmission. Presence of symptoms in the index case was not associated with household transmission. Household transmission was four times greater from index cases infected with Beta variant and fifteen times greater from index cases infected with Delta variant compared to wild-type infection. Attack rates were highest in individuals aged 13-18 years and individuals in this age group were more likely to experience repeat infections and to acquire SARS-CoV-2 infection within households. People living with HIV (PLHIV) who were not virally supressed were more likely to develop symptomatic illness when infected with SARS-CoV-2, and shed SARS-CoV-2 for longer when compared to HIV-uninfected individuals.Implications of all the available evidence: We found a high rate of SARS-CoV-2 infection in households in a rural community and an urban community in South Africa, with the majority of infections being asymptomatic in individuals of all ages. Asymptomatic individuals transmitted SARS-CoV-2 at similar levels to symptomatic individuals suggesting that interventions targeting symptomatic individuals such as symptom-based testing and contact tracing of individuals tested because they report symptoms may have a limited impact as control measures. Increased household transmission of Beta and Delta variants, likely contributed to recurrent waves of COVID-19, with >60% of individuals infected by the end of follow-up. Higher attack rates, reinfection and acquisition in adolescents and prolonged SARS-CoV-2 shedding in PLHIV who were not virally suppressed suggests that prioritised vaccination of individuals in these groups could impact community transmission.

SARS-CoV-2 Seroprevalence in a Rural and Urban Household Cohort during First and Second Waves of Infections, South Africa, July 2020-March 2021.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections may be underestimated because of limited access to testing. We measured SARS-CoV-2 seroprevalence in South Africa every 2 months during July 2020-March 2021 in randomly selected household cohorts in 2 communities. We compared seroprevalence to reported laboratory-confirmed infections, hospitalizations, and deaths to calculate infection-case, infection-hospitalization, and infection-fatality ratios in 2 waves of infection. Post-second wave seroprevalence ranged from 18% in the rural community children <5 years of age, to 59% in urban community adults 35-59 years of age. The second wave saw a shift in age distribution of case-patients in the urban community (from persons 35-59 years of age to persons at the extremes of age), higher attack rates in the rural community, and a higher infection-fatality ratio in the urban community. Approximately 95% of SARS-CoV-2 infections were not reported to national surveillance.

Cohort profile: A Prospective Household cohort study of Influenza, Respiratory syncytial virus and other respiratory pathogens community burden and Transmission dynamics in South Africa, 2016-2018.

PURPOSE: The PHIRST study (Prospective Household cohort study of Influenza, Respiratory Syncytial virus, and other respiratory pathogens community burden and Transmission dynamics in South Africa) aimed to estimate the community burden of influenza and respiratory syncytial virus (RSV) including the incidence of infection, symptomatic fraction, and to assess household transmission. PARTICIPANTS: We enrolled 1684 individuals in 327 randomly selected households in a rural and an urban site over three consecutive influenza and two RSV seasons. A new cohort of households was enrolled each year. Participants were sampled with nasopharyngeal swabs twice-weekly during the RSV and influenza seasons of the year of enrolment. Serology samples were collected at enrolment and before and after the influenza season annually. FINDINGS TO DATE: There were 122 113 potential individual follow-up visits over the 3 years, and participants were interviewed for 105 783 (87%) of these. Out of 105 683 nasopharyngeal swabs, 1258 (1%) and 1026 (1%) tested positive on polymerase chain reaction (PCR) for influenza viruses and RSV, respectively. Over one third of individuals had PCR-confirmed influenza each year. Overall, there was influenza transmission to 10% of household contacts of an index case. FUTURE PLANS: Future planned analyses include analysis of influenza serology results and RSV burden and transmission. Households enrolled in the PHIRST study during 2016-2018 were eligible for inclusion in a study of SARS-CoV-2 transmission initiated in July 2020. This study uses similar testing frequency to assess the community burden of SARS-CoV-2 infection and the role of asymptomatic infection in virus transmission.

Impact of Maternal HIV Infection and Placental Malaria on the Transplacental Transfer of Influenza Antibodies in Mother-Infant Pairs in Malawi, 2013-2014.

