Respiratory viruses in rural Zambia before and during the COVID-19 pandemic.

OBJECTIVES: With the emergence of the COVID-19 pandemic, restrictions were implemented globally to control the virus. Data on respiratory pathogens in sub-Saharan Africa during the COVID-19 pandemic are scarce. This analysis was conducted to evaluate patterns of respiratory pathogens in rural Zambia before and during the first year of the pandemic. METHODS: Surveillance was established in December 2018 at Macha Hospital in southern Zambia. Patients with respiratory symptoms in the outpatient and inpatient clinics were recruited. Nasopharyngeal samples were collected and tested for respiratory pathogens. The prevalence of respiratory symptoms and pathogens was evaluated and compared in the first (December 10, 2018-December 9, 2019) and second (December 10, 2019-November 30, 2020) years of surveillance. RESULTS: Outpatient visits and admissions for respiratory illness significantly decreased from the first to second year, especially among children. SARS-CoV-2 was not detected from any participants in Year 2. Among outpatients and inpatients with respiratory symptoms, the prevalence of respiratory syncytial virus and influenza viruses decreased from the first to second year. In contrast, the prevalence of rhinovirus/enterovirus, metapneumovirus and parainfluenza virus increased. CONCLUSIONS: The epidemiology of respiratory viruses in rural Zambia changed during the first year of the COVID-19 pandemic, suggesting that public health interventions may have had an impact on the introduction and circulation of respiratory pathogens in this area.

Estimated incidence and transmission intensity of rubella infection in Zambia pre-vaccine era 2005-2016.

The rubella disease burden in Zambia may be under-estimated. Using models, we describe the transmission dynamics, determine the incidence estimates and assess the level of underestimation of the real burden of rubella infection in Zambia during the pre-vaccination period 2005-2016. This study used both the deterministic compartmental model and likelihood-based method using a Bayesian framework to describe the epidemiology of rubella. A total of 1313 cases of rubella were confirmed with the highest annual number of 255 new cases recorded in 2008. However, 2014 recorded the highest monthly median positivity rate of 9.0%. The observed median rubella cases were 5.5. There was a seasonal pattern in the occurrence of laboratory-confirmed rubella, with higher test positivity rates of rubella infection usually recorded in the months of September, October and November. The modelled monthly median incidence of rubella infection among the general population was 76 and 20 among pregnant women. The incidence of rubella among the non-pregnant women was 44. The average effective reproductive number (Rt) between 2005 and 2016 was estimated as 1.2 with the peak of infection occurring in 2016. The measles surveillance system underestimates the observed burden of rubella. A mass vaccination campaign conducted between January and July is recommended.

Facility-based surveillance for influenza and respiratory syncytial virus in rural Zambia.

BACKGROUND: While southern Africa experiences among the highest mortality rates from respiratory infections, the burden of influenza and respiratory syncytial virus (RSV) in rural areas is poorly understood. METHODS: We implemented facility-based surveillance in Macha, Zambia. Outpatients and inpatients presenting with influenza-like illness (ILI) underwent testing for influenza A, influenza B, and RSV and were prospectively followed for 3 to 5 weeks to assess clinical course. Log-binomial models assessed correlates of infection and clinical severity. RESULTS: Between December 2018 and December 2019, 17% of all outpatients presented with ILI and 16% of inpatients were admitted with an acute respiratory complaint. Influenza viruses and RSV were detected in 17% and 11% of outpatient participants with ILI, and 23% and 16% of inpatient participants with ILI, respectively. Influenza (July-September) and RSV (January-April) prevalence peaks were temporally distinct. RSV (relative risk [RR]: 1.78; 95% confidence interval [CI] 1.51-2.11), but not influenza, infection was associated with severe disease among patients with ILI. Underweight patients with ILI were more likely to be infected with influenza A (prevalence ratio [PR]: 1.72; 95% CI 1.04-2.87) and to have severe influenza A infections (RR: 2.49; 95% CI 1.57-3.93). CONCLUSIONS: Populations in rural Zambia bear a sizeable burden of viral respiratory infections and severe disease. The epidemiology of infections in this rural area differs from that reported from urban areas in Zambia.

First 100 Persons with COVID-19 - Zambia, March 18-April 28, 2020.

