Bird Flu: Don't Fly Into A Panic

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Bird flu: Don't fly into a panic

Whether the H5N1 virus will "make the jump" and spread among humans is uncertain, but here are some tips to protect yourself.

It's a confusing world. While the H5N1 bird flu virus spread across Europe and Congress set aside billions for flu research and prevention, skeptical voices emerged.

One researcher noted that no H5 subtype (the H stands for hemagglutinin, the surface protein that a flu virus uses to bind to host cells) has ever caused a flu pandemic. Others said that even if H5N1 did mutate so that it could spread easily from person to person - a prerequisite for any major epidemic - the resulting virus would be weak and unlikely to cause serious illness.

In March 2006, researchers reported that the receptors H5N1 needs to replicate are found only in the lower respiratory tract; usually viruses that cause respiratory illness spread easily only when they inhabit the upper respiratory tract. The implication was that H5N1 would have to undergo some major mutations before it became a serious threat to human health. On the other hand, the H5N1 virus has already jumped from birds to pigs and cats, as well as infecting some people, suggesting it might have an unusual capacity to develop into a human flu.

So should we be afraid - or cynical? Ideally, neither. At the risk of stating the obvious, no one knows for certain whether H5N1 is going to explode or fizzle, or whether a different flu virus with greater pandemic potential might be "cooking" out there right now.

Public health officials must plan for the worst. As individuals, we can steer a moderate course and take a few precautions. Besides, a lot of the recommendations for protecting ourselves against bird flu make good sense for reasons apart from a flu pandemic that may or may not occur. Here are eight items on our bird flu to-do list.

1. Get a regular flu shot this fall

For all the fear it has aroused, H5N1 in its current form has killed about 100 people worldwide - and it has been in circulation, on and off, since 1996. Regular seasonal flu, by contrast, kills thousands of Americans, most of them elderly, every winter. So if you are concerned about flu, getting a regular seasonal flu shot is the place to start.

By getting a flu shot you're also doing your part to keep H5N1 mainly confined to birds because you are reducing the chances of a co-infection that would allow the bird flu to merge with a flu virus that is already transmissible among people.

But regular flu shots aren't going to offer full protection against H5N1 - or, to be more precise, H5N1 that has mutated so it spreads among humans. Researchers are working on such a vaccine. They reported positive results in the New England Journal of Medicine in March 2006, but there was a hitch: The vaccine was effective (as measured by the antibodies it generated) only at 12 times the normal dose for a flu vaccine, so a lot would be needed. And it was produced the slow, old-fashioned way, in fertilized chicken eggs. If this were the only vaccine available in a pandemic, demand would quickly outrun supply.

Experts are looking for adjuvants, substances that enhance the immune response of a vaccine and therefore allow the supply to be "stretched" into smaller doses.

Genetically engineered vaccines are another possibility. Scientists hope to be able to slip chunks of harmless genetic material from H5N1 - or whatever virus happens to pose the clear and present danger - into material that has been gleaned from, say, a benign cold virus. The idea is to create an artificial virus that tricks the immune system into producing antibodies against the flu. Some vaccines are already made this way but for flu, it's still the stuff research projects are made of.

2. Don't count on the antivirals to be the silver bullet.

The FDA has approved zanamivir (Relenza) and oseltamivir (Tamiflu) for both treatment and prevention of flu. If you take these drugs (Relenza is a powder you inhale through your nose; Tamiflu is a pill) within two days of coming down with the flu, they're supposed to reduce the length of the illness by about a day. More important, there's some evidence that taking them will reduce your chance of catching the flu in the first place.

The World Health Organization (WHO) and other groups have encouraged use of antivirals, in part so that doctors and patients will be familiar with them if a pandemic does occur. At the same time, the FDA has had to set up safeguards against hoarding.

Anyone banking on antivirals should be worried by an extensive review of 51 studies published in the Jan. 28, 2006, Lancet. This "study of the studies" casts serious doubt on the preventive value of zanamivir and oseltamivir, especially in the midst of a pandemic, when sick people may be carrying a higher viral load - more of the virus - than during a normal flu infection.

In fact, say the reviewers, using zanamivir and oseltamivir for prevention might create resistant strains that would make the drugs useless for treatment. They add that there is "no credible evidence" that zanamivir and oseltamivir are effective against flu originating in birds. In a few of the cases of H5N1 infection that have killed people, the virus has quickly developed resistance to oseltamivir.

Yet their bottom line doesn't differ that much from what others are saying: These drugs have their place (symptom relief, possibly some reduction in transmission), but relying on them too much could hamper the development of other public health measures.

3. They were right: Wash your hands!

Parents and minders of childhood hygiene everywhere can savor this "I told you so." Our hands are filthy with germs - mainly bacteria, but also viruses, including flu viruses. So one of the best ways to protect yourself and others against flu - pandemic or otherwise - is to wash your hands regularly. How often you wash them matters more than what you wash them with. Plain old soap and water are fine for most purposes.