BACKGROUND: Maternal influenza vaccination protects infants against influenza virus infection. Impaired transplacental transfer of influenza antibodies may reduce this protection. METHODS: We conducted a cross-sectional study of influenza vaccine-naïve pregnant women recruited at delivery from Blantyre (urban, low malaria transmission) and Chikwawa (rural, high malaria transmission) in Southern Malawi. HIV-infected mothers were excluded in Chikwawa. Maternal and cord blood antibodies against circulating influenza strains A/California/7/2009, A/Victoria/361/2011, B/Brisbane/60/2008, and B/Wisconsin/1/2010 were measured by hemagglutination inhibition (HAI). We studied the impact of maternal HIV infection and placental malaria on influenza antibody levels in mother-infant pairs in Blantyre and Chikwawa, respectively. RESULTS: We included 454 mother-infant pairs (Blantyre, n = 253; Chikwawa, n = 201). HIV-infected mothers and their infants had lower seropositivity (HAI titer ≥1:40) against influenza A(H1N1)pdm09 (mothers, 24.3 vs 45.4%; P = .02; infants, 24.3 vs 50.5%; P = .003) and A(H3N2) (mothers, 37.8% vs 63.9%; P = .003; infants, 43.2 vs 64.8%; P = .01), whereas placental malaria had an inconsistent effect on maternal and infant seropositivity. In multivariable analyses, maternal HIV infection was associated with reduced infant seropositivity (A(H1N1)pdm09: adjusted odds ratio [aOR], 0.34; 95% confidence interval [CI], 0.15-0.79; A(H3N2): aOR, 0.43; 95% CI, 0.21-0.89). Transplacental transfer was not impaired by maternal HIV or placental malaria. CONCLUSIONS: Maternal HIV infection influenced maternal antibody response to influenza A virus infection, and thereby antibody levels in newborns, but did not affect transplacental antibody transfer.

Sequencing and analysis of globally obtained human parainfluenza viruses 1 and 3 genomes.

Human Parainfluenza viruses (HPIV) type 1 and 3 are important causes of respiratory tract infections in young children globally. HPIV infections do not confer complete protective immunity so reinfections occur throughout life. Since no effective vaccine is available for the two virus subtypes, comprehensive understanding of HPIV-1 and HPIV-3 genetic and epidemic features is important for diagnosis, prevention, and treatment of HPIV-1 and HPIV-3 infections. Relatively few whole genome sequences are available for both HPIV-1 and HPIV-3 viruses, so our study sought to provide whole genome sequences from multiple countries to further the understanding of the global diversity of HPIV at a whole-genome level. We collected HPIV-1 and HPIV-3 samples and isolates from Argentina, Australia, France, Mexico, South Africa, Switzerland, and USA from the years 2003-2011 and sequenced the genomes of 40 HPIV-1 and 75 HPIV-3 viruses with Sanger and next-generation sequencing with the Ion Torrent, Illumina, and 454 platforms. Phylogenetic analysis showed that the HPIV-1 genome is evolving at an estimated rate of 4.97 × 10-4 mutations/site/year (95% highest posterior density 4.55 × 10-4 to 5.38 × 10-4) and the HPIV-3 genome is evolving at a similar rate (3.59 × 10-4 mutations/site/year, 95% highest posterior density 3.26 × 10-4 to 3.94 × 10-4). There were multiple genetically distinct lineages of both HPIV-1 and 3 circulating on a global scale. Further surveillance and whole-genome sequencing are greatly needed to better understand the spatial dynamics of these important respiratory viruses in humans.

Replacement of neuraminidase inhibitor-susceptible influenza A(H1N1) with resistant phenotype in 2008 and circulation of susceptible influenza A and B viruses during 2009-2013, South Africa.

BACKGROUND: Data on the susceptibility of influenza viruses from South Africa to neuraminidase inhibitors (NAIs) are scarce, and no extensive analysis was done. OBJECTIVES: We aimed to determine oseltamivir and zanamivir susceptibility of influenza A and B virus neuraminidases (NAs), 2007-2013, South Africa. PATIENTS/METHODS: We enrolled participants through national influenza-like illness surveillance, 2007-2013. Influenza diagnosis was by virus isolation and quantitative polymerase chain reaction (qPCR). Drug susceptibility was determined by chemiluminescence-based NA-STAR/NA-XTD assay. Sanger sequencing was used to determine molecular markers of NAI resistance. RESULTS: Forty percent (6341/15 985) of participants were positive for influenza viruses using virus isolation (2007-2009) and qPCR (2009-2013) methods. A total of 1236/6341 (19.5%) virus isolates were generated of which 307/1236 (25%) were tested for drug susceptibility. During 2007-2008, the median 50% inhibitory concentration (IC50 ) of oseltamivir for seasonal influenza A(H1N1) increased from of 0.08 nmol/L (range 0.01-3.60) in 2007 to 73 nmol/L (range 1.56-305 nmol/L) in 2008. Influenza A isolates from 2009 to 2013 were susceptible to oseltamivir [A(H3N2) median IC50  = 0.05 nmol/L (range 0.01-0.08); A(H1N1)pdm09 = 0.11 nmol/L (range 0.01-0.78)] and zanamivir [A(H3N2) median IC50  = 0.56 nmol/L (range 0.47-0.66); A(H1N1)pdm09 = 0.35 nmol/L (range 0.27-0.533)]. Influenza B viruses were susceptible to both NAIs. NAI resistance-associated substitutions H275Y, E119V, and R150K (N1 numbering) were not detected in influenza A viruses that circulated in 2009-2013. CONCLUSIONS: We confirm replacement of NAI susceptible by resistant phenotype influenza A(H1N1) in 2008. Influenza A and B viruses (2009-2013) remained susceptible to NAIs; therefore, these drugs are useful for treating influenza-infected patients.

