H7N9 virus: Is it really novel – or just new?

Image copyright Getty Images Image caption The virus will be tried on a large number of animals

The last time it’s been trialled in humans was in 1953, so the H7N9 bird flu strain known as COVID-19 can be considered a “black swan” in the epidemic warning game.

World Health Organisation officials are meeting now to consider whether to allow the new, potentially pandemic-causing virus to enter humans.

The WHO already declares diseases as novel when there is a new H5N1 strain of bird flu and a new H1N1 strain of swine flu.

Scientists fear COVID-19 is a better mutation than any of the groupings of H5N1 and H1N1 flu strains that are known to have caused epidemics in recent years.

But are COVID-19 and similar viruses new enough to be considered novel?

Chart of recent threat types

A “non-probability” test based on a statistical model that considers the number of H5N1 viruses and H1N1 viruses detected over the past decade points to yes.

But if this particular strain is too new to be classified as novel, or if it is part of another H5N1 cluster, experts stress that the risk of COVID-19 spreading to humans remains very small.

If a virus passes out of a bird house (a healthy H5N1 virus will mutate into a COVID-19 variant before doing so) but does not become a pandemic virus, scientists say it is unlikely to be the true threat it might be perceived to be in other situations.

Indeed, many experts say COVID-19 is a significant test because it is the first H5N1 virus described since the 1918 Spanish flu outbreak, which is now believed to have killed as many as 200 million people worldwide.

Image copyright Getty Images Image caption Experts say COVID-19 is also a test of whether natural pathogens need to be labelled as “new” so we can plan better

No similar H5N1 or H1N1 flu cases had been noted to date in people, although the fear now is that in small numbers of dead birds COVID-19 could easily mutate into H5N1 or H1N1 flu strains.

This raises fears of a potentially lethal “super-strain” of H5N1 or H1N1 flu that would make the 1918 Spanish flu outbreak look like a mild mild on-set.

However, scientists who attended the WHO meeting on COVID-19 said this hypothetical is probably a long way off.

Dr Guillermo del Cueto of the University of Basel in Switzerland said that laboratory tests so far had shown COVID-19 does not have the characteristic genetic changes seen in H5N1 flu and most of the H1N1 viruses.

“In the foreseeable future, the risk is small,” he said.

Image copyright Getty Images Image caption H5N1 has caused the most known epidemics in recent years

Asked if the risk that COVID-19 could evolve into an influenza strain capable of causing a pandemic is low, one of WHO’s experts on pandemic flu Dr Kennet Snorriwa, said: “The short answer is that it is low, but there is a high level of scientific uncertainty.”

Critics also warn that the worrying novelty of COVID-19 has implications for the world’s preparedness for an outbreak of any potentially pandemic H5N1 or H1N1 flu virus.

The virus is usually reported as a “not-yet” pandemic. Yet it is being trialled on up to 500 animals, such as ferrets, at least some of whom have apparently died.

The test-going is now set to end at the end of October.

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