Zambia is a landlocked, lower-middle income country in southern Africa, with a population of 17 million (1). The first known cases of coronavirus disease 2019 (COVID-19) in Zambia occurred in a married couple who had traveled to France and were subject to port-of-entry surveillance and subsequent remote monitoring of travelers with a history of international travel for 14 days after arrival. They were identified as having suspected cases on March 18, 2020, and tested for COVID-19 after developing respiratory symptoms during the 14-day monitoring period. In March 2020, the Zambia National Public Health Institute (ZNPHI) defined a suspected case of COVID-19 as 1) an acute respiratory illness in a person with a history of international travel during the 14 days preceding symptom onset; or 2) acute respiratory illness in a person with a history of contact with a person with laboratory-confirmed COVID-19 in the 14 days preceding symptom onset; or 3) severe acute respiratory illness requiring hospitalization; or 4) being a household or close contact of a patient with laboratory-confirmed COVID-19. This definition was adapted from World Health Organization (WHO) interim guidance issued March 20, 2020, on global surveillance for COVID-19 (2) to also include asymptomatic contacts of persons with confirmed COVID-19. Persons with suspected COVID-19 were identified through various mechanisms, including port-of-entry surveillance, contact tracing, health care worker (HCW) testing, facility-based inpatient screening, community-based screening, and calls from the public into a national hotline administered by the Disaster Management and Mitigation Unit and ZNPHI. Port-of-entry surveillance included an arrival screen consisting of a temperature scan, report of symptoms during the preceding 14 days, and collection of a history of travel and contact with persons with confirmed COVID-19 in the 14 days before arrival in Zambia, followed by daily remote telephone monitoring for 14 days. Travelers were tested for SARS-CoV-2, the virus that causes COVID-19, if they were symptomatic upon arrival or developed symptoms during the 14-day monitoring period. Persons with suspected COVID-19 were tested as soon as possible after evaluation for respiratory symptoms or within 7 days of last known exposure (i.e., travel or contact with a confirmed case). All COVID-19 diagnoses were confirmed using real-time reverse transcription-polymerase chain reaction (RT-PCR) testing (SARS-CoV-2 Nucleic Acid Detection Kit, Maccura) of nasopharyngeal specimens; all patients with confirmed COVID-19 were admitted into institutional isolation at the time of laboratory confirmation, which was generally within 36 hours. COVID-19 patients were deemed recovered and released from isolation after two consecutive PCR-negative test results ≥24 hours apart. A Ministry of Health memorandum was released on April 13, 2020, mandating testing in public facilities of 1) all persons admitted to medical and pediatric wards regardless of symptoms; 2) all patients being admitted to surgical and obstetric wards, regardless of symptoms; 3) any outpatient with fever, cough, or shortness of breath; and 4) any facility or community death in a person with respiratory symptoms, and 5) biweekly screening of all HCWs in isolation centers and health facilities where persons with COVID-19 had been evaluated. This report describes the first 100 COVID-19 cases reported in Zambia, during March 18-April 28, 2020.

Epidemiology of acute rubella infection in Zambia during the pre-vaccination period (2005-2016) as a baseline for monitoring rubella epidemiology in the post-rubella vaccine introduction era.

BACKGROUND: Rubella is highly under reported in Zambia as in most sub-Saharan countries despite being a disease of major public health concern especially among women of childbearing age. In September 2016, Zambia introduced a combined measles-rubella vaccine in children 0-14 years. In this study, we estimated the proportion positive for acute rubella among suspected but negative measles cases between 2005 and 2016 and determined its correlates for monitoring rubella epidemiology post-rubella vaccine introduction. METHODS: In a retrospective study, 4497 measles IgM negative serum samples from 5686 clinically suspected measles cases were examined for rubella IgM antibodies using the Siemens, Enzygnost® ELISA kit at the national measles laboratory. Data on demographics, year and month of onset were extracted from the surveillance data. Multivariate logistic regression analysis using backward variable selection was conducted to determine independent predictors for acute rubella. The magnitude of association was estimated using adjusted odds ratio with a 95% confidence interval. RESULTS: Overall, a proportion of 29.2% (1313/4497) affecting mostly those between 5 and 24 years was determined. Only age, province, month and year were independently associated with acute rubella. The regional proportions varied from 21.8-37.3% peaking in the month of October. Persons in the age group 10-14 years (Adjusted Odds Ratio [AOR] = 2.43; 95% CI [2.01-2.95]) were more likely while those aged < 1 year less likely (AOR = 0.31; 95% CI [021-0.48]) to have acute rubella compared to those aged 25 years or older. Persons in 2010 were less likely (AOR = 0.12; CI [0.05, 0.28]) to have acute rubella compared to those in 2016. While acute rubella was more likely to occur between July and November compared to December, it was less likely to occur between February and May. CONCLUSIONS: Rubella virus was circulating in Zambia between 2005 and 2016 affecting mostly persons in the age group 5-24 years peaking in the hot dry season month of October. Although vaccination against rubella has been launched, these baseline data are important to provide a reference point when determining the impact of the vaccination program implemented.

