It's that time of year again--avian flu panic season. As the weather turns colder in the northern hemisphere and the flu starts making its annual rounds, the media and their anointed health experts are chirping and squawking once again about how we could be blindsided by a pandemic that some have estimated could kill a billion persons worldwide. New books like The Coming Avian Flu Pandemic join last year's The Monster at Our Door: The Global Threat of Avian Flu.
A year ago in these pages I clucked at all this, laying out the evidence that the alarmists were wrong, that avian influenza type H5N1 would not become readily transmissible from human to human and therefore not become pandemic--meaning a global epidemic. (See "Fuss and Feathers: Pandemic Panic over the Avian Flu," November 21, 2005.) Some of the arguments I made have quietly caught on. For instance, health officials, including National Institute of Allergy and Infectious Diseases director Dr. Anthony Fauci, no longer talk about an "overdue pandemic" (because there is no pattern to when pandemics occur; they are never "due" or "overdue"). But the damage has been done. A Harvard School of Public Health survey of adults who have children revealed that 44 percent think it "likely" or "somewhat likely" there will be "cases of bird flu among humans in the U.S. during the next 12 months." Less than a fifth of respondents considered it "not at all" likely.
Not coincidentally, an avian flu bureaucracy has become entrenched. Like all bureaucracies, it will fight to survive and thrive, egging on governments to provide ever more money. The alarmingly titled 2006 Guide to Surviving Bird Flu is published by no less than the Department of Health and Human Services. Never mind that no one in this country has yet even contracted bird flu. Congress last year allocated $3.8 billion to prevent the ballyhooed catastrophe (Bush requested almost twice that amount). The latest "scary news," promulgated in the November 23 issue of the New England Journal of Medicine by über-alarmist Robert Webster of St. Jude Memorial Children's Hospital, is that human cases of H5N1 contracted from birds are continuing to increase. Indeed, confirmed cases for 2006 are running ahead of those for last year. But the difference is slight; 97 worldwide for all of last year versus 111 through the end of November 2006. This difference could be entirely explained by better surveillance. Moreover, the real concern is not sporadic bird-to-human transmission, but human-to-human transmission. Far more people die of tuberculosis in an hour than all those known to have died from H5N1.
So it's time to revisit the allegations and show that as small as the risk was a year ago, it's nevertheless dropped considerably since.
Mutation and Reassortment
A flu pandemic can come about in two ways. One way is for the virus to randomly mutate to become easily transmissible between humans. "Randomly" is the key word here. There are no evolutionary pressures to make H5N1 adapt better to humans. Given enough time, H5N1 might mutate so that it could under the right conditions become pandemic. But that could take millions of years, during which time it would be more likely to mutate itself out of existence. H5N1 was first identified in Scottish chickens in 1959. It has been flying around the globe for close to half a century and hasn't done a number on us yet. There's absolutely no reason to think it will pick this year or next to do so.
Another scenario is that somebody with human flu could contract avian flu at the same time and the two flus could "reassort" into hybrid avian-human flu. The last two flu epidemics in the 20th century--1957-58 and 1968-69--were caused by such hybrids. We can help reduce this possibility by vaccinating as many people as possible (especially Southeast Asian poultry farmers) against human flu, thus reducing the potential number of "mixing vessels." Programs underway to keep farmers away from poultry droppings and spittle (birds don't sneeze or cough) will also help.
Ferreting Out the Truth
A fascinating study in the August 8, 2006, issue of Proceedings of the National Academy of Sciences would seem to indicate we're already pretty safe from a human-avian hybrid. Researchers from the U.S. Centers for Disease Control and Prevention conducted three separate studies with ferrets, which are among the few animals known to suffer from and transmit human flu. The ferrets were infected with several H5N1 strains in addition to a common human influenza virus (H3N2) that circulates almost every year. The infected animals were then either placed in the same cage with uninfected ferrets to test transmissibility by close contact or in adjacent cages with perforated walls to test spread of the virus from respiratory droplets.