T cell responses to SARS-CoV-2 spike cross-recognize Omicron.

The SARS-CoV-2 Omicron variant (B.1.1.529) has multiple spike protein mutations1,2 that contribute to viral escape from antibody neutralization3-6 and reduce vaccine protection from infection7,8. The extent to which other components of the adaptive response such as T cells may still target Omicron and contribute to protection from severe outcomes is unknown. Here we assessed the ability of T cells to react to Omicron spike protein in participants who were vaccinated with Ad26.CoV2.S or BNT162b2, or unvaccinated convalescent COVID-19 patients (n = 70). Between 70% and 80% of the CD4+ and CD8+ T cell response to spike was maintained across study groups. Moreover, the magnitude of Omicron cross-reactive T cells was similar for Beta (B.1.351) and Delta (B.1.617.2) variants, despite Omicron harbouring considerably more mutations. In patients who were hospitalized with Omicron infections (n = 19), there were comparable T cell responses to ancestral spike, nucleocapsid and membrane proteins to those in patients hospitalized in previous waves dominated by the ancestral, Beta or Delta variants (n = 49). Thus, despite extensive mutations and reduced susceptibility to neutralizing antibodies of Omicron, the majority of T cell responses induced by vaccination or infection cross-recognize the variant. It remains to be determined whether well-preserved T cell immunity to Omicron contributes to protection from severe COVID-19 and is linked to early clinical observations from South Africa and elsewhere9-12.

Standardized Phylogenetic Classification of Human Respiratory Syncytial Virus below the Subgroup Level.

A globally implemented unified phylogenetic classification for human respiratory syncytial virus (HRSV) below the subgroup level remains elusive. We formulated global consensus of HRSV classification on the basis of the challenges and limitations of our previous proposals and the future of genomic surveillance. From a high-quality curated dataset of 1,480 HRSV-A and 1,385 HRSV-B genomes submitted to GenBank and GISAID (https://www.gisaid.org) public sequence databases through March 2023, we categorized HRSV-A/B sequences into lineages based on phylogenetic clades and amino acid markers. We defined 24 lineages within HRSV-A and 16 within HRSV-B and provided guidelines for defining prospective lineages. Our classification demonstrated robustness in its applicability to both complete and partial genomes. We envision that this unified HRSV classification proposal will strengthen HRSV molecular epidemiology on a global scale.

Survey of West Nile and Banzi Viruses in Mosquitoes, South Africa, 2011-2018.

We collected >40,000 mosquitoes from 5 provinces in South Africa during 2011-2018 and screened for zoonotic flaviviruses. We detected West Nile virus in mosquitoes from conservation and periurban sites and potential new mosquito vectors; Banzi virus was rare. Our results suggest flavivirus transmission risks are increasing in South Africa.

Shuni Virus in Cases of Neurologic Disease in Humans, South Africa.

We describe Shuni virus (SHUV) detection in human neurologic disease cases in South Africa. SHUV RNA was identified in 5% of cerebrospinal fluid specimens collected during the arbovirus season from public sector hospitals. This finding suggests that SHUV may be a previously unrecognized cause of human neurologic infections in Africa.

Potential Mosquito Vectors for Shuni Virus, South Africa, 2014-2018.

Shuni virus is associated with neurologic and febrile illness in animals and humans. To determine potential vectors, we collected mosquitoes in South Africa and detected the virus in species of the genera Mansonia, Culex, Aedes, and Anopheles. These mosquitoes may be associated with Shuni virus outbreaks in Africa and emergence in other regions.

The African Network for Improved Diagnostics, Epidemiology and Management of common infectious Agents.