An evaluation of the Zambia influenza sentinel surveillance system, 2011-2017.

BACKGROUND: Over the past decade, influenza surveillance has been established in several African countries including Zambia. However, information on the on data quality and reliability of established influenza surveillance systems in Africa are limited. Such information would enable countries to assess the performance of their surveillance systems, identify shortfalls for improvement and provide evidence of data reliability for policy making and public health interventions. METHODS: We used the Centers for Disease Control and Prevention guidelines to evaluate the performance of the influenza surveillance system (ISS) in Zambia during 2011-2017 using 9 attributes: (i) data quality and completeness, (ii) timeliness, (iii) representativeness, (iv) flexibility, (v) simplicity, (vi) acceptability, (vii) stability, (viii) utility, and (ix) sustainability. Each attribute was evaluated using pre-defined indicators. For each indicator we obtained the proportion (expressed as percentage) of the outcome of interest over the total. A scale from 1 to 3 was used to provide a score for each attribute as follows: < 60% (as obtained in the calculation above) scored 1 (weak performance); 60-79% scored 2 (moderate performance); ≥80% scored 3 (good performance). An overall score for each attribute and the ISS was obtained by averaging the scores of all evaluated attributes. RESULTS: The overall mean score for the ISS in Zambia was 2.6. Key strengths of the system were the quality of data generated (score: 2.9), its flexibility (score: 3.0) especially to monitor viral pathogens other than influenza viruses, its simplicity (score: 2.8), acceptability (score: 3.0) and stability (score: 2.6) over the review period and its relatively low cost ($310,000 per annum). Identified weaknesses related mainly to geographic representativeness (score: 2.0), timeliness (score: 2.5), especially in shipment of samples from remote sites, and sustainability (score: 1.0) in the absence of external funds. CONCLUSIONS: The system performed moderately well in our evaluation. Key improvements would include improvements in the timeliness of samples shipments and geographical coverage. However, these improvements would result in increased cost and logistical complexity. The ISSS in Zambia is largely reliant on external funds and the acceptability of maintaining the surveillance system through national funds would require evaluation.

Lujo viral hemorrhagic fever: considering diagnostic capacity and preparedness in the wake of recent Ebola and Zika virus outbreaks.

Lujo virus is a novel Old World arenavirus identified in Southern Africa in 2008 as the cause of a viral hemorrhagic fever (VHF) characterized by nosocomial transmission with a high case fatality rate of 80% (4/5 cases). Whereas this outbreak was limited, the unprecedented Ebola virus disease outbreak in West Africa, and recent Zika virus disease epidemic in the Americas, has brought into acute focus the need for preparedness to respond to rare but potentially highly pathogenic outbreaks of zoonotic or arthropod-borne viral infections. A key determinant for effective control of a VHF outbreak is the time between primary infection and diagnosis of the index case. Here, we review the Lujo VHF outbreak of 2008 and discuss how preparatory measures with respect to developing diagnostic capacity might be effectively embedded into existing national disease control networks, such as those for human immunodeficiency virus, tuberculosis, and malaria.

Impact of Rotavirus Vaccination on Diarrheal Hospitalizations in Children Aged <5 Years in Lusaka, Zambia.

