In Depth

Five reasons coronavirus may be getting less deadly

Covid-19 infection rates are rising in many countries - but death rates remain low

An increase in Covid-19 cases in the UK and many other European countries has triggered fears of a deadly second wave - but another set of statistics offers more grounds for optimism.

“It is becoming increasingly clear that people are less likely to die if they get Covid-19 now compared with earlier in the pandemic, at least in Europe,” says New Scientist.

In the UK, for example, last week’s daily average of 1,060 confirmed new cases per day was the highest since mid-June, but hospital admissions were at their lowest since early March.

“Although hospitalisations and deaths lag infections, neither indicator has shown a corresponding increase even six weeks after the number of cases began to rise,” says the Financial Times.

Here are five possible reasons for the encouraging trend:

1. Different people are catching Covid-19

In the early stages of the pandemic, the coronavirus tore through care homes, infecting vulnerable elderly people.

More recently, that pattern has changed. During June and July, “the share of people diagnosed with coronavirus aged between 18 and 64 increased from a weekly average of 24% to over 40%”, says the FT.

The newspaper suggests that the elderly are now better protected, while younger people, who are unlikely to fall seriously ill, are resuming their normal lives.

That could help explain the shift in infection fatality rates, Oxford University statistician Dr Jason Oke told New Scientist. “Yet Oke doesn’t think the change in age distribution alone is enough to account for what is happening,” the magazine reports.

Many older people are still testing positive, he explains, but more are surviving.

2. More testing

A massive increase in testing is almost certainly a factor: the UK now processes an average about 170,000 tests per day, compared with about 13,000 a day at the start of the outbreak.

“Back in March and April, we were mainly testing people who were really ill and more likely to die,” Paul Hunter, a professor of medicine at the University of East Anglia, told the FT. “Now, the programme is catching a much higher proportion of infections with mild or no symptoms.”

And that could mean the virus looks less deadly while remaining just as fatal. As medical-focused site STAT News explains, “a larger number of diagnosed cases due to more testing would decrease the reported fatality rate”.

3. Better treatments

Statistical questions aside, there is little doubt that more people are now surviving the disease.

“Doctors are getting better at assessing who should go to hospital in the first place, rather than staying at home,” Hunter tells the FT. “When patients are in hospital, clinicians are learning how to treat them more successfully.”

Ventilators are being used more sparingly, with oxygen instead given through less invasive methods. But the biggest advance has been the use of the drug dexamethasone, which has been proven to significantly reduces death rates.

4. A milder strain

Scientists are divided about whether the virus that causes Covid-19 is weaker now than it was in spring.

“Most viruses tend to become less virulent as they mutate,” says Reuters, and some scientists believe the predominant strain now spreading across Europe, known as D614G, is more contagious - but less deadly.

However, “other research disagrees”, says New Scientist. Erik Volz of Imperial College London told the magazine that “we do not see reduced risk of death due to the D614G variant”.

5. Smaller doses

“The more virus you get into your body, the more sick you are likely to get,” says Monica Gandhi, an infectious disease expert at the University of California, San Francisco.

The result of post-lockdown changes in society - with more people wearing masks, washing their hands more often, and avoiding physical contact with others - may therefore lead to milder infections.

Or as The Guardian puts it, “infectious doses of the Covid-19 virus, transmitted from one person to another, may be getting smaller thanks to social distancing”. 

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