BACKGROUND: In sub-Saharan Africa, acute respiratory infections (ARI), acute gastrointestinal infections (GI) and acute febrile disease of unknown cause (AFDUC) have a large disease burden, especially among children, while respective aetiologies often remain unresolved. The need for robust infectious disease surveillance to detect emerging pathogens along with common human pathogens has been highlighted by the ongoing novel coronavirus disease 2019 (COVID-19) pandemic. The African Network for Improved Diagnostics, Epidemiology and Management of Common Infectious Agents (ANDEMIA) is a sentinel surveillance study on the aetiology and clinical characteristics of ARI, GI and AFDUC in sub-Saharan Africa. METHODS: ANDEMIA includes 12 urban and rural health care facilities in four African countries (Côte d'Ivoire, Burkina Faso, Democratic Republic of the Congo and Republic of South Africa). It was piloted in 2018 in Côte d'Ivoire and the initial phase will run from 2019 to 2021. Case definitions for ARI, GI and AFDUC were established, as well as syndrome-specific sampling algorithms including the collection of blood, naso- and oropharyngeal swabs and stool. Samples are tested using comprehensive diagnostic protocols, ranging from classic bacteriology and antimicrobial resistance screening to multiplex real-time polymerase chain reaction (PCR) systems and High Throughput Sequencing. In March 2020, PCR testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and analysis of full genomic information was included in the study. Standardised questionnaires collect relevant clinical, demographic, socio-economic and behavioural data for epidemiologic analyses. Controls are enrolled over a 12-month period for a nested case-control study. Data will be assessed descriptively and aetiologies will be evaluated using a latent class analysis among cases. Among cases and controls, an integrated analytic approach using logistic regression and Bayesian estimation will be employed to improve the assessment of aetiology and associated risk factors. DISCUSSION: ANDEMIA aims to expand our understanding of ARI, GI and AFDUC aetiologies in sub-Saharan Africa using a comprehensive laboratory diagnostics strategy. It will foster early detection of emerging threats and continued monitoring of important common pathogens. The network collaboration will be strengthened and site diagnostic capacities will be reinforced to improve quality management and patient care.

Zoonotic Alphaviruses in Fatal and Neurologic Infections in Wildlife and Nonequine Domestic Animals, South Africa.

Alphaviruses from Africa, such as Middelburg virus (MIDV), and Sindbis virus (SINV), were detected in horses with neurologic disease in South Africa, but their host ranges remain unknown. We investigated the contribution of alphaviruses to neurologic infections and death in wildlife and domestic animals in this country. During 2010-2018, a total of 608 clinical samples from wildlife and nonequine domestic animals that had febrile, neurologic signs or unexplained deaths were tested for alphaviruses. We identified 32 (5.5%) of 608 alphavirus infections (9 SINV and 23 MIDV), mostly in neurotissue of wildlife, domestic animals, and birds. Phylogenetic analysis of the RNA-dependent RNA polymerase gene confirmed either SINV or MIDV. This study implicates MIDV and SINV as potential causes of neurologic disease in wildlife and nonequine domestic species in Africa and suggests a wide host range and pathogenic potential.

Shuni Virus in Wildlife and Nonequine Domestic Animals, South Africa.

We screened nonequine animals with unexplained neurologic signs or death in South Africa during 2010-2018 for Shuni virus (SHUV). SHUV was detected in 3.3% of wildlife, 1.1% of domestic, and 2.0% of avian species. Seropositivity was also demonstrated in wildlife. These results suggest a range of possible SHUV hosts in Africa.

The Fraction of Rhinovirus Detections Attributable to Mild and Severe Respiratory Illness in a Setting of High Human Immunodeficiency Virus Prevalence, South Africa, 2013-2015.

BACKGROUND: The association of rhinovirus (RV) detection to illness is poorly understood. METHODS: We enrolled case patients hospitalized with severe respiratory illness (SRI) at 2 hospitals and outpatients with influenza-like illness (ILI) and asymptomatic individuals (controls) from 2 affiliated clinics during 2013-2015. We compared the RV prevalence among ILI and SRI cases to those of controls stratified by human immunodeficiency virus (HIV) serostatus using penalized logistic regression. The attributable fraction (AF) was calculated. RESULTS: During 2013-2015, RV was detected in 17.4% (368/2120), 26.8% (979/3654), and 23.0% (1003/4360) of controls, ILI cases, and SRI cases, respectively. The RV AF (95% confidence interval) was statistically significant among children aged <5 years (ILI: 44.6% [30.7%-55.7%] and SRI: 50.3% [38.6%-59.9%]; P < .001) and individuals aged ≥5 years (ILI: 62.9% [54.4%-69.8%] and SRI: 51.3% [38.7%-61.3%]; P < .001) as well as among HIV-infected (ILI: 59.9% [45.8%-70.3%] and SRI: 39.8% [22.3%-53.3%]; P < .001) and HIV-uninfected (ILI: 53.6% [44.7%-61.1%] and SRI: 55.3% [45.6%-63.2%]; P < .001) individuals. CONCLUSIONS: Although RV detection was common among controls, it was also associated with a substantial proportion of clinical illness across age groups, irrespective of HIV status.