BACKGROUND: Monovalent rotavirus vaccine was introduced in the routine public health immunization program in Lusaka, Zambia, in January 2012 and was rolled out countrywide in November 2013. We examined the effect of rotavirus vaccination on hospitalization for all-cause acute gastroenteritis (AGE) and rotavirus-specific AGE at a large referral hospital in Lusaka. METHODS: Data were derived from ongoing hospital-based AGE surveillance from January 2009 to December 2014. Pre-rotavirus vaccine introduction (2009-2011) and post-rotavirus vaccine introduction (2013-2014) periods were compared for annual changes in hospitalizations for AGE and rotavirus; 2012 was excluded as a transition year. Hospital administrative discharge data were used to compare trends in all-cause diarrhea discharges and in-hospital diarrhea deaths captured by HIMS pre- and post-rotavirus vaccine introduction. RESULTS: Between January 2009 and December 2014, 5937 children <5 years of age presenting with AGE had their stools collected and tested for rotavirus by enzyme immunoassay. The rotavirus positivity rate declined from 40.1% (449/1121) in prevaccine years to 30.2% (250/828;P< .001) in 2013 and 24.7% (157/635;P< .001) in 2014. The greatest reduction was noted in infants, with the rotavirus positivity rate in this age group declining from 40.9% in prevaccine years to 34.0% (P= .009) in 2013 and 26.2% (P< .001) in 2014. Following rotavirus vaccine introduction, seasonal peaks of rotavirus and all-cause AGE were dwarfed. From HIMS data, compared to the prevaccine era, reductions of 18%-29% in all-cause diarrhea hospitalizations and 27%-33% in-hospital diarrhea deaths among children <1 year of age were observed in 2013 and 2014. CONCLUSIONS: We observed a significant reduction in AGE-associated in-hospital morbidity and mortality following rotavirus vaccine introduction. The greatest reduction was seen in infants <1 year who accounted for 84.4% of rotavirus hospitalizations prior to vaccine introduction.

Identification of viral and bacterial pathogens from hospitalized children with severe acute respiratory illness in Lusaka, Zambia, 2011-2012: a cross-sectional study.

BACKGROUND: Morbidity and mortality from respiratory infections are higher in resource-limited countries than developed countries, but limited studies have been conducted in resource-limited settings to examine pathogens from patients with acute respiratory infections. Influenza surveillance has been conducted in Zambia since 2008; however, only 4.3% of patients enrolled in 2011-2012 were positive for influenza. Therefore, we examined non-influenza respiratory pathogens in children with severe acute respiratory illness (SARI) in Zambia, to estimate the scope of disease burden and determine commonly-identified respiratory pathogens. METHODS: Two reverse transcriptase polymerase chain reaction (rRT-PCR) methods (single and multiplex) were used to analyze nasopharyngeal and throat swabs collected from SARI cases under five years of age from January 2011 through December 2012. All specimens were negative for influenza by rRT-PCR. The panel of singleplex reactions targeted seven viruses, while the multiplex assay targeted thirty-three bacteria, fungi, and viruses. RESULTS: A set of 297 specimens were tested by singleplex rRT-PCR, and a different set of 199 were tested by multiplex rRT-PCR. Using the singleplex assay, 184/297 (61.9%) specimens were positive for one or more viruses. The most prevalent viruses were human rhinovirus (57/297; 19.2%), human adenovirus (50/297; 16.8%), and respiratory syncytial virus (RSV) (45/297; 15.2%). Using multiplex PCR, at least one virus was detected from 167/199 (83.9%) specimens, and at least one bacteria was detected from 197/199 (99.0%) specimens. Cytomegalovirus (415/199; 208.5%) and RSV (67/199; 33.7%) were the most commonly detected viruses, while Streptococcus pneumonie (109/199; 54.8%) and Moraxella catarrhalis (92/199; 46.2%) were the most commonly detected bacteria. CONCLUSIONS: Single infections and co-infections of many viruses and bacteria were identified in children with SARI. These results provide an estimate of the prevalence of infection and show which respiratory pathogens are commonly identified in patients. Further studies should investigate causal associations between individual pathogens and SARI.

First sero-prevalence of dengue fever specific immunoglobulin G antibodies in Western and North-Western provinces of Zambia: a population based cross sectional study.

