Tuesday, March 27, 2007

Are We Seeing A Change In The H5N1 Virus?

 

# 596

 

Well, if you are a follower of Dr. Henry Niman, of Recombinomics fame, then you may have reason to believe so. Over the past couple of days, Dr. Niman, has posted a couple of commentaries on just that possibility.

 

In fairness to my readers who may not be familiar with Dr. Niman’s work, he is a bit of a lightning rod. His theories of recombination are not widely accepted by the scientific community.  There are some that hail him as a genius, while others regard him with considerably less awe. His theories are controversial. He has, however, helped direct the spotlight on the H5N1 virus in ways that few others have managed over the past few years.

 

Not being a virologist, I can only skim these commentaries and pick up the gist of them; I have no idea if his assumptions are correct.   I'm presenting this information simply because it has been the talk of the flu forums the past couple of days.  Caveat Lector.

 

Dr. Niman's  latest two commentaries on the subject are here and here.

 

For those of you similarly challenged by the arcane art of reading genetic sequences, the short take on this is: a change in the HA (Hemagglutinin) segment of the virus has been detected in the latest sequences out of Egypt. These cases have reportedly demonstrated milder symptoms than previous cases.

 

In fact, cases reported between October of last year and mid-February of this year out of Egypt had a dismal survival rate, with 7 deaths recorded. Since February 16th, no new deaths have occurred, although 9 new cases have been detected. 

 

Admittedly, a number of these cases are still hospitalized, and their ultimate outcome is unknown. But media reports suggest that these patients are stable, and are responding to treatment.

 

Assuming that a change has occurred, is this good news or is it bad news?

 

At first glance, given our concern over the high CFR (case fatality rate) of the virus, any reduction in the lethality would seem to be a welcome change. After all, we’d fare far better in a pandemic with a virus that killed only 2% of its victims than one that kills 60%.

 

There is even the possibility that a mild form of H5N1, should it become easily transmissible, could effectively confer a relatively painless herd immunity to the deadlier forms of the virus.

 

Something to hope for, anyway.

 

But there is a darker side to this equation, and it is one we need to be aware of before we don party hats and declare the threat to be over.

 

The H5N1 virus has, in the past, demonstrated a lower fatality rate, only to grow more lethal over time. It is an evolving organism, picking up mutations as it spreads, and what happens in one (or a handful) of hosts in one country has little or nothing to do with how it is evolving elsewhere in the world.

 

In Indonesia, the death rate has only been going up in recent months. At least, that’s true if they are detecting all of the cases. Again, something we can’t know for sure.

 

The fear with human infections is that as the virus inhabits a human host, it could pick up favorable mutations for infecting more humans. Should a chain of infections occur, there is the fear that each link in the chain will further enhance the virus’s ability to infect, and kill, people.

 

Essentially adapting the virus from a primarily avian pathogen to a human disease.

 

A milder form of the virus, one that doesn’t present with a devastating pneumonia, is more likely to go untreated and unreported, and the infected host is more likely to remain in contact with other people, and spread the virus.

 

Put simply, the more people infected, even with a milder version, the better the odds are that the virus will adapt to humans, and a pandemic strain will evolve.

 

During the 1918 Spanish flu, a mild version of the virus apparently swept around the world during the spring, and few people even realized that a pandemic was brewing. When it returned the following October, in a far more lethal form, it killed tens of millions of people.

 

There are now over 2000 variants of the H5N1 virus on file, most involving minor, and poorly understood changes in their genetic sequences. Undoubtedly, there are many more we simply haven’t sequenced. Each has the potential to make the leap to a pandemic strain.

 

If a mild form of the virus were to acquire easy transmissibility, say in Egypt, and then spread to an area where the deadlier form of the virus is entrenched, they could (theoretically) combine into a hybrid; an easily transmitted, deadly influenza.

 

Of course, much of this is speculative.

 

We have too few cases thus far in Egypt to draw any real conclusions. We could be seeing a temporary blip, an aberration, and the virus could revert to its deadlier incarnation. Or this `milder virus’ (if it exists) may never become easily spread. And even if it does spread, there is no way to know if it would combine with another virus.

 

Whether any of this has any validity, or is good or bad news in the long run, will have to wait until we know more.