Household Transmission of Seasonal Influenza From HIV-Infected and HIV-Uninfected Individuals in South Africa, 2013-2014.

BACKGROUND: We estimated the household secondary infection risk (SIR) and serial interval (SI) for influenza transmission from HIV-infected and HIV-uninfected index cases. METHODS: Index cases were the first symptomatic person in a household with influenza-like illness, testing influenza positive on real-time reverse transcription polymerase chain reaction (rRT-PCR). Nasopharyngeal swabs collected from household contacts every 4 days were tested by rRT-PCR. Factors associated with SIR were evaluated using logistic regression. RESULTS: We enrolled 28 HIV-infected and 57 HIV-uninfected index cases. On multivariable analysis, HIV-infected index cases were less likely to transmit influenza to household contacts (odds ratio [OR] 0.2; 95% confidence interval [CI], 0.1-0.6; SIR 16%, 18/113 vs 27%, 59/220). Factors associated with increased SIR included index age group 1-4 years (OR 3.6; 95% CI, 1.2-11.3) and 25-44 years (OR 8.0; 95% CI, 1.8-36.7), and contact age group 1-4 years (OR 3.5; 95% CI, 1.2-10.3) compared to 5-14 years, and sleeping with index case (OR 2.7; 95% CI, 1.3-5.5). HIV infection of index case was not associated with SI. CONCLUSIONS: HIV-infection was not associated with SI. Increased infectiousness of HIV-infected individuals is likely not an important driver of community influenza transmission.

The Role of Human Immunodeficiency Virus in Influenza- and Respiratory Syncytial Virus-associated Hospitalizations in South African Children, 2011-2016.

BACKGROUND: Data describing influenza- or respiratory syncytial virus (RSV)-associated hospitalized illness in children aged <5 years in Africa are limited. METHODS: During 2011-2016, we conducted surveillance for severe respiratory illness (SRI) in children aged <5 years in 3 South African hospitals. Nasopharyngeal aspirates were tested for influenza and RSV using real-time reverse transcription polymerase chain reaction. We estimated rates of influenza- and RSV-associated hospitalized SRI by human immunodeficiency virus (HIV) status and compared children who tested positive for influenza vs RSV using multivariable penalized logistic regression. RESULTS: Among 3650 hospitalized children, 203 (5.6%) tested positive for influenza viruses, 874 (23.9%) for RSV, and 19 (0.5%) for both. The median age of children hospitalized with influenza was 13.9 months vs 4.4 months for RSV (P < .01). Annual influenza-associated hospitalization rates per 100000 were highest among infants aged 6-11 months (545; 95% confidence interval [CI], 409-703), while RSV-associated hospitalization rates were highest in infants aged 0-2 months (6593; 95% CI, 5947-7217). HIV exposure was associated with increased incidence of influenza- and RSV-associated hospitalization in infants aged 0-5 months, with relative risk (RR) 2.2 (95% CI, 1.4-3.4) and 1.4 (95% CI, 1.3-1.6), respectively. HIV infection was associated with increased incidence of influenza- and RSV-associated hospitalization in all age groups; RR 2.7 (95% CI, 2.0-3.5) and 3.8 (95% CI, 3.1-4.8), respectively. CONCLUSIONS: Influenza- and RSV-associated hospitalizations are common among South African infants. HIV infection and HIV exposure in infants increase risk of influenza- and RSV-associated hospitalization.

The Impact of Human Immunodeficiency Virus Exposure on Respiratory Syncytial Virus-associated Severe Respiratory Illness in South African Infants, 2011-2016.

From 2011 through 2016, we conducted surveillance for severe respiratory illness in infants. Human immunodeficiency virus exposure significantly increased the risk of respiratory syncytial virus (RSV)-associated hospitalization in infants aged <5 months. More than 60% of RSV-associated hospitalizations occurred in the first 4 months of life and may be preventable through maternal vaccination or birth-dose monoclonal antibody.