BACKGROUND: Dengue fever is a tropical infectious disease caused by dengue virus (DENV), a single positive-stranded RNA Flavivirus. There is no published evidence of dengue in Zambia. The objective of the study was to determine the sero-prevalence and correlates for dengue fever specific IgG antibodies in Western and North-Western provinces in Zambia. METHODS: A randomized cluster design was used to sample participants for yellow fever risk assessment. In order to rule out cross reactivity with other flaviviruses including dengue, differential antibody tests were done by ELISA. Data was processed using Epi Data version 3.1 and transferred to SPSS version 16.0 for analysis. Bivariate and multivariate analyses were performed to determine the association of dengue fever with various factors. Unadjusted odds ratios (OR), adjusted odds ratios (AOR) and their 95% confidence intervals (CI) are reported. RESULTS: A total of 3,624 persons were sampled for dengue virus infection of whom 53.3% were female and 23.9% were in the 5-14 years age group. Most persons in the survey attained at least primary education (47.6%). No significant association was observed between sex and dengue virus infection (p = 1.000). Overall, 4.1% of the participants tested positive for Dengue IgG. In multivariate analysis, the association of age with Dengue infection showed that those below 5 years of age were 63% (AOR = 0.37; 95% CI [0.16, 0.86]) less likely to be infected with Dengue virus compared to those aged 45 years or older. A significant association was observed between grass thatched roofing and Dengue infection (AOR = 2.28; 95% CI [1.15, 4.53]) Respondents who used Insecticide Treated Nets (ITN) were 21% (AOR = 1.21; 95% CI [1.01, 1.44]) more likely to be infected with dengue infection than those who did not use ITNs. Meanwhile, participants who visited Angola were 73% (AOR = 1.73; 95% CI [1.27, 2.35]) more likely to be infected with Dengue virus than those who did not visit Angola. CONCLUSION: This study provides the first evidence of dengue infection circulation in both North-Western and Western provinces of Zambia. It is important that surveillance activities for Dengue and diagnostic systems are expanded and strengthened, nationwide in order to capture information related to dengue virus and other flaviviruses.

Characterization of human respiratory syncytial virus in children with severe acute respiratory infection before and during the COVID-19 pandemic.

Objectives: Annual outbreaks of human respiratory syncytial virus (HRSV) are caused by newly introduced and locally persistent strains. During the COVID-19 pandemic, global and local circulation of HRSV significantly decreased. This study was conducted to characterize HRSV in 2018-2022 and to analyze the impact of COVID-19 on the evolution of HRSV. Design/methods: Combined oropharyngeal and nasopharyngeal swabs were collected from children hospitalized with severe acute respiratory infection at two hospitals in Zambia. The second hypervariable region of the attachment gene G was targeted for phylogenetic analysis. Results: Of 3113 specimens, 504 (16.2%) were positive for HRSV, of which 131 (26.0%) and 66 (13.1%) were identified as HRSVA and HRSVB, respectively. In early 2021, an increase in HRSV was detected, caused by multiple distinct clades of HRSVA and HRSVB. Some were newly introduced, whereas others resulted from local persistence. Conclusions: This study provides insights into the evolution of HRSV, driven by global and local circulation. The COVID-19 pandemic had a temporal impact on the evolution pattern of HRSV. Understanding the evolution of HRSV is vital for developing strategies for its control.

COVID-19 mortality sentinel surveillance at a tertiary referral hospital in Lusaka, Zambia, 2020-2021.

