States with better sanitation more at risk to Covid? Theory needs testing

Studies and data indicate that the hygiene hypothesis may be at play, but experts say that there are more factors influencing deaths

David P Strachan, in his 1989 seminal paper “Hay fever, hygiene and household size”, proposed that lower incidence of infection in early childhood could be an explanation for the rise in allergic diseases such as hay fever. Popularly called the hygiene hypothesis, Strachan’s formulations have since been tested for various diseases and infections.

Hygiene hypothesis is popular again as developing countries and low-income economies have shown more resilience to SARS-Cov-2—the virus that causes Covid-19--than the developed world. Data emanating from the economies suggests this much. The developed world has witnessed more deaths per million than the developing economies.

Researchers, at the start