Swine flu: How serious is the global threat?

Q: What's the real story about swine flu? I've heard it's the next global pandemic, but I'm not sure what that means.

No name / No state given

You're not alone in your confusion about the current swine flu outbreak, which seems to have started in Mexico. Since then, the swine flu strain of influenza has also spread to the United States, Canada and many other countries. In June 2009, based on its wide spread to many nations, the World Health Organization declared the swine flu outbreak a global pandemic.

Swine flu is one of the many type A influenza viruses. It's unusual for humans to catch swine flu, but occasional cases occur, usually in people who have contact with infected pigs. Like other flu viruses, the swine flu virus changes its DNA as it spreads, giving rise to a number of subtypes.

Health officials around the world are concerned about the swine flu outbreak because:

• It's caused by a new strain of swine flu virus, which means humans haven't had a chance to develop antibodies that could be used to make a vaccine. The new strain is a variant of a recognized swine flu virus — swine influenza virus H1N1. The new form contains DNA sequences from human and avian influenza viruses, as well as from other strains of swine influenza.
• The infection progresses rapidly. In those most severely affected in the Mexican outbreak, potentially fatal respiratory problems developed after less than a week of coughing, aches and fever.
• In Mexico, the death rate was unusually high among those who developed respiratory distress.

In the United States, the swine flu infected some people who had recently visited Mexico and their household contacts. But, the infection resulted in relatively mild respiratory illnesses in this group.

Why such a big difference in severity? One possibility is that the virus mutated to a less dangerous form around the time it showed up in the United States. Another, more sobering possibility is that the severe illness linked to swine flu in Mexico was the result of viral mutations that haven't yet appeared in other countries — but possibly will in time.

Efforts to understand and contain swine flu are under way on a global scale. Until more definitive information is available, the best response for those outside the most affected areas is to:

• Keep tabs on respiratory symptoms. If you or someone in your family develops symptoms suggesting a cold or the flu, be alert for persistent or worsening symptoms, particularly a high fever.
• Stay home if you're sick. If you do have swine flu, you can give it to others starting about 24 hours before you develop symptoms and ending about seven days later.
• Wash your hands thoroughly and frequently. Flu viruses can survive for two hours or longer on surfaces, such as doorknobs and countertops.
• Take extra precautionary measures if you travel to or live in an affected area.
• If you have a chronic condition, such as asthma or heart disease, it's a good idea to wear a breathing mask when you're out in public in affected areas.
• Be prepared. Ask your health care provider or county health department about infection-control plans in case of a serious swine flu outbreak. The antiviral drugs oseltamivir (Tamiflu) and zanamivir (Relenza) reduce the severity of symptoms.