Federal officials say there are widespread reports of outbreaks in at least five states, and nationwide, the number of visits to hospital has gone up for flu-related illnesses.
CBS News Medical Correspondent Dr. Jennifer Ashton explained the Centers for Disease Control and Prevention is reporting higher than normal flu-like activity in every state, and in five states -- Georgia, Alabama, Mississippi, Virginia and New York -- confirmed influenza.
Video Series: Dr. Ashton's Health and Wellness
Ashton said, "This is not just a bad cold. This is potentially life threatening. Sends over 200,000 people a year to the hospital."
So how do you know your symptoms aren't just from a bad cold?
Ashton said, "The symptoms can be difficult to distinguish but basically fever, you don't have to have a fever, upper respiratory symptoms, sore throat, runny nose, cough, diffused body aches. If you've ever had the flu, your body feels like it's been hit by a truck and headache. Really, those constellations of symptoms are highly suspicious for the flu and you can go to the doctor and be tested for it."
If you catch the symptoms in the first 24 to 48 hours, Ashton said, anti-viral medication can be helpful.
She added, "It is highly contagious, usually spread via respiratory droplets. If you're within six feet of someone coughing and sneezing, you're exposed. And people can be contagious one day before they come down with symptoms and up to a week after they've gotten sick. So potentially, it's very easy to transmit."
And if you recently got your flu shot, you still might not safe from the flu.
Ashton said, "I hear from my patients, almost on a daily basis, 'Oh, I got the flu shot in the past and I still got sick.' A couple of reasons for that: One, it does take two weeks to get the immune protection after you're vaccinated. After you're exposed, you can come down with it. Secondly, people think they might have the flu, but it might not be confirmed, and thirdly, the vaccine is an educated guess -- best match to the strains that are circulating. This year it's a good match, but not always, so again, hit and miss, but it is the best protection to reduce your chances."