Risk of Human Infections With Highly Pathogenic H5N2 and Low Pathogenic H7N1 Avian Influenza Strains During Outbreaks in Ostriches in South Africa.

Background: Risk factors for human infection with highly pathogenic (HP) and low-pathogenic (LP) avian influenza (AI) H5N2 and H7N1 were investigated during outbreaks in ostriches in the Western Cape province, South Africa. Methods: Serum surveys were conducted for veterinarians, farmworkers, and laboratory and abattoir workers involved in 2 AI outbreaks in the Western Cape province: (1) controlling and culling of 42000 ostriches during (HPAI)H5N2 outbreaks in ostriches (2011) (n = 207); (2) movement control during (LPAI)H7N1 outbreaks in 2012 (n = 66). A third serosurvey was conducted on state veterinarians from across the country in 2012 tasked with disease control in general (n = 37). Antibodies to H5 and H7 were measured by means of hemagglutination inhibition and microneutralization assays, with microneutralization assay titers >40 considered positive. Results: Two of 207 (1%) participants were seropositive for H5 and 4 of 207 (2%) for H7 in 2011, compared with 1 of 66 (1.5%) and 8 of 66 (13%) in 2012. Although individuals in all professions tested seropositive, abattoir workers (10 of 97; 10.3%) were significantly more at risk of influenza A(H7N1) infection (P = .001) than those in other professions (2 of 171;1.2%). Among state veterinarians, 4 of 37(11%) were seropositive for H7 and 1 of 37 (2.7%) for H5. Investigations of (LP)H7N1-associated fatalities in wild birds and quarantined exotic birds in Gauteng, AI outbreaks in poultry in KwaZulu-Natal, and ostriches in Western Cape province provide possible exposure events. Conclusion: (LPAI)H7N1 strains pose a greater infection-risk than (HPAI)H5N2 strains to persons involved in control of outbreaks in infected birds, with ostrich abattoir workers at highest risk.

Epidemiology of influenza B/Yamagata and B/Victoria lineages in South Africa, 2005-2014.

BACKGROUND: Studies describing the epidemiology of influenza B lineages in South Africa are lacking. METHODS: We conducted a prospective study to describe the circulation of influenza B/Victoria and B/Yamagata lineages among patients of all ages enrolled in South Africa through three respiratory illness surveillance systems between 2005 and 2014: (i) the Viral Watch (VW) program enrolled outpatients with influenza-like illness (ILI) from private healthcare facilities during 2005-2014; (ii) the influenza-like illnesses program enrolled outpatients in public healthcare clinics (ILI/PHC) during 2012-2014; and (iii) the severe acute respiratory illnesses (SARI) program enrolled inpatients from public hospitals during 2009-2014. Influenza B viruses were detected by virus isolation during 2005 to 2009 and by real-time reverse transcription polymerase chain reaction from 2009-2014. Clinical and epidemiological characteristics of patients hospitalized with SARI and infected with different influenza B lineages were also compared using unconditional logistic regression. RESULTS: Influenza viruses were detected in 22% (8,706/39,804) of specimens from patients with ILI or SARI during 2005-2014, of which 24% (2,087) were positive for influenza B. Influenza B viruses predominated in all three surveillance systems in 2010. B/Victoria predominated prior to 2011 (except 2008) whereas B/Yamagata predominated thereafter (except 2012). B lineages co-circulated in all seasons, except in 2013 and 2014 for SARI and ILI/PHC surveillance. Among influenza B-positive SARI cases, the detection of influenza B/Yamagata compared to influenza B/Victoria was significantly higher in individuals aged 45-64 years (adjusted odds ratio [aOR]: 4.2; 95% confidence interval [CI]: 1.1-16.5) and ≥65 years (aOR: 12.2; 95% CI: 2.3-64.4) compared to children aged 0-4 years, but was significantly lower in HIV-infected patients (aOR: 0.4; 95% CI: 0.2-0.9). CONCLUSION: B lineages co-circulated in most seasons except in 2013 and 2014. Hospitalized SARI cases display differential susceptibility for the two influenza B lineages, with B/Victoria being more prevalent among children and HIV-infected persons.

