U.S. health officials are preparing for a second wave of the winter flu season, complicated this year by similarities between flu symptoms and those of the coronavirus that has killed more than 1,500 in China and spread fear around the world.

A first round of seasonal flu, caused by a strain of influenza B, named B-Victoria for the city in which it was discovered, peaked in the United States in late December and then dropped off, according to the U.S. Center for Disease Control and Prevention.

However, the CDC says a second round of flu began in late January, caused by a strain of influenza A that is related to the swine flu that first appeared in 2009, and cases continue to increase.

While there have only been 15 confirmed coronavirus cases in the United States as of Friday, health officials have expressed concern that if the virus were to spread in the country, it could initially look like the spread of seasonal flu.

Coronavirus testing

In part to address these concerns, U.S. health officials announced they would begin testing some patients who have flulike symptoms for coronavirus in several U.S. cities.

The testing will initially be carried out by public health labs in Los Angeles, San Francisco, Seattle, Chicago and New York, which are already testing for seasonal flu.

Nancy Messonnier, director of the National Center for Immunization and Respiratory Diseases, told reporters in a telephone briefing Friday that labs will conduct the coronavirus test on patients who show flulike respiratory symptoms, but who test negative for the seasonal flu.

Both the seasonal flu and coronavirus cause respiratory illness, fever and cough. Other typical flu symptoms include sore throat, muscle aches, runny nose and fatigue, according to the CDC.

While scientists have studied the flu for decades, little is known about this coronavirus, dubbed COVID-19, because it is so new. Health officials are still trying to understand all the symptoms related to the new virus, as well has how it spreads and how often cases are severe. There have been few studies on the symptoms of coronavirus, however, research suggests patients most commonly suffer from fever, cough and shortness of breath and are less likely than flu patients to suffer from a sore throat and runny nose.

To prevent the spread of the coronavirus to the United States, CDC officials have put in place travel restrictions and quarantine policies for people who recently visited China. However, officials say that strategy would change if the virus were to spread quickly in the United States.

Messonnier said if there were an outbreak of coronavirus in the United States, the CDC would call for "social distancing" strategies that would include online schooling, teleworking, and canceling mass gatherings, in an effort to prevent people from spreading the virus.

Flu kills 14,000 in US

While health officials put plans in place for any possible outbreak of coronavirus, doctors around the United States continue to help patients battle the seasonal flu. The CDC estimates that 26 million Americans have gotten sick with flu this season and around people 14,000 have died.

Health officials say the first wave of the flu, a B strain, has hit children particularly hard this season, causing 92 deaths in children. B strains are more likely to cause a more severe illness and death in children. Cases of the flu among the elderly have been down this season.

The CDC says concern about coronavirus might have prompted more people with flu symptoms to go their doctor for testing this season, although they say there is nothing in their data to confirm this. Messonnier said if more people are going to the doctor that is a good thing. "

People being a little worried and seeking care doesn't especially worry me, because that's the point," she said.