Deaths from COVID-19 likely exceeded official statistics in Zambia because of limited testing and incomplete death registration. We describe a sentinel COVID-19 mortality surveillance system in Lusaka, Zambia. We analyzed surveillance data on deceased persons of all ages undergoing verbal autopsy (VA) and COVID-19 testing at the University Teaching Hospital (UTH) mortuary in Lusaka, Zambia, from April 2020 through August 2021. VA was done by surveillance officers for community deaths and in-patient deaths that occurred <48 hours after admission. A standardized questionnaire about the circumstances proximal to death was used, with a probable cause of death assigned by a validated computer algorithm. Nasopharyngeal specimens from deceased persons were tested for COVID-19 using polymerase chain reaction and rapid diagnostic tests. We analyzed the cause of death by COVID-19 test results. Of 12,919 deceased persons at UTH mortuary during the study period, 5,555 (43.0%) had a VA and COVID-19 test postmortem, of which 79.7% were community deaths. Overall, 278 (5.0%) deceased persons tested COVID-19 positive; 7.1% during waves versus 1.4% during nonwave periods. Most (72.3%) deceased persons testing COVID-19 positive reportedly had fever, cough, and/or dyspnea and most (73.5%) reportedly had an antemortem COVID-19 test. Common causes of death for those testing COVID-19 positive included acute cardiac disease (18.3%), respiratory tract infections (16.5%), other types of cardiac diseases (12.9%), and stroke (7.2%). A notable portion of deceased persons at a sentinel site in Lusaka tested COVID-19 positive during waves, supporting the notion that deaths from COVID-19 might have been undercounted in Zambia. Many had displayed classic COVID-19 symptoms and been tested before death yet nevertheless died in the community, potentially indicating strained medical services during waves. The high proportion of cardiovascular diseases deaths might reflect the hypercoagulable state during severe COVID-19. Early supportive treatment and availability of antivirals might lessen future mortality.

Comparison of HIV prevalence, incidence, and viral load suppression in Zambia population-based HIV impact assessments from 2016 and 2021.

BACKGROUND: The Zambian government has implemented a public health response to control the HIV epidemic in the country. Zambia conducted a population-based HIV impact assessment (ZAMPHIA) survey in 2021 to assess the status of the HIV epidemic to guide its public health programs. METHODS: ZAMPHIA 2021 was a cross-sectional two-stage cluster sample household survey among persons aged ≥15 years conducted in Zambia across all 10 provinces. Consenting participants were administered a standardized questionnaire and whole blood was tested for HIV according to national guidelines. HIV-1 viral load (VL), recent HIV infection, and antiretroviral medications were tested for in HIV-seropositive samples. Viral load suppression (VLS) was defined as <1000 copies/ml. ZAMPHIA 2021 results were compared to ZAMPHIA 2016 for persons aged 15-59 years (i.e., the overlapping age ranges). All estimates were weighted to account for nonresponse and survey design. RESULTS: During ZAMPHIA 2021, of 25 483 eligible persons aged ≥15 years, 18 804 (73.8%) were interviewed and tested for HIV. HIV prevalence was 11.0% and VLS prevalence was 86.2% overall, but was <80% among people living with HIV aged 15-24 years and in certain provinces. Among persons aged 15-59 years, from 2016 to 2021, HIV incidence declined from 0.6% to 0.3% ( P -value: 0.07) and VLS prevalence increased from 59.2% to 85.7% ( P -value: <0.01). DISCUSSION: Zambia has made substantial progress toward controlling the HIV epidemic from 2016 to 2021. Continued implementation of a test-and-treat strategy, with attention to groups with lower VLS in the ZAMPHIA 2021, could support reductions in HIV incidence and improve overall VLS in Zambia.

Influenza surveillance in Zambia, 2008-2009.

BACKGROUND: Limited information exists about influenza viruses in Africa. We used data from a new sentinel surveillance system to investigate the seasonality and characteristics of influenza, including pandemic (pdm) influenza A H1N1, in Zambia. METHODS: In June 2008, we established sentinel surveillance for influenza-like illness (ILI) and severe acute respiratory illness (SARI) at 4 healthcare facilities in Zambia. Nasopharyngeal and oropharyngeal swabs and structured questionnaires were collected from eligible patients and samples were tested by real-time reverse-transcription polymerase chain reaction for influenza virus types and subtypes. RESULTS: From June 2008 to December 2009, we collected 1234 specimens, of which 334 (27%) were ILI, and 900 (63%) were SARI. Overall, 4% (57) of specimens were positive for influenza. The influenza detection rate in ILI and SARI cases was 5% (17/334) and 4% (40/900), respectively. Among all influenza cases, 54 (95%) were influenza A and 3 (5%) were influenza B. Of the influenza A viruses, 16 (30%) were A(H1N1)pdm09, 29 (54%) were seasonal A(H1N1), 6 (11%) were A(H3N2), and 4 (7%) were unsubtyped. The detection rate for A(H1N1)pdm09 cases was highest in persons aged 5-24 years (5/98; 5%), 25-44 years (4/78; 5%), and 45-64 years (1/17; 6%). Conversely, for seasonal influenza the detection rate was highest in children aged 1-4 years (18/294; 6%). Influenza virus circulation peaked during June-August in both years and A(H1N1)pdm09 occurred at the end of the influenza season in 2009. CONCLUSIONS: Seasonal influenza virus infection was found to be associated with both mild and severe respiratory illness in Zambia. Future years of surveillance are necessary to better define the seasonality and epidemiology of influenza in the country.

