Where are we on H5N1?

Effect Measure editors point the answer to a paper they tagged “The best summary of H5N1 to date”. It’s a commentary by Robert Webster and Elena Govorkova that appeared in the New England Journal of Medicine (NEJM Vol 355;Nov23:2174-2177).

Every sentence between these two (opening and closing) paragraphs is a gem and the whole summarizes the history and essential points in the rapidly moving science of H5N1.

I went through the review/commentary paper and got a few gems myself -

1. The two H5N1 clades sufficiently differ in their antigenic structure, and animal studies indicate that vaccines may only be effective against the clade it was derived from. Since we don’t know the strain that a pandemic virus might take, there is no guarantee that vaccine “priming with one clade may be beneficial”.

2. The majority of H5N1 clade 1 viruses (e.g., A/Vietnam/1203/2004) are resistant to the adamantanes (amantadine and rimantadine), but the majority of clade 2 viruses (e.g., A/Indonesia/5/2005) are sensitive. Furthermore, the window of effective treatment is limited to only 1-2 days after initial infection.

3. The most effective strategy so far is agressive vaccination of all poultry with an inactivated, oil-emulsion vaccine implemented by Vietnam. Other strategies such as vaccinating uninfected poultry, or eradicating H5N1 at the source have failed, thus far.

4. Similar to seasonal flu, the H5N1 virus is more transmissible among chickens, and to humans. during cooler months. Since the winter season is about to begin in the northern hemisphere, the spread to the Americas of H5N1 bears watching.

Tags: New England Journal of Medicine, Effect Measure, H5N1, transmissibility, amantadine, rimantadine

[Thanks, Hsien!}