By Dr. Sanjay Gupta
CNN Your Health

If you have not already received your flu shot, it is time. Flu season begins in October and peaks between February and March.

The flu kills about 20,000 people every year, according to the Centers for Disease Control and Prevention.

This year, there are three strains of the virus that are expected to be particularly common: the Moscow, the New Caledonia and the Hong Kong.

It is important to remember that there are differences between a cold and the flu. Cold symptoms are typically just upper respiratory and symptoms include a runny nose and sniffling.

The flu tends to be much more serious, affecting the lower respiratory system as well. Fevers, fatigue and sore throat are present with the flu -- not to mention just a general feeling of being wiped out.

The flu shot will reduce your chances of getting the flu by about 70-90 percent, according to the Advisory Committee on Immunization Practices (ACIP). It does take 14 days to work so make sure to get your flu shot before you get sick.

Thank you for reading "The Pulse," my weekly column on top health and medical news. Here are other stories making headlines this week.

Obesity on rise among Americans

If there was ever a doubt, it is now official: Americans are getting fatter.

More than 30 percent of people in the United States are obese, according to a survey by the Centers for Disease Control and Prevention.

That's up 23 percent from the 1988-1994 survey.

The picture for children is equally bleak. More than 15 percent of those between the ages of 6 and 19 are now overweight.

Researchers blame increasing food portion sizes, the consumption of high-fat fast foods and increasingly sedentary lives.

Click here for more on the study and to find out how your weight rates.

Reducing the risk of SIDS

Putting infants on their backs to sleep greatly decreases the risk of Sudden Infant Death Syndrome, according to researchers who conducted the most definitive study of its kind in the United States.

Researchers found that the number of SIDS deaths was two to three times higher in African-American communities, and almost three times higher among Native Americans.

SIDS is the leading cause of death among infants 1 month to 1 year old.

Click here for a list of tips on how to prevent SIDS.

Tracking the West Nile virus with satellites

The fight against the West Nile virus may soon be out of this world.

NASA researchers are developing tools that will allow public health officials to better track and predict the spread of the virus using satellites.

Mosquitoes transmit the virus from infected birds to other birds, animals and humans. Variations in temperature and vegetation levels dictate where the mosquitoes and birds thrive.

Satellite pictures could give scientists a "bird's-eye view" of high-risk areas and help in the prevention and early detection of the virus.

Click here to find out how satellites are helping track the spread of the disease.