Background Between March and December, 2020, more than 20 000 laboratory-confirmed cases of SARS-CoV-2 infection were reported in Zambia. However, the number of SARS-CoV-2 infections is likely to be higher than the confirmed case counts because many infected people have mild or no symptoms, and limitations exist with regard to testing capacity and surveillance systems in Zambia. We aimed to estimate SARS-CoV-2 prevalence in six districts of Zambia in July, 2020, using a population-based household survey. Methods Between July 4 and July 27, 2020, we did a cross-sectional cluster-sample survey of households in six districts of Zambia. Within each district, 16 standardised enumeration areas were randomly selected as primary sampling units using probability proportional to size. 20 households from each standardised enumeration area were selected using simple random sampling. All members of selected households were eligible to participate. Consenting participants completed a questionnaire and were tested for SARS-CoV-2 infection using real-time PCR (rtPCR) and anti-SARS-CoV-2 antibodies using ELISA. Prevalence estimates, adjusted for the survey design, were calculated for each diagnostic test separately, and combined. We applied the prevalence estimates to census population projections for each district to derive the estimated number of SARS-CoV-2 infections. Findings Overall, 4258 people from 1866 households participated in the study. The median age of participants was 18•2 years (IQR 7•7-31•4) and 50•6% of participants were female. SARS-CoV-2 prevalence for the combined measure was 10•6% (95% CI 7•3-13•9). The rtPCR-positive prevalence was 7•6% (4•7-10•6) and ELISA-positive prevalence was 2•1% (1•1-3•1). An estimated 454 708 SARS-CoV-2 infections (95% CI 312 705-596 713) occurred in the six districts between March and July, 2020, compared with 4917 laboratory-confirmed cases reported in official statistics from the Zambia National Public Health Institute. Interpretation The estimated number of SARS-CoV-2 infections was much higher than the number of reported cases in six districts in Zambia. The high rtPCR-positive SARS-CoV-2 prevalence was consistent with observed community transmission during the study period. The low ELISA-positive SARS-CoV-2 prevalence might be associated with mitigation measures instituted after initial cases were reported in March, 2020. Zambia should monitor patterns of SARS-CoV-2 prevalence and promote measures that can reduce transmission. Funding US Centers for Disease Control and Prevention.

Abstract. We conducted a prospective cohort study of 496 adults starting antiretroviral treatment (ART) to determine the impact of neuropsychiatric symptoms and socioeconomic status on adherence and mortality. Almost 60% had good adherence based upon pharmacy records. Poor adherence was associated with being divorced, poorer, food insecure, and less educated. Longer travel time to clinic, concealing one's human immunodeficiency virus (HIV) status, and experiencing side effects predicted poor adherence. Over a third of the patients had cognitive impairment and poorer cognitive function was also associated with poor adherence. During follow-up (mean 275 days), 20% died-usually within 90 days of starting ART. Neuropsychiatric symptoms, advanced HIV, peripheral neuropathy symptoms, food insecurity, and poverty were associated with death. Neuropsychiatric symptoms, advanced HIV, and poverty remained significant independent predictors of death in a multivariate model adjusting for other significant factors. Social, economic, cognitive, and psychiatric problems impact adherence and survival for people receiving ART in rural Zambia.

To the Editor: Killed oral cholera vaccines (OCVs) are part of the standard response package to a cholera outbreak, although the two-dose regimen of vaccines that has been prequalified by the World Health Organization (WHO) poses challenges to timely and efficient reactive vaccination campaigns. 1 Recent data suggest that the first dose alone provides short-term protection, similar to that of two doses, which may largely dictate the effect of OCVs during epidemics. [2][3][4] A cholera outbreak was detected in Lusaka, Zambia, in February 2016, after a period of 4 years without a reported case of cholera. An emergency reactive vaccination campaign was implemented in April 2016, targeting more than 500,000 persons who were at high risk for cholera in Lusaka (population, >2 million persons). The Ministry of Health, with support from Médecins sans Frontières and the WHO, decided to implement a single-dose campaign to quell the epidemic rapidly, in view of the insufficient number of vaccine doses that were available in the global stockpile to complete a two-dose campaign. In December 2016, when more doses became available, a second round of vaccination was organized and the second vaccine dose was offered to persons at risk.We conducted a matched case-control study to quantify the short-term effectiveness of a single-dose OCV regimen (Shanchol) between April 25, 2016, and June 15, 2016. The study was approved by two institutional review boards, and written informed consent was obtained from all the participants (see the Supplementary Appendix, available with the full text of this letter at NEJM.org). Cases of cholera were confirmed by means of culture, polymerase-chain-reaction as-

We conducted a retrospective chart review of antiretroviral therapy (ART) clinic patients treated during the first 12 months after clinics opened in rural Zambia and assessed adherence based on clinic attendance, patient report, and staff assessment. We identified 255 eligible patients (mean age, 39.7 years; 44.3% male; 56.5% married; and 45.5% with only primary school education). Twenty percent had partners known to be HIV positive. Twenty percent were widowed. Thirty-seven percent had disclosed their HIV status to their spouse. Disclosure was less likely among women (27.5% versus 49.6%, P = 0.0005); 36.5% had "clinic buddies" to provide adherence support. Adherence rates were good for 59.2%. Disclosure of HIV status to ones' spouse (P = 0.047), knowing spouses' HIV status (P = 0.02), and having a clinic buddy (P = 0.01) were associated with good adherence. Social support is a key patient-level resource impacting ART adherence in rural Zambia. Limited spousal disclosure affects women more than men. Clinic buddies are associated with better adherence.

Investment in SARS-CoV-2 sequencing in Africa over the past year has led to a major increase in the number of sequences generated, now exceeding 100,000 genomes, used to track the pandemic on the continent. Our results show an increase in the number of African countries able to sequence domestically, and highlight that local sequencing enables faster turnaround time and more regular routine surveillance. Despite limitations of low testing proportions, findings from this genomic surveillance study underscore the heterogeneous nature of the pandemic and shed light on the distinct dispersal dynamics of Variants of Concern, particularly Alpha, Beta, Delta, and Omicron, on the continent. Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve, while the continent faces many emerging and re-emerging infectious disease threats. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century.