COVID-19 places ‘hygiene speculation’ to check

A city bath in Bihar used for bathing, washing, and other domestic purposes. The new study associates a low COVID-19 death rate with poor access to water, sanitation and hygiene. Photo credit: Melissa Cooperman / IFPRI ( (CC BY-NC-SA 2.0, -nc-sa / 2.0 /)

Indian researchers from the impressive Council for Scientific and Industrial Research (CSIR) and two other institutes tested the “hygienic hypothesis” with a study suggesting that areas with high infectious disease prevalence are likely to have fewer COVID-19 deaths.

They cite the fact that Bihar state, notorious for having the worst human development indices in that country of 1.3 billion people, has so far reported a COVID death rate of 0.5 percent, which is about a third of the national average.

The study, published October 19 in MedRxiv, awaits peer review, but boldly states, “Paradoxically, better hygiene results in poorer immune training and, therefore, could result in higher deaths per million.”

In particular, while various development parameters were included in the study, the worse the water and sanitation indices, the lower the deaths per million.

This seems to be a blow to the hygiene hypothesis, which states that as the frequency of infection decreases in industrialized and developing countries, there is a corresponding increase in allergies and autoimmune diseases.

However, the study must warn against using poor hygiene as a strategy in dealing with COVID-19 or other diseases. “While we provide a possible explanation based on sanitary practices of the differences in CFR (death rate) between economically stronger and weaker countries, this should not be inferred as our advocacy of moving towards weaker sanitary practices to deal with future pandemics.”

So what are the researchers pushing? They are looking for new opportunities for “immune training” and for microbiome therapies that can complement conventional sanitary and hygienic practices.

Previous studies have also indicated that exposure to pathogens boosts the immune system against infection, but this has yet to stand up to scrutiny. Indeed, research in sub-Saharan Africa awaiting peer review again associates higher COVID-19 death rates with poor access to WASH, the acronym for water, sanitation and sanitation.

Anyone seeking solace in India’s situation with poor WASH indices is doomed to disappointment. India has made efforts to eliminate open defecation and other practices associated with high levels of waterborne infections associated with stunts and preventable infections.

A quick review by a colleague, Manu Raj, professor and senior consultant at the Amrita Institute for Medical Sciences and Research Center, Kochi, Kerala, found that the study has too many assumptions. “I’m sure the second wave will destroy all of your conclusions and new assumptions will come into play,” Raj told SciDev.Net.

“The main hurdle for such data is that poor countries have no accuracy for variables we use in the model. These are just some of the assumptions, while in rich countries these are more accurate,” says Raj, referring to “differentiated reporting” of deaths from countries like China, Iran, Russia, Turkey and many Latin American countries. “

“The corona scene is very volatile and most of the early assumptions are gone,” says Raj. “I would just say looks interesting, but we’ll take a second look after the second wave.”

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More information:
Bithika Chatterjee et al. Mortality from COVID-19 in different countries is related to the demographic nature of the countries and the prevalence of autoimmunity (2020). DOI: 10.1101 / 2020.07.31.20165696

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Quote: COVID-19 puts the hygiene hypothesis to the test (2020, November 2nd), which was accessed on November 2nd, 2020 from

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