Alert without alarm: what to do with the swine virus with 'pandemic potential' detected in China

By Ian M. Mackay, The University of Queensland

Researchers have found a new strain of influenza virus with "pandemic potential" in China. It is a virus that can be spread from pigs to humans, and which has generated quite a few alarming headlines.

That the virus has been detected so soon is excellent news, since activating the alert situation quickly allows virologists to take action and develop new specific tests for this specific influenza virus.

But it is important that we understand that until now there is no evidence that this virus can be transmitted from human to human. And although antibody tests have shown that some Chinese pig farm workers have had it in the past, there is no evidence at the moment that this virus is particularly deadly.

What we know so far

China has a fantastic influenza surveillance system in place in all its provinces. They track the appearance of flu outbreaks that originate from birds, humans, or pigs. And they do so because, as the scientists in the article affirm, "the systematic surveillance of influenza viruses in pigs is key both to issue an early warning and to be prepared for a potential pandemic."

Between 2011 and 2018, in their surveillance of influenza viruses from pigs, the researchers found what they called "a recently emerged genotype 4 (G4) and reclassified as H1N1 virus, similar to those from Eurasian birds (EA)". In that article they called the G4 EA H1N1 virus. They argued that it had been spreading very slowly since 2013, and that it became the key component of the H1N1 virus of porcine origin that was detected in China in 2018.

In Spanish: what they discovered was a new type of flu that was a mixture of our human H1N1 flu and another of avian origin.

What is interesting is that the antibody tests have shown that the workers of the pig farms in the affected areas were infected. Among the workers tested, around 10% (35 people out of 338) showed signs of having contracted the new G4 EA H1N1 virus in the past. People ages 18 to 35 seemed more likely to have had it.

Most notable, however, was that a small percentage of the total blood samples collected also tested positive for antibodies; samples that came from people who, in principle, had little contact with the pigs. That is, these people had also had the virus in the past.

It is highly relevant that until now researchers have found no evidence to suggest that transmission of the virus between humans is possible. They have discovered "infectious efficiency and aerosol transmission in ferrets", which means that there is evidence that the new virus can be transmitted through airborne droplets from ferret to ferret (these are animals that are We often use them as substitutes for humans in studies of influenza viruses.) Ferrets infected with the G4 virus became ill, lost weight, and suffered lung damage, as did other specimens infected with a seasonal strain of the human influenza H1N1 virus.

They also discovered that the virus can infect cells in human airways. Most people do not yet have antibodies to G4 viruses, which means that most human immune systems lack the tools to fight the disease should they have to deal with such a virus.

Bottom line: This virus has been circulating for years, we know it can jump from pigs to humans, and it meets all the requirements to become one of those infectious diseases that researchers call PPP (potentially pandemic pathogen).

If a human is infected, is it serious?

We don't have too much data to work with yet, but people who have had those infections in the past probably don't even remember they did. The new article on the matter doesn't offer too much detail, but none of the people from whom the samples came died of the virus.

There is no indication that this new virus has had a major impact or a major expansion in the regions of China where it has been detected. China has excellent virus surveillance systems and we should not be afraid at this time.

The World Health Organization has stated that it is closely following developments, and that this "highlights that we cannot lower our guard against the flu."

¿What will happen now?

People working in my field (infectious disease research) are alert, but not alarmed. New strains of flu emerge from time to time and we need to be prepared to respond to them. We have to pay the utmost attention to any possible signs of human-to-human transmission.

As far as I know, the specific tests we use for human influenza will not be able to identify this new G4 EA H1N1 virus, so we should develop new tests and have them ready soon. However, our standard influenza A screening tests should work.

In other words: we can know if someone has the so-called "influenza A" (a type of influenza virus that we normally detect in seasonal influenza). But it is a very general term that covers many types of flu strains. We do not yet have a specific test to detect this specific strain discovered in China, but we will be able to develop one quickly.

Being prepared in the laboratory is key in case we detect unusual spikes in the flu. This preparation underscores the importance of pandemic planning, current virus surveillance systems, and the implementation of comprehensive health policies.

And, as with all flu, our best defenses are to wash our hands thoroughly and maintain social distance in case others, or ourselves, have the slightest symptom.

Ian M. Mackay, Adjunct assistant professor, The University of Queensland

This article was originally published in The Conversation. Read the original.

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