Avian Flu Explained
Q: What do you think will happen with avian flu?
A: Things could go three ways. The good scenarios would be either sporadic human cases as has happened over the past few years, or an ultimate fading away like SARS. The bad scenario would be a major pandemic. The hope is that a great vaccine for avian flu will be developed before a crisis emerges.
Q: What is a pandemic?
A: When a disease spreads worldwide and beyond its usual severity, it is a pandemic. There were three major flu pandemics in the 20th century: 1918-19, 1957-58 and 1968-69. An epidemic occurs when a disease spreads over a large area, such as a city, country or even a continent.
Q: What is the difference between avian flu and seasonal flu?
A: Avian flu is caused by a virus that normally affects only birds, and seasonal flu is caused by a virus that can be easily transmitted from person to person and does not make birds ill.
Q: Are there different types of flu?
A: There are three main strains of flu and in a typical flu season there are one or more strains circulating. A & B can become epidemic, with A causing the most severe epidemics. C is milder and doesn't become epidemic.
All flu viruses have these surface structures called hemagglutinins and neuraminidases that allow them to attach to and invade cells. Avian flu is a type-A strain and is also known as an H5N1 virus, referring to the particular family of hemagglutinin and neuraminidase. Our immune response to flu is directed against these specific structures, and a vaccine would be developed based on them.
Q: Why is avian flu so dangerous?
A: Avian flu is dangerous because it affects young, healthy people and causes rapid organ failure and death. This is reminiscent of the influenza epidemic of 1918-19 that killed up to 100,000,000 people around the world.
While we're worried about an avian flu pandemic, we still have the seasonal flu every year, which results in 36,000 deaths and over 100,000 hospitalizations. The flu is the most common cause of viral death in the U.S.
Normally, the flu itself is not a direct killer. Most seasonal flu-related deaths occur in those already compromised health-wise, such as the very young and the elderly, and those with other underlying diseases.
Q: How does the flu spread?
A: All flu viruses are primarily spread through coughing and sneezing. Large droplets of saliva contain viral particles that can be deposited on surfaces. People pick up the particles by touching these surfaces or by shaking hands and picking them up from skin. Thus, we want to emphasize the use of handkerchiefs and good cough and sneeze hygiene, which means covering your nose and mouth with your hand or a tissue and cleaning hands afterward.
Avian flu is a virus that spreads among birds, and it can be transmitted from birds to humans under certain conditions, as has happened in 252 cases. In almost all these cases, the humans affected have had direct and very close contact with sick birds. Since 2003, of the 256 cases of avian flu, there have been 152 deaths. (WHO figures as of 10/31/06)
Medical experts are concerned that at some point the avian flu virus will become one that could be easily - and rapidly - transmitted from person to person. Exactly how and when this might happen is not known.
Q: What are the signs that you have the flu?
A: Signs of seasonal flu come on suddenly within a few days of exposure and include cough, fever, body aches, headache, runny nose, congestion, sore throat and fatigue.
Q: Are the symptoms of avian flu different from seasonal flu?
A: The basic symptoms are similar, but the progression from "a bad cold" to a debilitating illness occurs rapidly (within days). At that point, the patients are too ill to care for themselves and need to be hospitalized. This rarely happens with seasonal flu except in infants and the elderly.
Q: How is flu diagnosed? How do doctors know when it's avian flu?
A: The initial diagnosis is based on symptoms like those above and the awareness that flu is circulating in the community. Doctors are not able to determine whether the symptoms are caused by influenza virus without specific tests such as a viral culture test or rapid identification test. However during periods of known influenza virus circulation, a large fraction of patients with these symptoms are presumed to have influenza.
Q: How can we prevent the flu?
A: Don't get infected - which means closely following healthcare and government instructions. Personal safety includes good cough and sneeze hygiene on everyone's part. Hand-washing is useful. In times of severe flu, it might be helpful to stay home from work or school and limit attendance at large public events such as movies and sporting events. This may be critical if we see the emergence of pandemic, severe avian flu.
Q: How is avian flu treated? Seasonal flu?
A: A vaccine delivered by either injection or nasal spray is available for the 2006-07 seasonal flu. Each year, a new vaccine is developed based on what type of flu strain scientists expect will surface.
Two classes of anti-viral drugs are currently available to treat flu.
One of these classes (containing the drugs amantidine and rimantidine) is not effective at all against avian flu and lost much of its effectiveness for seasonal flu in the past two years.
The newer class of anti-influenza drugs (the neuraminidase inhibitors) works against avian flu in the test tube but has had limited use in people, and there have been failures (including deaths). In some of these failures, the flu virus was shown to have developed resistance to the drugs (oseltamivir and zanamivir).
The best use of these drugs might be preventive: before the infection strikes. If we can prevent the virus from getting established in our bodies, we might be lucky and avoid infection.
Uncertainty about treatment for avian flu still exists. We don't know the best time to start the treatment or the best time to stop it. We're also not sure how much of the drug is needed for the drug to be effective - particularly for prevention.
Other problems surround supply and distribution. How do we insure an adequate supply of the drug? Who should receive the drug if supplies are limited? The two versions available now are either oral or inhaled. It might be very hard to give to young children.
Q: What does the future hold?
A: Efforts to develop an effective vaccine hold the most hope for avian flu. Currently, vaccines are very strain-specific, yet strains continually evolve. That's why we need a new flu vaccine every year. Generally, there's a four- to six-month month turnaround time to identify, develop and mass produce a new vaccine. Scientists right now are trying to make the vaccine development process quicker and vaccines more generic so that all strains of flu can be treated with fewer vaccines. With luck, this will occur before the next large flu pandemic.
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