No, you cannot get bird flu from the chicken casserole you cooked last night. Heat kills it and the virus is usually spread through the air.

No, the strain of bird flu (H5N2) found in Gonzales County, Texas (which shuttered some Houston live poultry markets for safety's sake) has not jumped to humans, and has no history of ever having crossed the species barrier.

And no, this strain is not the same strain that has plagued several countries in Asia.

The US Department of Agriculture and the national Centers for Disease Control and Prevention are doing a good job of surveillance, says Kristy Lillibridge, DVM, a former CDC disease detective and now assistant professor in epidemiology at The University of Texas School of Public Health at Houston.

"As far as how worried Americans should be as a population, our concern at this point in time [for our human health] should be relatively low," she reassures.

Then, what are the "YES" answers?

Bird Flu 101

Avian influenza or "bird flu" is a collection of contagious viral strains in the same viral family that normally infects birds. (Oddly enough, pigs have fallen victim to the virus, but not as often.)

Though any bird species is susceptible to the virus, poultry seem to be especially vulnerable and spread it quickly among the flock.

The strain names are confusing and look like serial numbers: H5N1, H5N2, H7, H9.

The two that have been in the news are H5N1 and H5N2. N2 is the one that has hit the United State twice in 20 years: once in Pennsylvania and Virginia in 1983 and in Texas this month. Neither outbreak yielded human infection.

H5N1 has been found in several Asian countries over the last few months. There is no connection whatsoever though, to the N2 strain that has infected US poultry.

Avian influenza can take one of two forms: low-potency or pathogenicity or "highly-pathogenic" (highly potent).

Low-pathogenic strains cause birds to ruffle their feathers and interfere with egg production. Highly-pathogenic strains, such as H5N1 (in Asia ) and the recently reclassified "highly-potent" H5N2 (in Texas ) cause rapid death among infected birds. Fatality rates reach near 100 percent of the flock and birds can succumb in a single day.

Since birds such as ducks and geese can fly great distances, and poultry are imported/exported across the globe, bird flu can spread quickly, if not checked.

Human Infection 101

So, what does this have to do with me, other than higher chicken prices at the check-out counter?

Plenty, if two flu strains meet and marry.

Most, but not all, of the deadly outbreaks of bird flu in Asian poultry flocks have been caused by H5N1, highly potent, and a strain that shows some talent at jumping the species barrier and infecting humans, usually fatally. Several persons fell ill and died from this strain.

Most of the victims were poultry farmers who were working closely with massive flocks of infected birds. The airborne virus entered the farmers' respiratory tracts. Human-to-human transmission, as in a farmer bringing it home to his family, has been reported in Asia, in isolated cases. No widespread human-to-human transmission exists so far.

According to the latest report from the World Health Organization (WHO), 32 cases of laboratory-confirmed cases in Viet Nam and Thailand (combined) have been reported, with 22 deaths.

Gene Swapping

The greater concern though, lies in the capricious nature and dastardly ability of the virus to mutate, swap genes with a human flu strain and create a super flu to which none of us has immunity.

In other words, if during the flu season, several poultry farmers contracted the regular Type-A human flu and also were "co-infected" with avian flu (also a Type-A form), the two flu strains could swap key genes and form a super-bug-a new strain. Brand new to our immune systems, we would not be able to fight it off. An epidemic or global (pandemic) outbreak could occur among humans and birds.

When a disease can infect both animals and humans, it is called a zoonotic disease.

Flu vaccines take months to develop. Organizations such as the CDC and the WHO would not have time to isolate, identify and manufacture an effective vaccine to stem the immediate viral tide.

It's All in the Timing

"We should consider ourselves very lucky that the avian flu in Asia did not hit during the middle of the human flu season. The outcome could have been worse," Lillibridge says.

"We already had a close call with the human Type-A Fujian outbreak," Lillibridge mentions. That was the exotic name of the strain that surfaced earlier than usual this year. Its sudden mutation fell under the radar of the ever-watchful CDC, who predicts, months in advance, which strains of flu will be virulent enough to warrant vaccine.

Next year's vaccine, currently in development, will carry protection from A-Fujian.

Genetic Drift and Shift

"Genetic drift is a term that describes why a virus can mutate so quickly," Lillibridge explains. "Certain proteins on the outside of the virus can have vulnerable surface mutation points."

When a virus is passed from person to person (or bird to bird) sequentially, the virus may begin to change. Like the passing of a rumor, each person's own style, tone, and embellishment changes the story ever so slightly. The rumor mutates, often into a super-version of the original story. That is genetic drift.

When genes from two different flu strains are residing in a single host, the two strains might start swapping genetic material. So, if a chicken farmer is already sick with Fujian flu, for instance, and becomes infected with bird flu, forming a new strain that can now live in Man and Beast, that is genetic shift.

"Genetic shift means a large mutation which could lead to a very large and serious epidemic. Species barriers can drop. The virus can jump from animal to human," Lillibridge says.

So, Can I Eat Chicken and Eggs or Not?

Yes. Grocery-bought chicken and eggs are safe once cooked. (NO uncooked or undercooked chicken or egg is considered safe for other unsavory reasons, such as salmonella.)

What About Handling Raw Chicken?

Even if the chicken you bought was infected with H5N2, risk of illness is quite rare. Since avian flu is transmitted through the air, like most respiratory illnesses, the handling of raw poultry would not necessarily "spew" the virus into the air. The major threat is to poultry workers who handle live, breathing chickens and droppings. Even then, the US strain has not been known to sicken humans.

However, handling raw poultry (and beef and fish) can make you sick with a variety of other pathogens if your hands find their way to your mouth before they are washed. Cross-contamination with raw meats of any kind can happen if you use the same unwashed knife, for instance, to cut up your salad.

As always, the best defense is a simple offense: wash your hands, keep them clean and get the flu vaccine next autumn.

Last Updated: 3-01-2004