When Swine Flu Returns in the Fall, How Bad will it Be?

Posted on | June 9, 2009 | Comments Off on When Swine Flu Returns in the Fall, How Bad will it Be?

Several years ago, when Bird Flu, viral strain H5N1, hit, I reported on it immediately. I provided several updates over the following 24 months.^1,2,3I did this not because of the numbers of people affected (many more birds died then did people) but because of the deadliness of this microbe. The bottom line for avian flu was, and at present is, that it has problems jumping from birds to humans. When it does, it is quite deadly for those humans. Luckily, human-to-human transmittance has been difficult and generally self-limiting.

Compare this with the recent Swine Flu, viral strain H1N1. It passes much more easily to and among humans but is not particularly deadly in its current form. Yet these viruses, whether Bird or Swine Flu, are always changing and always mutating. We have to understand what they are doing biologically in real time and stay one step ahead of them. And that is exactly what the CDC is doing with the current Swine Flu outbreak.⁴

Here is what we know about H1N1: the bug is pretty good at keeping itself alive by invading our nasal mucosal and spreading to other people when we sneeze. Walter Dowdle, a former chief of virology at the CDC describes H1N1 as "a real mutt" because genetically it is a mix of swine, human, and bird genes. The genetic structure of these viruses aren’t enormous like the human genome. Their entire gene library consists of eight short strands of RNA. These in turn direct the production of only 11 proteins. They invade a cell, break apart, reassemble and, depending on their chemistry, may or may not destroy the cell.⁵

The reason that H1N1 is relatively mild right now is that it lacks the genes to produce two proteins that cause havoc for humans. The first, PB1-F2, weakens and destroys cell mitochondria – the cell’s energy manufacturing site. The second protein, NS-1, attacks interferon, which is critical to an effective human immune response. Up until now, these proteins have only been found in Bird Flu. Experts say that it is unlikely that the current Swine Flu will go in this direction because it has never happened before.⁶
What is more likely is that the Swine Flu when it returns this fall, will have become resistant to the drug Tamiflu. The world has stockpiled the anti-viral Tamiflu in response to the threat of H5N1. Over the years, most seasonal viruses have quickly developed resistance to Tamiflu. If that occurs with Swine Flu, doctors and their patients in the US will likely rely on another anti-viral, Relenza. This drug is more expensive and must be taken with an inhaler. Or, older drugs like rimantidine will be used. These, too, have resistance issues of their own.^5,7,8

What we know for certain is that we have not seen the last of H1N1 Swine Flu. Thus far, it has spread fairly rapidly, but luckily without enormous human death and destruction. Thanks to concerns about the Bird Flu epidemic, we are more vigilant, have better testing, and take these viral threats very seriously- as we should.

For Health Commentary, I’m Mike Magee.

References:

1. Magee M. A Bird’s Eye View Of Bird Flu. 19 July 2006.

2. Magee M. The Threat Of Bird Flu. 24 Aug. 2005.

3. Magee M. The Battle with Infectious Disease. 16 March 2005.

4. CDC H1N1 Flu. 5 June 2009.

5. McNeil D G. How A Mild Virus May Turn Vicious. New York Times, D6. 9 June 2009.

6. Guang-Wu Chen, et al. Influenza A Virus PB1-F2 Gene in Recent Taiwanese Isolates. CDC Emerging Infectious Diseases. 10 March 2004/.

7. GSK Corporation. Flu Treatment or Prevention.

8. CDC Emergency Use Authorization Of Relenza. 1 May 2009.