The U.S. Centers for Disease Control and Prevention (CDC) has warned that Influenza activity is increasing across most of the U.S.

“Reports of influenza-like-illness (ILI) are nearing what have been peak levels during moderately severe seasons,” said Dr. Joe Bresee, the chief of epidemiology and prevention at the CDC’s influenza division. “While we can’t say for certain how severe this season will be, we can say that a lot of people are getting sick with influenza and we are getting reports of severe illness and hospitalizations.”

According to the CDC’s most recent weekly influenza report, the percentage of people visiting a doctor for the flu in the U.S. has been elevated for four weeks, climbing to 5.6%. Last year’s number peaked at only 2.2%. 29 states are reporting high levels of the flu, and 18 pediatric deaths have been attributed to the flu this season.

The CDC is recommending the flu vaccine and antiviral treatment “when appropriate.” Bresee stated that 91% of the viruses analyzed by the CDC this season are similar to viruses included in this season’s flu shot. The match between the viruses in the vaccine and circulating viruses is an indicator of how well the vaccine will work to prevent the flu.

“Anyone who has not already been vaccinated should do so now,” said Bresee. “And it’s important to remember that people who have severe influenza illness, or who are at high risk of serious influenza-related complications, should get treated with influenza antiviral medications if they get flu symptoms regardless of whether or not they got vaccinated. Also, you don’t need to wait for a positive laboratory test to start taking antivirals.”