Covert infections and the spread of coronavirus

Yesterday, the Prime Minister introduced strict limitations on when and how we can move about and live our lives. He said we should leave our homes only if absolutely necessary. Why is this so important?

The Scientific Journal, Nature, has published an interesting and informative article about the proportion of people with mild or no symptoms of COVID-19 who could be spreading the virus and this information highlights why limiting our movements can help to reduce the spread of coronavirus.

The first important question is how many people are contracting this virus but are experiencing few or no symptoms? It is thought that the number may be quite high because there have been many community acquired infections where the patient has no links to known COVID-19 cases and has not travelled to any area with a large outbreak.

Those people with few or no symptoms may be totally unaware they have the virus and continue to behave as normal. The article calls COVID-19 infections of this sort ‘covert infections’.

Understanding the covert infection rate is crucial if we are to slow the spread of the virus and prevent new outbreaks.

One study that the article reports on looked at 565 Japanese citizens who were all evacuated from Wuhan in February. They were regularly monitored and tested. 13 were infected but 4 (31%) had no symptoms.

The Diamond Princess cruise ship, which was quarantined with 3711 people on board, was another opportunity to study covert infections. There were 700 infections on the ship and 18% of those showed no symptoms. The authors of this study pointed out though that the average age of the people on the cruise ship was relatively high and this could have affected the data because older people tend to experience worse symptoms than younger people.

Finally, there is a suggestion that children may experience mild or no symptoms in 56% of cases.

All of this data show just how important it is to enforce extreme social distancing measures if we are to stop the virus from spreading.

Take a look at the article, it’s available for free on the Nature website.

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