Syndromic surveillance with monthly aggregate health systems information data for COVID-19 pandemic response in Neno, Malawi: a monitoring study

BACKGROUND: In the context of diminutive COVID-19 screening and testing, syndromic surveillance can be used to identify areas with higher-than-expected SARS-CoV-2 symptoms for targeted public health interventions. We used syndromic surveillance to monitor potential SARS-CoV-2 outbreaks in 14 health facilities in the Neno district of rural Malawi. METHODS: We monitored three indicators identified as potential symptoms of SARS-CoV-2 infection: the proportion of outpatient visits for fast-breathing cases in children under 5 years (FBC<5); the proportion of suspected malaria cases confirmed as non-malaria in children under 5 years (NMC<5); and the same indicator in individuals aged 5 years and older (NMC≥5). We extracted data aggregated by month and at the health facility-level from the District Health Information System. With data from January, 2016, to February, 2020, as a baseline, we used a linear model with a negative binomial distribution to estimate expected proportions for the indicators in absence of the COVID-19 pandemic with 95% prediction intervals (PI) for March, 2020, to July, 2021. We compared the observed proportions to the expected rates, focusing on the first two waves of infections (June to July, 2020, and January to March, 2021). FINDINGS: The proportion of FBC<5 was consistently higher than expected, with a peak in May, 2020, when 2·5% of outpatient visits were fast breathing cases in children younger than 5 years of age (compared with the expected rate of 0·8% [95% PI 0·4–1·5]). NMC<5 was as expected throughout the study period. The NMC≥5 indicator remained as expected, except for increases in suspected cases tested negative for malaria, to 31·3% (from the expected 18·6% [95% PI 12·3–28·7]) in November, 2020, and to 32·5% (from the expected 21·7% [95% PI 14·2–32·2]) in July, 2021. INTERPRETATION: An increase in FBC<5 and NMC≥5 before observed COVID-19 waves might indicate SARS-CoV-2 infections that were missed before robust testing. This tendency was not seen in NMC<5, which can represent differences in symptomatology leading to decreased health-seeking behaviours for this age group. Syndromic surveillance can allow for real-time responses at facilities, including increased and focused testing and screening to identify potential SARS-CoV-2 infections. FUNDING: Supported by Canadian Institutes of Health Research.