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Three Reasons Why H5N1 is Not the Only Influenza Virus to Watch

You may have heard of the influenza viruses found in pigs, commonly known as ‘swine flu’. You will very likely have heard of the influenza viruses found in birds known as ‘bird flu’. But how about ‘seal flu’? Or ‘bat flu’?

At NL Associates we keep a close eye on the influenza viruses found in animals and birds in the natural world and an even closer eye on what is called the ‘animal/human interface.’  This is where influenza viruses are transmitted from animals to humans.

A Bit of Background Information – the 2009 H1N1 Influenza Pandemic

Pandemic: ‘an epidemic of infectious disease that has spread through human populations across a large region; for instance multiple continents, or even worldwide.’

In 2009 a new strain of influenza H1N1 virus was detected in humans.  This strain emerged after a series of co-infections and mutations at the animal/human interface and it began with an infected pig.

Pigs are susceptible to avian, human and swine influenza viruses. If a pig is infected with influenza viruses from different species at the same time, the creation of a new virus is possible. This process, in which genes from different viruses mix to create a new virus, is called an ‘antigenic shift’.

How it happened:

Studies of the genetic make up of the pandemic H1N1 virus have shown that it is a completely new virus, quite unlike the previous H1N1 viruses that affected humans in the 1918 pandemic and the 1977 pandemic. These genes have been found before in North American H1N2 swine influenza viruses, Eurasian H1N1 swine influenza viruses and human H3N2 seasonal influenza virus. It has appeared after a so- called “triple re-assortment in pigs”.

It seems that the virus first appeared some years ago and has been circulating in pigs in North America.

It then infected humans in Mexico in about February 2009 and was mistakenly considered to be seasonal flu.

The new virus was confirmed in US citizens on 24 April 2009 and subsequently confirmed as the cause of the influenza in Mexico.

Influenza viruses are continually evolving and mixing and the exact chain of events leading to the new pandemic strain appearing cannot be determined. Conspiracy theories abound on the internet but it is highly likely that this is a “Mother Nature” determined event. There is no evidence to suggest that this new virus was created in a laboratory; it does not like growing in eggs.

Since April 2009 the pandemic caused a reported 18,500 laboratory confirmed deaths worldwide and may, according to The Lancet, have killed many thousands more.

Flu vaccines now protect against the H1N1 virus.

Avian Influenza H5N1

Close attention is paid to the influenza H5N1 virus throughout the world. To date the virus has infected 607 people worldwide and killed 358. (Source: WHO)

Earlier this year new research was published into a strain of the H5N1 virus that had been mutated under laboratory conditions into an airborne strain. Scientists were worried that the results of the research were ‘too dangerous’ to publish for fear it might get into the wrong hands and because a bioterrorist threat. In an article about the research, published by The Guardian, John Oxford, professor of virology at Barts and the London School of Medicine and Dentistry said:

“Forget all the nonsense about bioterrorism. These papers tell us that nature is where we should focus our concern … The mutant strains that (the researchers) described are probably already out there. They must be out there. Fortunately for us, it is probably in some duck in Siberia, but were it to move close to hand by the vagaries and chances of nature, we’d be for it.

This post’s title is ‘Three Reasons Why H5N1 is Not the Only Influenza Virus to Watch’ because in recent months we have seen reports, not only of avian influenza H5N1 in the world, but of a number other types of influenza. And they are doing very interesting things:

Reason 1: Pigs

In the US this month there has been activity at the animal/human interface with a large outbreak of variant influenza H3N2v virus. This virus usually infects pigs but it can be directly transmitted to humans, as the health officials who have reported over 144 cases of human infection with the virus in the states of Indiana, Ohio and Hawaii in the last few weeks will attest.

So far there have been no cases of human-to-human transmission of this variant virus but health officials in the US are continuing to investigate the possibility that this might happen.

Reason 2: Seals

Elsewhere in the US, an influenza virus similar to one seen in waterfowl since 2002 has been detected in the bodies of 162 dead New England Harbor Seals. The seals died between September and December 2011 in an outbreak of pneumonia and the postmortem research found that the avian influenza or bird flu H3N8 virus had mutated to adapt to a mammalian host.

Calling the virus ‘bird flu’ is slightly misleading because it is not the highly pathogenic H5N1 virus prevalent in Asia that people normally think of when they read bird flu. Instead, this variant of influenza virus, H3N8v, travels in between species.

Reason 3: Bats

In February 2012 we saw a story about the discovery of influenza A virus in fruit bats in Guatemala. This is the first time that a flu virus has been identified in bats and means that the species may act as a source of flu viruses. The CDC reported on the story that the virus ‘should be studied as a potential source for human influenza.’ This virus is not believed to pose a threat to human health.

In Conclusion

So, pig flu, bird flu, seal flu and bat flu are out there. The recent human infections with variant influenza virus, seen in Indiana, Ohio and Hawaii, are a reminder that influenza viruses from pigs could potentially produce the next pandemic strain. The significance, in the case of the dead seals, is that the virus mutated while in the waterfowl and created a new variant virus capable of transmission from birds to mammals and in Guatemala, influenza has been identified in a new species this year.

The ever-changing nature of influenza viruses mean that it is vital to keep a close eye on stories like these as they emerge across the world. Avian influenza H5N1 is not the only virus that is out there and that has the potential to change and mutate.

And Finally: H2N2

In 1957 “Asian” flu appeared, caused a pandemic, went on to be seasonal flu and then disappeared in 1968 when the current H3N2 strain caused a new pandemic. The virus therefore disappeared from the wild but is kept in some laboratories; it was mistakenly sent out as a quality control strain to influenza laboratories in 2005. Anyone under 44 years old is susceptible to this previous pandemic strain.

When it comes to influenza:

It is important to be prepared.

It is vital to identify changes early.

It is important to respond appropriately.

NL Associates can provide expertise to help you in all three of these key components of emergency preparedness and response in the context of infectious disease generally and influenza specifically..

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