Monday, December 13, 2004

Bird flu: "Holding our breath"

I would like to stand back and take a sober look at the current situation regarding "bird flu."

Here's what we don't know at this moment:
  • if H5N1 influenza A ("bird flu") will make the transition from rare and sporadic bird-to-human transmissibility to full-fledged human-to-human transmissibilty;

  • if it does, whether it will retain the virulence seen in the human cases thus far;

  • if these things happen, whether an avian influenza pandemic will be this year, next year or never.
Here's what we do know:
  • all the ingredients are in the soup;

  • if it happens we aren't ready.
The ingredients:

(a) A bird influenza virus, designated H5N1 for its surface antigens and to which the human population has no effective immunity, crossed over to humans in Hong Kong in 1997. There were 18 cases, of whom 6 died. Since January of this year (2004) there have been 44 cases in Viet Nam and Thailand, of whom 32 have died, an unusually high case fatality rate;

(b) The virus has changed since 1997, persisting longer in wildlife and the environment and has been found in new hosts, including mammals (large and small cats and mice, the latter in the laboratory) and wild and domesticated ducks, wild herons, ostriches and other birds, including, of course, chickens. Ducks excrete large amounts of the virus but appear unharmed by it. The 2004 strain is not identical to the 1997 strain. H5N1 seems to mutate with facility and speed;

(c) Southern China and Southeast Asia where H5N1 is now endemic is like a huge incubator for influenza viruses. Here people and their livestock, including chickens, ducks and pigs, live in close proximity. Pigs can be infected with human strains of influenza A virus. If humans or pigs are simultaneously infected with H5N1 there is the possibility of the kind of genetic reassortment that could produce an H5N1 adapted to human transmissibility. While most such reassortments will not be problematic,those that can use humans as hosts will be selected for in an evolutionary sense. Random genetic changes in the virus could produce the same result, without co-infection. For a virus, a host of any kind is merely a way to make another virus;

(d) We live in an era of unprecedented population mobility. Commercial air travel can deliver infected individuals around the globe within the incubation period of influenza A. At the same time many urban areas are disastrously overcrowded, and civil and national wars are resulting in population displacements that are difficult to impossible to control (e.g., Darfur, Congo):
'No man is an island,' said John Oxford, professor of virology at Queen Mary Westfield school of medicine, London. 'It doesn't matter where it starts -it will be on our doorstep within 12 hours. You can't argue that it isn't our problem.' (quoted in The Guardian Online).
Containment will be impossible.

(e) If the human species does not suffer a major population crash under conditions of overpopulation, overcrowding and a deteriorating environment, it will be unlike almost any other species known to natural history. Unlike other species, however, we have non-biological tools like technology and culture to help us. Will we use them properly?

We aren't ready:

If H5N1 pokes its head above water in the human population, we will not be able to stop it with our current medical measures of immunization and prophylactic medication.

Two large pharmaceutical companies are about to begin clinical trials of an H5N1 vaccine (see post), but its effectiveness, timing and access for most of the world's population are unknown at this time. There are few antiviral drugs that seem effective. Oseltamivir (trade name Tamiflu) has been approved by the US FDA for preventive use and may have some effectiveness against H5N1. Older antivirals that have generic versions like amantadine appear not to work for avian influenza in humans.

The use of vaccine and antivirals might buy some valuable time while civil societies prepare and then try to cope with the consequences of a serious influenza epidemic. Neither will prevent a pandemic hitting with considerable force. But stretching out the epidemic curve can be important.

If and when that happens, most authorities feel the US is less well prepared than other countries. An excellent in-depth story by The Observer/Guardian Online (same link as above) compares the US to the UK:
The UK ... has been in negotiations with Roche [manufacturer of Tamiflu] for months. Even if Britain buys enough doses only to cover between 10 to 20 per cent of its population, that bill will still come to millions of pounds...

Britain also has a strong network of public health groups and is well placed to implement the plans that it is currently working on for dealing with the emergence of a flu pandemic.

By contrast, the United States looks ill-prepared and has bought antivirals to treat only one million of its 300 million citizens. 'We're all holding our breath,' said Julie Gerberding, head of the Centres for Disease Control and Prevention. Australia and the Netherlands have stockpiles that meet the demands of around one-third of their populations.
"Holding our breath" might work to prevent inhaling some influenza virus from your neighbor's sneeze, but our nation can't hold its breath. As a strategy it doesn't cut it. Our federal and state health establishment still has not gotten its act together. In a future post I will explore what needs to be done and suggest ways to get it done in the absence of effective public health leadership.