Seasonal Viral Epidemics & COVID-19

Jon Cohen of the Journal Science has briefly reviewed a subject that we will all be interested in before much longer as the coronavirus COVID-19 spreads throughout the world, seasonal epidemics. This is certainly not the first time that a new coronavirus has appeared, apparently from nowhere and spread, killing people along the way. Over many years those viruses have been and gone, some with more publicity than others. Why?

Many of us might remember the SARS (Severe Acute Respiratory Syndrome) outbreak in 2002/3 which arrived in Hong Kong, briefly shocked us and caused 774 deaths.

Since then we have had MERS (Middle East respiratory syndrome) which appeared in 2012 and still occasionally pops up but spreads very slowly.

Where did they go? We didn’t develop an effective vaccine, we didn’t use a new treatment, they just disappeared. Why?

Cohen looks at these and many more disease outbreaks and the seasons they first appeared and when they disappeared – there are clear correlations.

Clearly many epidemics follow a seasonal pattern. Enveloped viruses like SARS and Influenza seem to favour the winter (SARS appeared in November 2002) but disappear during the summer months for reasons we don’t fully understand. There have been many experiments on possible causes including air humidity and sudden changes in air humidity but evidence remains inconclusive. Perhaps part of the reason is that we naturally use greater self-distance in the warmer weather? Perhaps higher temperatures or sunshine contribute? More detail here.

We can’t really conclude that SARS was defeated by summertime changes in climate as in the case of SARS there were aggressive attempts to contain it much as we are seeing now for COVID-19, so we might at least partly thank those activities for defeating SARS 2003.

COVID-19 is 80% identical to SARS  so there might be a suggestion that it too will fade as summer progresses but at the moment we cannot rely on that hope as we know too little about this new virus. Of four other coronaviruses that we know about three do disappear in the summer, but one doesn’t. COVID-19 is a lot less lethal but a much better spreader compared with SARS, and it seems to be spreading regardless of climate, so currently suggests that it will not be affected by differences in humidity or temperature.

As with many aspects of COVID-19, we must try to keep it under control as far as that is possible and wait until it shows us more of its behaviour.

For the full article click here.

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