Flu Fatigue?
Fortunately, so far, none of the H5N1 influenza virus strains have been able to efficiently move from person to person. As media stories repeat themselves, time passes, and nothing dramatic happens, except an occasional death in a region remote from us, so it is easy to develop what some call “flu fatigue.”[1]
So what is the virus doing these days? Are we protected yet, or is it okay to tune out from the bird flu and relax our efforts to prepare?
What’s the virus doing?
It is rather obvious that the H5N1 bird flu is not going away. In the three years before 2006, this virus was reported in 15 countries. According to the conservative World Health Organization (WHO), in just the first four months of this year, H5N1 has hit an additional 30 countries and has caused major outbreaks in Turkey, Iraq, Israel, Gaza, Egypt, Afghanistan, Pakistan, Myanmar, India, Nigeria, Niger, Cameroon, and Bukina Faso. Eradication efforts had no lasting effects.
Among birds, H5N1’s march across the globe appears to be unstoppable. For a graphic in monthly time slices since January 2004, see: http://msnbc.msn.com/id/12375868 (don’t forget to hit the “Play” button). Especially in poor countries, surveillance efforts are so insufficient or nonexistent that we should not be surprised if H5N1 has reached many more countries than is officially reported.
As of April 27, 2006, the official WHO count is 205 human cases, 113 of whom have died.
Are we protected yet?
Vaccines are generally thought to be our best shot at protection against influenza.
“Safe and effective vaccines are likely to be the single most important health tool for decreasing the morbidity, mortality, and economic effects of pandemic influenza . . .” (Poland 2006)[2]
But right now, even for the seasonally recurrent influenza, the vaccine for one season is not very effective the next time around, because the prevailing flu strains change from year to year. Besides, a normal vaccine production cycle takes about six months, and it might take up to nine months to match a vaccine to a new strain and produce enough doses to protect the population. Should the H5N1 influenza virus ever cause a pandemic, no currently licensed influenza vaccine would protect us.
Influenza can move much too fast for the traditional vaccine methods to catch up. For example, three weeks after it started, the 1918 influenza had covered the continental United States. For a dynamic map, see: http://www.pbs.org/wgbh/amex/influenza/maps/index.html. Over the first six months -- the minimal time it would take to produce a traditional vaccine against a new flu strain -- the 1918 pandemic H1N1 virus had already swept over the earth in two waves and had killed tens of millions of people.[3]
Recent computer modeling suggests that a vaccine must be available within two months of the start of an epidemic or pandemic to have a beneficial effect.[4]
How is our best defense coming along?
Several efforts are coming along to improve on traditional methods, and the WHO Influenza Network has begun stockpiling a vaccine against the H5N1 influenza virus, with the intention of using it in case of a pandemic. But chances are that genetic drift, reassortment, or recombination will, over time, lead to virus variants against which the vaccine has limited or no effect.
Besides, production of enough vaccine for a fraction of the world’s population would require several billion embryonated eggs. This is a headache when you consider that the H5N1 kills poultry and is likely to reduce the yield from eggs. For many years now, such concerns have led to calls for vaccine production methods that do not depend on eggs.
Piggy-back vaccine
Vaccine research and development is progressing on a number of fronts. For example, the M2 ion channel surface marker appears to be a useful vaccine target. But to me, the most hopeful development is a cell-based rather than egg-based process. It uses a common cold virus that has been engineered to carry the H5 target and to present it to our immune system. H5 is the hemagglutinin on the surface of the H5N1 virus with which it attaches itself to host cells. The common cold carrier virus has been further engineered to cause no harm by eliminating its ability to spread in the human organism.
Two groups of researchers have successfully tested this vaccine in mice and poultry. After vaccination and infection with a live H5N1 virus, all animals survived. Control animals received a sham vaccine with the carrier virus but without the H5 antigen. All control animals died.
Potential benefits
The researchers suggest that it only takes between one and two months to prepare this kind of cell culture-based vaccine with the piggy-back virus, possibly enough to win the race with a pandemic influenza strain. The chances of successful protection are enhanced further by the finding that the piggy-back vaccine not only provided protection against the specific H5 in the vaccine, but also against other varieties of H5. Even better, this kind of vaccine not only causes the immune system to respond with a high level of antibody, but also triggers high levels of activity in infection-fighting white blood cells.
It’s still a race
The H5N1 virus may never be a serious threat to humans, but we don’t know for sure if it is only a matter of time. As the virus rapidly expands its spread in birds and repeatedly crosses the species barrier, the chances increase to an unknown degree that it will find a way to efficiently jump from person to person.
Fortunately, the outlook has brightened considerably that we will have an effective defense -- if we move fast enough. It would seem that human trials should be undertaken and unnecessary administrative and regulatory delays avoided.
My guess is that talk of flu fatigue will quickly stop when the first bird in North America is diagnosed with H5N1. If we are lucky, the enhanced attention to bird flu will boost efforts to prepare effective defenses in general and piggy-back vaccines in particular.
Earlier in April, a swan in Scotland was found to be infected with H5N1, and it is a short stretch for migratory birds from there to northern Canada. Let’s give it two months, maybe.[7]
[1] E.g., http://www.alertnet.org/thenews/newsdesk/L25263165.htm, http://news.scotsman.com/latest_international.cfm?id=627022006
[2] Poland GA.
Vaccines against avian influenza--a race against time.
N Engl J Med. 2006 Mar 30;354(13):1411-3.
[3] E.g., Taubenberger JK, Morens DM.
1918 influenza: the mother of all pandemics.
Emerg Infect Dis 2006 Jan;12(1): http://www.cdc.gov/ncidod/EID/vol12no01/05-0979.htm
[4] Ferguson NM, Cummings DA, Fraser C, Cajka JC, Cooley PC, Burke DS.
Strategies for mitigating an influenza pandemic.
Nature. 2006 Apr 26; [Epub ahead of print]
[5] Hoelscher MA, Garg S, Bangari DS, Belser JA, Lu X, Stephenson I, Bright RA, Katz JM, Mittal SK, Sambhara S.
Development of adenoviral-vector-based pandemic influenza vaccine against antigenically distinct human H5N1 strains in mice.
Lancet. 2006 Feb 11;367(9509):475-81.
[6] Gao W, Soloff AC, Lu X, Montecalvo A, Nguyen DC, Matsuoka Y, Robbins PD, Swayne DE, Donis RO, Katz JM, Barratt-Boyes SM, Gambotto A.
Protection of mice and poultry from lethal H5N1 avian influenza virus through adenovirus-based immunization.
J Virol. 2006 Feb;80(4):1959-64.
I am asking you to put info on your site about the bird flu symptoms, and about how many cases have been reported in the state of Kentucky.
Posted by: Ethel | May 03, 2006 at 06:49 PM
Please tell me about the bird flu symptoms, and if it's safe to eat KFC because i think is not cooked enough.
Posted by: Tina | June 09, 2006 at 08:58 AM