Evaluation of influenza vaccine effectiveness and description of circulating strains in outpatient settings in South Africa, 2014.

The effectiveness of the trivalent seasonal influenza vaccine during the 2014 season in South Africa was assessed using a test-negative case-control study design including 472 cases and 362 controls. Influenza A(H3N2) was the dominant strain circulating. The overall vaccine effectiveness estimate, adjusted for age and underlying conditions, was 43·1% (95% CI: -26·8-74·5). 2014 H3N2 viruses from South Africa were mainly in sublineage 3C.3 with accumulation of amino acid changes that differentiate them from the vaccine strain in 3C.1.

Effectiveness and knowledge, attitudes and practices of seasonal influenza vaccine in primary healthcare settings in South Africa, 2010-2013.

OBJECTIVES: Influenza vaccine effectiveness (VE) and coverage data for sub-Saharan Africa are scarce. Using a test-negative case-control design, we estimated influenza VE annually among individuals with influenza-like illness presenting to an outpatient sentinel surveillance programme in South Africa from 2010 to 2013. A knowledge, attitudes and practices (KAP) influenza vaccine survey of programme clinicians was conducted in 2013. SAMPLE: In total, 9420 patients were enrolled in surveillance of whom 5344 (56.7%) were included in the VE analysis: 2678 (50.1%) were classified as controls (influenza test-negative) and 2666 (49.9%) as cases (influenza test-positive). RESULTS: Mean annual influenza vaccine coverage among controls was 4.5% for the four years. Annual VE estimates adjusted for age, underlying medical conditions and seasonality for 2010-2013 were 54.2% (95% confidence interval (CI): 2.4-78.6%), 57.1% (95% CI: 15.5-78.2%), 38.4% (95% CI: -71.7-78.1%) and 87.2% (95% CI: 67.2-95.0%), respectively. The KAP survey showed that >90% of clinicians were familiar with the indications for and the benefits of influenza vaccination. CONCLUSIONS: Our study showed that the vaccine was significantly protective in 2010, 2011 and 2013, but not in 2012 when the circulating A(H3N2) strain showed genetic drift. Vaccine coverage was low despite good clinician knowledge of vaccination indications. Further studies are needed to investigate the reason for the low uptake of influenza vaccine.

Influenza epidemiology and vaccine effectiveness among patients with influenza-like illness, viral watch sentinel sites, South Africa, 2005-2009.

BACKGROUND: There is limited data on the epidemiology of influenza and few published estimates of influenza vaccine effectiveness (VE) from Africa. In April 2009, a new influenza virus strain infecting humans was identified and rapidly spread globally. We compared the characteristics of patients ill with influenza A(H1N1)pdm09 virus to those ill with seasonal influenza and estimated influenza vaccine effectiveness during five influenza seasons (2005-2009) in South Africa. METHODS: Epidemiological data and throat and/or nasal swabs were collected from patients with influenza-like illness (ILI) at sentinel sites. Samples were tested for seasonal influenza viruses using culture, haemagglutination inhibition tests and/or polymerase chain reaction (PCR) and for influenza A(H1N1)pdm09 by real-time PCR. For the vaccine effectiveness (VE) analysis we considered patients testing positive for influenza A and/or B as cases and those testing negative for influenza as controls. Age-adjusted VE was calculated as 1-odds ratio for influenza in vaccinated and non-vaccinated individuals. RESULTS: From 2005 through 2009 we identified 3,717 influenza case-patients. The median age was significantly lower among patients infected with influenza A(H1N1)pdm09 virus than those with seasonal influenza, 17 and 27 years respectively (p<0.001). The vaccine coverage during the influenza season ranged from 3.4% in 2009 to 5.1% in 2006 and was higher in the ≥50 years (range 6.9% in 2008 to 13.2% in 2006) than in the <50 years age group (range 2.2% in 2007 to 3.7% in 2006). The age-adjusted VE estimates for seasonal influenza were 48.6% (4.9%, 73.2%); -14.2% (-9.7%, 34.8%); 12.0% (-70.4%, 55.4%); 67.4% (12.4%, 90.3%) and 29.6% (-21.5%, 60.1%) from 2005 to 2009 respectively. For the A(H1N1)pdm09 season, the efficacy of seasonal vaccine was -6.4% (-93.5%, 43.3%). CONCLUSION: Influenza vaccine demonstrated a significant protective effect in two of the five years evaluated. Low vaccine coverage may have reduced power to estimate vaccine effectiveness.