Low Covid-19 fatality rates in countries with poor hygiene, low-quality water: study

Health workers wearing personal protective equipment (PPE) conduct health check-ups of residents of Poddar Wadi Slum for the detection of COVID-19 cases in Mumbai (PTI)

A new study has found that countries with poor hygiene and sanitation and low-quality water have a lower Covid-19 fatality rate as compared to richer countries where sanitation quality is high. Until now, scientists have wondered at the higher prevalence of infection and deaths from Covid-19 in richer countries as opposed to poorer ones.

While the findings indicate that the poorer the water sanitation in a country, the lower the Covid-19 deaths per million, the study has strongly advised against pursuing weak hygiene as a disease coping mechanism. Demography, improved hygiene and higher incidence of autoimmune disorders correlated positively with Covid-19 mortality and were among the most plausible factors to explain it as compared to GDP of the countries, said Dr Shekhar Mande, director general, Council of Scientific and Industrial Research (CSIR).

“Researchers from Pune’s National Centre for Cell Science (NCCS) and Chennai Mathematical Institute conducted a statistical analysis and examined more than 25 to 30 parameters, including water, sanitation and Covid-19 deaths patients per million in 106 countries,” Mande told The Indian Express.

“One of the primary manifestations of Covid-19 has been a severe autoimmune reaction in the later phase of the disease. Among the reasons for rising prevalence in autoimmune disorders in western countries is proposed to be related to the ‘hygiene hypothesis’,” said Mande, who is the co-author of the study ‘The mortality due to Covid-19 in different nations is associated with the demographic character of nations and the prevalence of autoimmunity’, published on MedRxiv..

Paradoxically, better sanitation leads to poor “immune training” and this hypothesis postulates that exposure to pathogens early in life protects people from allergic diseases later in life. Better hygiene practices could lower a person’s immunity and make him or her susceptible to autoimmune diseases. Improvement in hygiene practices such as better sanitation, availability of safe drinking water, hand washing facilities and others reduces the impact of communicable diseases. On the contrary, such a reduction to exposure to infectious agents might be related to higher prevalence of autoimmune disorders, researchers have noted.

Researchers Bithika Chatterjee from NCCS and Rajeeva Laxman Karandikar from Chennai Mathematical Institute examined developmental parameters like demography, prevalence of communicable and non-communicable diseases, BCG vaccination status, sanitation and Covid-19 deaths per million in the 106 countries. Researchers ran multivariate linear regression models to discover that the incidence of communicable diseases correlated negatively while demography, improved hygiene and higher incidence of autoimmune disorders correlated positively with Covid-19 mortality.

“Statistical evidence should give a head start to investigate the role of hyper immune reaction on Covid-19 susceptibility at the individual patient’s level and this analysis opens up avenues to consider immune training with possibility of microbiome therapies to supplement improved hygiene and sanitation practices,” Mande said.

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