But many hospitals are switching to alcohol-based hand rubs, which are easier on the skin and kill more bacteria and viruses. Here at Harvard Medical School, they've put hand rub dispensers near the elevators at the Countway Medical Library. Having dispensers in public places makes hand hygiene convenient and drives home the message that it needs to be part of our daily routines. We'd like to see more of them around.

By the way, studies in several settings have shown that there is a big gender difference in hand hygiene. Gentlemen, it's time to clean up your act.

4. Don't shake hands.

Even if you always practice good hand hygiene, others may not. WHO recommends greeting people by bumping elbows instead of shaking hands. If this "bird flu bump" seems odd (it does to us!), you might try a nod or a Japanese-style bow. If you continue to shake hands - most of us will, unless there is a raging pandemic - step up the handwashing. Bird flu pandemic or not, clean hands are a way to keep from getting sick.

5. Cook chicken till the pink is gone.

As we went to press, the H5N1 virus hadn't spread to poultry in North America. Odds are that it will. Although most flu viruses that infect birds stay in the respiratory and gastrointestinal tracts, strains like H5N1 may spread to the rest of the bird, including the meat. Raw, blood-based chicken dishes may have caused a few human infections, according to WHO. Still, bird flu isn't considered a food-borne illness. And there's no evidence that anyone has been infected by eating even contaminated chicken, as long as it is cooked properly. That means the center of the piece of chicken should be piping hot (about 180° F) and all the pink should be gone.

This isn't new advice. The same precautions are necessary to prevent salmonella infections.

As far as eggs are concerned, infected hens eventually stop laying, but eggs produced early in the infection may contain viruses in the white and yolk or on the surface of the shell. Again, cooking is the best defense. If you want to stay on the safe side, don't eat runny yolks.

When bird flu was discovered in Britain in April 2006, food officials there told restaurants to stop making dishes with ingredients that include raw eggs, such as mayonnaise and mousses. They said store-bought mayonnaise was okay because it's made with pasteurized eggs.

6. Stay home if you're feeling ill.

Some of us like to soldier on. But if you stay home when you're sick, you'll not only be sparing co-workers, family, and friends some misery but also doing your part to stop the spread of an illness that could be flu, be it a garden-variety virus or the pandemic "big one." Keeping sick children home from school may be even more important: Schools are incubators for a menagerie of respiratory infections, including flu. In fact, one way to break the back of an epidemic is to keep kids home from school.

7. Stay away from birds and their droppings.

Wild birds are the perfect carriers for most flu viruses. They get infected without getting sick, and they shed the virus in their feces and feathers over long periods of time. Migratory birds seem to have brought H5N1 from Asia to Europe and Africa.

Health officials are advising the public not to touch dead or injured birds. If you must handle birds, wear gloves. Bird droppings can harbor live virus, so watch where you tread.

Yet the chance of catching the flu from a brief encounter with a bird or its droppings is small. At least so far, direct transmission from birds to people has been rare. Most of the people who have contracted H5N1 from chickens did so only after constant, intense exposure (slaughter, plucking feathers).

8. Stock up on water and nonperishable groceries.

Health and Human Services Secretary Mike Leavitt has been telling Americans to stock up on food and water so they'll be prepared if a bird pandemic or some other catastrophe hits. He told a Wyoming audience in early 2006, "When you buy three cans of tuna, buy a fourth, and stick it under your bed."

We heard similar admonitions after 9/11, when bioterrorism was the reason to be prepared. Although scaremongering bothers us, having extra food and water in case of an emergency makes sense. Hurricane Katrina was a frightening example of how "it can happen here." But we're going to keep our little preparedness cache someplace other than under the bed.

Flu virus changes: Drift, shift, and invasion The outer coat of flu viruses is covered with two spiky proteins, hemagglutinin and neuraminidase. The virus uses hemagglutinin (pronounced he-ma-GLUE-ti-nin) to get inside cells and, once it has replicated, neuraminidase to get out and spread. Scientists have identified 16 versions of hemagglutinin and 9 versions of neuraminidase. Flu viruses are named according to these proteins. For example, the bird flu now in circulation is called H5N1 because it has the fifth type of hemagglutinin, thus H5, and the first type of neuraminidase, thus N1. For the immune system, these proteins are the antigens that spur an antibody response. Every year, flu shots need to be a little bit different because of antigenic drift - minor modifications in the hemagglutinin and neuraminidase. Flu pandemics occur when there is a more dramatic change, or an antigenic shift. The shifts seem to occur when animals or people are simultaneously infected with both a bird and human flu virus, so the viruses end up swapping genes. The 1918-19 flu pandemic, the worst one on record, seems to have been caused by a bird flu virus that mutated without mingling genes. Some flu experts worry that H5N1 might mutate in a similar way and stage another "antigenic invasion" that catches human immune systems the world over completely off guard. Antibodies grab surface proteins so a flu virus can't attach to cells. With antigenic drift, the proteins change, so antibodies don't "fit" the proteins, leaving the virus free to attach and infect cells.

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Last updated:	August 21, 2006