Respiratory viruses in rural Zambia during the second year of the COVID-19 pandemic.

Objectives: Limited data on respiratory infections are available from sub-Saharan Africa during the COVID-19 pandemic. The objective of this study was to evaluate the burden of respiratory viruses in rural Zambia from 2019-2021. Methods: Surveillance was initiated at Macha Hospital in Zambia in December 2018. Each week, patients with respiratory symptoms were enrolled from the outpatient clinic. Nasopharyngeal samples were collected and tested for respiratory pathogens. The prevalence of respiratory symptoms and viruses in 2021 was compared to results from 2019 and 2020. Results: After seeing few cases of influenza virus and respiratory syncytial virus in 2020, a return to prepandemic levels was observed in 2021. Rhinovirus/enterovirus, parainfluenza virus 1-4, and adenovirus circulated from 2019 to 2021, while human metapneumovirus and human coronaviruses (HKU1, 229E, OC43, and NL63 subtypes) were observed sporadically. SARS-CoV-2 was observed consistently in 2021 after being first identified in December 2020. The proportion of participants with co-infections in 2021 (11.6%) was significantly higher than in 2019 (6.9%) or 2020 (7.7%). Conclusion: Declines in influenza virus and respiratory syncytial virus were reversed once public health measures were lifted. Respiratory viruses contributed to a significant burden of respiratory infections in 2021. This study provides important information about respiratory viruses in this changing context and underrepresented region.

Measles immunity gaps among children and adolescents with HIV in Zambia despite high measles vaccination and antiretroviral therapy coverage.

OBJECTIVE: The study objective was to identify measles and rubella immunity gaps among people with HIV (PWH) in Zambia despite high measles vaccine coverage and widespread access to antiretroviral therapy. DESIGN: Nationally representative cross-sectional serosurvey using biorepository specimens. METHODS: Blood specimens collected in the Zambia Population HIV Impact Assessment survey (ZAMPHIA) of 2016 were tested for measles and rubella immunoglobulin G (IgG) antibodies by enzyme immunoassay. Hierarchical generalized additive models were fit to characterize age-specific measles and rubella seroprevalence profiles by HIV infection status. Log-binomial regression was performed to identify factors associated with seronegativity. RESULTS: Of the 25 383 specimens, a subsample of 11 500 were selected and 9852 (85%) were successfully tested. Measles seroprevalence was lower among PWH compared with HIV-uninfected individuals until approximately 30 years of age. Among children younger than the age of 10 years, measles seroprevalence was 47.2% [95% confidence interval (CI): 32.7, 61.7] in PWH and 76.4% (95% CI: 74.9, 78.0) in HIV-uninfected children in same age category. In contrast, rubella seroprevalence was higher among PWH than HIV-uninfected individuals, particularly for children younger than 10 years (68.6% vs. 44.3%, P  < 0.001). Having a detectable viral load was associated with being measles seronegative (adjusted prevalence ratio 0.15, 95% CI: 0.06, 0.38). CONCLUSIONS: These results from a nationally representative serosurvey demonstrate persistence of measles immunity gaps among PWH younger than 30 years of age. There is need to implement the World Health Organization's recommendation to revaccinate children living with HIV against measles following immune reconstitution with antiretroviral therapy to protect these children and prevent measles outbreaks.

Uptake of public health measures and vaccine acceptance during the COVID-19 pandemic in rural Zambia.

