Flu activity is ramping up in some parts of the country, even though the season so far has been milder than in recent years.

The Centers for Disease Control and Prevention advised clinicians to treat suspected influenza in high-risk outpatients with antiviral medications as soon as possible. Don’t wait for testing results, the agency says, because early antiviral treatment works best.

The H1N1 viruses (which caused a pandemic in 2009) have predominated in recent weeks, landing some young- to middle-aged adults in intensive care from a severe respiratory illness. Fatalities have been reported, the CDC said. This strain of the virus has been known to cause severe illness in children and young adults.

For treatment to start quickly, patients need to know when to go to the doctor for suspected influenza. Here are some guidelines for determining if you have the flu or just a cold.

Signs

Cold symptoms usually start with a sore throat. Nasal symptoms and a cough often show up around the fourth or fifth days, according to WebMD.com. Fever is possible with a cold, especially in children.

Flu symptoms come on suddenly. Fever and chills are common, along with muscle or body aches. Many flu patients also experience headaches and fatigue, according to the CDC.

Differences

Fever of 101 degrees or above is the most likely indicator of the flu instead of a common cold. Headache and extreme exhaustion are also telltale signs of flu and less common in cold patients.

Prevention

The best defense against both the cold and flu is vigilant hand washing and avoiding close contact with those who have symptoms of either illness. The flu vaccine is also proven effective in preventing the influenza.

Treatment

In many cases, decongestants and pain relievers are the best remedy for symptoms of cold and flu. However, prescription antiviral drugs are available for some flu patients, especially in the early days of the illness. Check with a doctor for more information on this treatment.

Also watch for signs of ear infection (which can result from a lingering cold). Sinusitis, bronchitis and pneumonia can result from flu complications and can be life threatening in some patients.