News about the flu is everywhere. It can be frightening and often confusing. Here are the facts.

Human flu--or influenza--is caused by a virus, usually striking in temperate climates like the United States between October and May. There is also concern about a dangerous new strain that could potentially reach pandemic proportions. How is seasonal flu related to avian flu, and what do we need to know to protect our families?

The specific type of virus that causes the flu is different every year, which is why we need to get annual flu shots instead of a one-time vaccination. Antibiotics don't work on the flu, because antibiotics kill bacteria, not viruses. Public health experts keep close watch on the flu viruses moving through animal populations to predict which ones are likely to spread to people and how likely they are to spread. From that information, new vaccines are developed each year that will work against the particular viral strain that is expected. Vaccine production takes at least six months.

The life cycle of all flu begins in birds. Some birds (wild ducks, for example) can serve as "hosts" for the virus. This means that they can spread it to other birds or farm animals without getting sick themselves. These viruses rarely pose a health risk to humans. But if they mutate into forms that can also infect people, the annual human flu cycle begins.

Scientists have identified at least 144 strains of flu virus. For the past 20 years, viruses from two main "families" have predominated as the cause of annual human flu outbreaks. What makes the "avian flu" different from the seasonal flu that we are already familiar with is that it comes from a virus family that has not been known to infect humans before. This means that no one has developed any natural immunity based on previous exposures. In addition, this form of the virus causes more severe responses in the human body, than what we normally expect from the flu, so the mortality from this virus could be much higher.

Here is a side-by-side comparison of the seasonal flu and the avian (bird) flu.

What else?
Influenza infects about 20% of the population each year. It is the sixth-leading cause of death in the United States, so all flu should be taken seriously. An annual flu shot is the best weapon against catching and spreading flu.

Avian flu is not a new disease. It is simply a new form of seasonal influenza. And while it is important for us to have a good understanding of the potential threats, it is also important to keep this information in perspective. Flu pandemics have occurred ten times in the last 300 years--most recently in 1918-19, 1957-58 and 1968-69. Their seriousness depends on many factors. So far, however, the H5N1 strain does not possess the characteristics necessary to produce worldwide human-to-human infection, and there is no reason for people to panic or to make special efforts to obtain personal supplies of antiviral medications. Information is our best ally in efforts to contain and minimize an influenza pandemic.

This article will be updated regularly.

Last update:   09 January 2006.