Covid-19, Nepal and the hygiene hypothesis


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Children at a government school in western Nepal eating lunch. © Marty Logan

This article was published on the Nepali Times website on Monday, and got a huge amount of interest (9,000+ page views in less than 24 hours). There was a lot of criticism, at least on Twitter, that the ‘hygiene hypothesis’ that is discussed should not have been broached now because it has not been scientifically proven.
I disagree because the idea has been floating around and discussed informally since the outbreak began, and I think it’s better that it be given a public airing than ignored. What do readers think?

“It just doesn’t make sense!” You might have heard this phrase more than once lately in the context of Nepal and COVID-19: next to the epicentre in Wuhan and host to a large number of Chinese tourists and residents, this country has still only recorded one case of the coronavirus, and the person recovered. How can that be?

You might also have heard, and scoffed, at the rumour that Nepalis have superior immune systems. ‘Nepali people have a stronger immunity power’ was one reason given in this article for why COVID-19 has not hit the country yet. As time goes on and the number of cases remains at just one, could there actually be something to the claim?

“The whole world is raising the question of Nepal because of the lack of COVID-19 cases and especially after the country recorded only three deaths from two previous virus outbreaks originating in China — SARS in 2002 and the 2009 H1N1,” says Baburam Marasini, former director of the Epidemiology and Disease Control Division of the Department of Health Services.

“I believe that more cases of COVID-19 would have been detected by now if there was an active surveillance system in place,” added Marasini who says he has advised health officials to test people already hospitalised for pneumonia or with major breathing difficulties. “If you compare the number of those people with the number from last year you will see they have increased and have indirect proof that the virus is here.”

No reports of increased cases

Meanwhile, Sameer Dixit of the Centre for Molecular Dynamics says he has done that comparison and in the past four months there has been no increase in reports of flu-like illnesses to the Epidemiology and Disease Control Division compared to previous years. Across the country 20-25 government, private and community hospitals report to the division via the Early Warning and Response System.

Yet based on experiences in other countries to date, 10-15% of those infected with COVID-19 should become seriously ill. Asks Dixit: “The limited testing to date could be a major factor, but don’t you think that there should be huge spikes everywhere of severe illness among the elderly population? It’s not happening. At night I lie in bed wondering why, and it’s bothering the hell out of me.”

Dixit, who has postgraduate degrees in immunology and biotechnology, believes that people are not getting seriously ill because Nepal is experiencing a less severe strain of the virus, and/or Nepalis do have stronger immune systems.

“While lack of testing is also a big cause for missing cases, I believe that immunity may be a major player in developing countries. I know this sounds far-fetched, and people will laugh when they hear it, but there is a ‘hygiene hypothesis’.”

‘Hygiene hypothesis’

The theory suggests that people who grow up in less hygienic surroundings develop strong immunity to external health threats. Dixit notes that the hypothesis has not been tested for virus outbreaks.

But to support the hygiene hypothesis he notes figures from previous outbreaks:

  • 2009 Influenza A H1N1 pandemic: Global infected 700 million -1.4 billion, Global deaths 150,000-600,000, Nepal: Infected 173, Deaths 3.
  • 2003 SARS Corona outbreak: Global infected ~8,000, Global deaths ~770, Nepal: Infected 0, Deaths 0.

Buddha Basnyat, a physician at Patan Hospital, downright rejects the notion of ‘Nepali immunity’. He says: “I think it is foolhardy to think that we are somehow immune – there is no scientific basis for this. I think it is a silly, wild conjecture.”

He adds: “I hope it does not happen here, I hope all of these theories about immunity are true, but this is not a one-off virus, I think. Our health system is in a shambles, I think we should just make plans for a disaster.”

Dixit, however, is not convinced that wider testing is necessary. “Developing countries like Nepal have a limited number of tests. It is very hard to justify testing among the 80-85% of people who could develop mild symptoms — how would we find them anyway? You’d basically have to go door-to-door and how practical is that … we basically need to save lives. Screw the detective work.”

Instead, Dixit counsels trying to identify the 10-15% of the population most at risk, suggesting that people might have been hospitalised and mistakenly diagnosed with Influenza A when they actually have COVID-19.

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