Andes virus

"On reading," by Simon Wain-Hobson, is a weekly discussion of scientific papers and news articles around gain of function research in virology.

Since January 2024, Dr. Wain-Hobson has written weekly essays for Biosafety Now discussing risky research in virology. You can read his entire series here.

Umbrella pines, south of France

On reading Andes virus genome mutations that are likely associated with animal model attenuation and human person-to-person transmission by Carla Bellome and colleagues, mSphere 2023; 8:e0001823

The next pandemic: hantavirus?

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The hantaviruses represent a group of animal viruses that are little known to the public. The can spillover to humans and cause kidney, cardiac and pulmonary disease. While transmitted by rodents, fortunately they are rarely transmitted between humans. As such they are yet another example of spillovers or dead-end infections. There are around 200,000 such hantavirus infections worldwide per year. Patient mortality varies from 5 to 40% depending on the virus.

In the Four Corners region of the US there were 849 cases between 1993-2021 of Sin Nombre hantaviral pulmonary syndrome. Sin Nombre is one of a large group of New World hantaviruses half of which can spill over to humans. It would seem that this hantavirus was responsible for the recent death of Betsy Arakawa, Gene Hackman’s wife.

Andes virus in another hantavirus first described in 1995 during an outbreak in Patagonia. Since then, it has caused more than 1200 cases in Argentina. It’s also found in Chile hence the name. It causes severe pulmonary disease requiring intensive care treatment (84%) with mortality around 21%.

Andes virus is unique among hantaviruses because it can be transmitted from person to person. Transmission is aided and abetted by large social gatherings or extensive networks.

The strains of Andes virus analyzed in the present study were isolated from human-to-human transmission and contained three protein changing mutations compared to the rodent virus.

So?

• Andes virus is a step beyond H5N1 bird flu virus in that it can establish short human-to-human chains of transmission. Andes virus shows that there is more to becoming a pandemic than human-to-human transmission. Epidemiologists will say that transmission to more than one person is required for an epidemic or pandemic to take off. As hantaviruses are members of the RNA virus group, they are rapid mutation machines so it could well acquire what it is presently lacking and go big time. No researcher has the foggiest idea if Andes virus will or when.

• Andes virus is on the public health map. The Global Alliance for Vaccines and Immunization has a finger on it, while it’s on the UK’s list of ‘high consequence diseases’ although it is far less commented on than H5N1 bird flu. This is probably because humans have experienced flu pandemics, whereas a hantavirus pandemic has never been recorded. The WHO has a weekly update of animal flu spillovers. The total number H5N1 bird flu infections in humans between 2003-2025 is 971 with 467 deaths.

Yet Argentina alone has seen more than 1200 cases of human Andes virus infection.

• Unlike the Fouchier and Kawaoka’s engineered H5N1 flu viruses, these Andes virus strains are natural. Hence the information about the mutations conferring adaptation and transmission between humans is useful to public health officials and will help understand Andes virus genomes as they are discovered. However, knowing viruses there are multiple ways of doing the same thing in virology epitomized by the Paul Simon song, Fifty ways to leave your lover. This means that the mutations described in this paper and elsewhere are not the last word on the matter.

• Worldwide surveillance picked up these viruses. The same can be said for Nipah, an RNA virus from a different group. Even a dead-end bird flu virus infection in a single person is known. And while surveillance systems are always playing catch up with rapidly evolving viruses, in the age of rapid and cheap genomics, this is doable. Obviously, it needs financial support.

Certainly, more sampling is better and will provide more resolution and clarity. And when coupled to lab and animal work we’ll have a reasonable idea of what individual strains are capable of. There will always be problems knowing what mutations Andes virus genomes need to start a pandemic, if that is indeed possible. But as we have learnt from the dangerous GOF research controversy on H5N1 bird flu viruses, engineering them in the lab isn’t going to answer these questions.

What is the state of play on hantavirus vaccines and drugs? A 2024 study of a mRNA vaccine to Andes virus (ANDV) showed the development of a protective vaccine against ANDV… in rodents. Also in 2024 a clinical trail demonstrated that an ANDV DNA vaccine was safe and induced a robust, durable immune response.

As for drugs, a promising candidate that could be used in the future for hantavirus treatment is favipiravir. It has been approved in 2014 in Japan to treat pandemic influenza infections and is reported to inhibit broad-spectrum RNA viruses, including Andes virus.

The numbers game shows Andes virus to be just as deadly as H5N1 flu virus yet this is not the public’s perception who knows little of Andes virus. This is understandable as we have had five flu pandemics in a century. That said, nobody has predicted any pandemic ever, apart from saying one day soon which doesn’t count.

The bird flu drums calling for GOF research on H5N1 from cows (Some housekeeping) need to be contrasted with the findings for Andes virus.

Conclusion

Cut the drum beating which is just another form of lobbying. The noise could distract from picking up the sounds of other viruses.

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Aside

A plea to the Argentinian and Chilean governments not to cut back on surveillance work on Andes virus.

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Simon Wain-Hobson is an emeritus professor at the Institute Pasteur, Paris, from which he retired in 2021. He and his colleagues were the first to sequence the genome of HIV, and Wain-Hobson has published more than 230 papers on virology and cancer.