Vaccines are effective tools to prevent COVID-19-related morbidity. However, coverage is low throughout sub-Saharan Africa. Uptake of public health measures, perceptions of COVID-19 illness and vaccines, and intention to vaccinate were evaluated in 2021-2022 in rural Zambia. Adherence to public health measures, perceptions of COVID-19 risk and severity, and vaccine acceptance increased significantly over time, particularly in December 2021, coinciding with the fourth pandemic wave and relaunch of the national vaccine campaign. Vaccine acceptance was associated with perceptions of vaccine safety and effectiveness, but not disease severity. These findings highlight the importance of strong pandemic response and public communication for increased uptake of mitigatory measures, including vaccine acceptance.

Leveraging a national biorepository in Zambia to assess measles and rubella immunity gaps across age and space.

High-quality, representative serological surveys allow direct estimates of immunity profiles to inform vaccination strategies but can be costly and logistically challenging. Leveraging residual serum samples is one way to increase their feasibility. We subsampled 9854 residual sera from a 2016 national HIV survey in Zambia and tested these specimens for anti-measles and anti-rubella virus IgG antibodies using indirect enzyme immunoassays. We demonstrate innovative methods for sampling residual sera and analyzing seroprevalence data, as well as the value of seroprevalence estimates to understand and control measles and rubella. National measles and rubella seroprevalence for individuals younger than 50 years was 82.8% (95% CI 81.6, 83.9%) and 74.9% (95% CI 73.7, 76.0%), respectively. Despite a successful childhood vaccination program, measles immunity gaps persisted across age groups and districts, indicating the need for additional activities to complement routine immunization. Prior to vaccine introduction, we estimated a rubella burden of 96 congenital rubella syndrome cases per 100,000 live births. Residual samples from large-scale surveys can reduce the cost and challenges of conducting serosurveys, and multiple pathogens can be tested. Procedures to access quality specimens, ensure ethical approvals, and link sociodemographic data can improve the timeliness and value of results.

Genomic Surveillance of SARS-CoV-2 in the Southern Province of Zambia: Detection and Characterization of Alpha, Beta, Delta, and Omicron Variants of Concern.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern (VOCs) have significantly impacted the global epidemiology of the pandemic. From December 2020 to April 2022, we conducted genomic surveillance of SARS-CoV-2 in the Southern Province of Zambia, a region that shares international borders with Botswana, Namibia, and Zimbabwe and is a major tourist destination. Genetic analysis of 40 SARS-CoV-2 whole genomes revealed the circulation of Alpha (B.1.1.7), Beta (B.1.351), Delta (AY.116), and multiple Omicron subvariants with the BA.1 subvariant being predominant. Whereas Beta, Delta, and Omicron variants were associated with the second, third, and fourth pandemic waves, respectively, the Alpha variant was not associated with any wave in the country. Phylogenetic analysis showed evidence of local transmission and possible multiple introductions of SARS-CoV-2 VOCs in Zambia from different European and African countries. Across the 40 genomes analysed, a total of 292 mutations were observed, including 182 missense mutations, 66 synonymous mutations, 23 deletions, 9 insertions, 1 stop codon, and 11 mutations in the non-coding region. This study stresses the need for the continued monitoring of SARS-CoV-2 circulation in Zambia, particularly in strategically positioned regions such as the Southern Province which could be at increased risk of introduction of novel VOCs.

Impact of a Measles and Rubella Vaccination Campaign on Seroprevalence in Southern Province, Zambia.

Zambia conducted a measles and rubella (MR) vaccination campaign targeting children 9 months to younger than 15 years of age in 2016. This campaign was the first introduction of a rubella-containing vaccine in Zambia. To evaluate the impact of the campaign, we compared the MR seroprevalence estimates from serosurveys conducted before and after the campaign in Southern Province, Zambia. The measles seroprevalence increased from 77.8% (95% confidence interval [CI], 73.2-81.9) to 96.4% (95% CI, 91.7-98.5) among children younger than 15 years. The rubella seroprevalence increased from 51.3% (95% CI, 45.6-57.0) to 98.3% (95% CI, 95.5-99.4). After the campaign, slightly lower seroprevalence remained for young adults 15 to 19 years old, who were not included in the campaign because of their age. These serosurveys highlighted the significant impact of the vaccination campaign and identified immunity gaps for those beyond the targeted vaccination age. Continued monitoring of population immunity can signal the need for future targeted vaccination strategies.