Rainfall anomalies and typhoid fever in Blantyre, Malawi

Epidemiol Infect. 2022 May 10;150:e122. doi: 10.1017/S0950268822000759.


Typhoid fever is a major cause of illness and mortality in low- and middle-income settings. We investigated the association of typhoid fever and rainfall in Blantyre, Malawi, where multi-drug-resistant typhoid has been transmitting since 2011. Peak rainfall preceded the peak in typhoid fever by approximately 15 weeks [95% confidence interval (CI) 13.3, 17.7], indicating no direct biological link. A quasi-Poisson generalised linear modelling framework was used to explore the relationship between rainfall and typhoid incidence at biologically plausible lags of 1-4 weeks. We found a protective effect of rainfall anomalies on typhoid fever, at a two-week lag (P = 0.006), where a 10 mm lower-than-expected rainfall anomaly was associated with up to a 16% reduction in cases (95% CI 7.6, 26.5). Extreme flooding events may cleanse the environment of S. Typhi, while unusually low rainfall may reduce exposure from sewage overflow. These results add to evidence that rainfall anomalies may play a role in the transmission of enteric pathogens, and can help direct future water and sanitation intervention strategies for the control of typhoid fever.

Keywords: Typhoid fever; rainfall; statistical analysis; weather.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Drug Resistance, Multiple
  • Humans
  • Incidence
  • Malawi / epidemiology
  • Poisson Distribution
  • Poverty
  • Rain*
  • Sanitation
  • Social Class
  • Typhoid Fever / epidemiology*
  • Typhoid Fever / prevention & control