Bagaza Virus in Himalayan Monal Pheasants, South Africa, 2016-2017.

Bagaza virus (BAGV) has not been reported in birds in South Africa since 1978. We used phylogenetic analysis and electron microscopy to identify BAGV as the likely etiology in neurologic disease and death in Himalayan monal pheasants in Pretoria, South Africa. Our results suggest circulation of BAGV in South Africa.

West Nile Virus in Wildlife and Nonequine Domestic Animals, South Africa, 2010-2018.

West Nile virus (WNV) lineage 2 is associated with neurologic disease in horses and humans in South Africa. Surveillance in wildlife and nonequine domestic species during 2010-2018 identified WNV in 11 (1.8%) of 608 animals with severe neurologic and fatal infections, highlighting susceptible hosts and risk for WNV epizootics in Africa.

Influenza Viral Shedding in a Prospective Cohort of HIV-Infected and Uninfected Children and Adults in 2 Provinces of South Africa, 2012-2014.

Background: Prolonged shedding of influenza viruses may be associated with increased transmissibility and resistance mutation acquisition due to therapy. We compared duration and magnitude of influenza shedding between human immunodeficiency virus (HIV)-infected and -uninfected individuals. Methods: A prospective cohort study during 3 influenza seasons enrolled patients with influenza-like illness and a positive influenza rapid test. Influenza viruses were detected by real-time reverse transcription polymerase chain reaction. Weibull accelerated failure time regression models were used to describe influenza virus shedding. Mann-Whitney U tests explored initial influenza viral loads (VL). Results: Influenza virus shedding duration was similar in 65 HIV-infected (6 days; interquartile range [IQR] 3-10) and 176 HIV-uninfected individuals (7 days; IQR 4-11; P = .97), as was initial influenza VL (HIV-uninfected 5.28 ± 1.33 log10 copies/mL, HIV-infected 4.73 ± 1.68 log10 copies/mL; P = .08). Adjusted for age, HIV-infected individuals with low CD4 counts shed influenza virus for longer than those with higher counts (adjusted hazard ratio 3.55; 95% confidence interval, 1.05-12.08). Discussion: A longer duration of influenza virus shedding in HIV-infected individuals with low CD4 counts may suggest a possible increased risk for transmission or viral evolution in severely immunocompromised individuals. HIV-infected individuals should be prioritized for annual influenza immunization.

Distribution of influenza virus types by age using case-based global surveillance data from twenty-nine countries, 1999-2014.

BACKGROUND: Influenza disease burden varies by age and this has important public health implications. We compared the proportional distribution of different influenza virus types within age strata using surveillance data from twenty-nine countries during 1999-2014 (N=358,796 influenza cases). METHODS: For each virus, we calculated a Relative Illness Ratio (defined as the ratio of the percentage of cases in an age group to the percentage of the country population in the same age group) for young children (0-4 years), older children (5-17 years), young adults (18-39 years), older adults (40-64 years), and the elderly (65+ years). We used random-effects meta-analysis models to obtain summary relative illness ratios (sRIRs), and conducted meta-regression and sub-group analyses to explore causes of between-estimates heterogeneity. RESULTS: The influenza virus with highest sRIR was A(H1N1) for young children, B for older children, A(H1N1)pdm2009 for adults, and (A(H3N2) for the elderly. As expected, considering the diverse nature of the national surveillance datasets included in our analysis, between-estimates heterogeneity was high (I2>90%) for most sRIRs. The variations of countries' geographic, demographic and economic characteristics and the proportion of outpatients among reported influenza cases explained only part of the heterogeneity, suggesting that multiple factors were at play. CONCLUSIONS: These results highlight the importance of presenting burden of disease estimates by age group and virus (sub)type.

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.

West Nile Virus Lineage 2 in Horses and Other Animals with Neurologic Disease, South Africa, 2008-2015.

During 2008-2015 in South Africa, we conducted West Nile virus surveillance in 1,407 animals with neurologic disease and identified mostly lineage 2 cases in horses (7.4%, 79/1,069), livestock (1.5%, 2/132), and wildlife (0.5%, 1/206); 35% were fatal. Geographic correlation of horse cases with seropositive veterinarians suggests disease in horses can predict risk in humans.