Swine influenza (aka swine flu) is most commonly a respiratory infection caused by a virus that up to now has been confined to pigs. There have previously been few reported cases of transmission of this disease to human beings.

The swine flu virus is similar, but not exactly the same, as the more commonly known influenza virus that affects humans during the flu season. Both of these viruses attack the respiratory tract — the nose, throat and lungs.

Symptoms are characterized by sudden onset of fever, sore throat, cough, runny nose and generalized body aches. However, unlike the regular influenza, the swine flu is also sometimes associated with symptoms of vomiting and diarrhea.

So far, reported cases of swine flu in the United States have been mostly mild, as has not been the case in Mexico. Most people can expect to recover within one to two weeks without requiring medical treatment. As with regular influenza outbreaks, the very young, the very old and those with chronic illnesses could be at more serious risk of severe complications.

Influenza such as swine flu is easily passed between people through the air in tiny droplets from an infected person when they sneeze or cough. The virus found in these droplets gains entry into a susceptible person through the nose and mouth. People may also become infected by touching something with flu virus on it and then touching their mouth or nose.

It then takes one to four days of incubation before a person develops symptoms. A person with swine flu is contagious from at least one day prior to the onset of symptoms until the symptoms have cleared up.

Laboratory testing to confirm swine flu can be done, but at this time only those with influenza symptoms who have traveled to an area with known swine flu cases in the past few weeks, or who have been very close to someone who has been in those areas, should be tested. If the swine flu is confirmed in our county, then as a precaution everyone with flu symptoms will be assumed to have it and treatment will be determined by severity of those symptoms.

The question of how and when to treat swine flu can be difficult. Although there is no vaccine yet to prevent the infection, there are antiviral medications to treat it. This is an hour by hour developing situation, and there will be advisories regarding the need and availability of medications. At this moment, the only people who would benefit from treatment are those with flu symptoms and have been to areas with confirmed swine flu.

It is imperative that we all do as much as possible to prevent the spread of swine flu. I recommend the following measures:

• If you have flu-like symptoms and have not been in an area of documented swine flu, stay home and treat your symptoms.

• Cover your nose or mouth with tissue and discard the tissue after use.

• Wash hands often with soap and water, especially after sneezing or coughing. Alcohol-based hand cleansers are also effective.

• Avoid touching your nose, mouth and eyes.

• Avoid shaking hands or any close contact with anyone who is sneezing, coughing or who appears ill.

If you develop symptoms of fever, cough aches and sore throat:

• Stay at home and rest.

• Take Tylenol (acetaminophen) or Advil (ibuprofen) in recommended doses. This will treat fever, aches and a sore throat.

• Drink lots of liquids and try to maintain a normal, healthy diet.

See your doctor if you have the following symptoms:

• A fever at or above 104 degrees Fahrenheit.

• Difficulty breathing or shortness of breath.

• Chest or abdominal pain.

• Lethargy or confusion.

• Severe or persistent vomiting or diarrhea.

Please feel free to visit my Web site, valleydoctor.wordpress.com, for more information on the treatment of respiratory diseases.

Terry Hollenbeck, M.D., is an urgent-care physician at Santa Cruz Medical Foundation in Scotts Valley. A doctor with 34 years’ experience, he invites health-related questions at valleydoctor@sbcglobal.net. Information in this column is not intended to replace professional advice. For any medical concern, consult a qualified practitioner.