WASHINGTON — U.S. health officials are expanding their checks of international travelers for signs of a worrisome new virus from China, even as they say the risk to Americans so far is very low.

For “the individual American, this should not be an impact on their day-to-day life,” Health and Human Services Secretary Alex Azar told reporters Tuesday.

China has confirmed more than 4,500 people with the new illness, which can cause pneumonia, and more than 100 deaths. So far, there are five confirmed patients in the U.S., and no sign that they have spread the illness to anyone around them. They had all traveled to the center of the outbreak.

While reports from China suggest that people there may have spread the illness before showing symptoms, there is no evidence of that in the U.S., stressed Dr. Robert Redfield, director of the Centers for Disease Control and Prevention.

And while some other viruses are known to occasionally spread before symptoms are obvious — such as the flu — health officials say that’s far less of a concern than the obviously contagious patients.

The CDC already has been checking arrivals at five U.S. airports that once had direct flights from the hardest-hit section of China. While China has instituted broad travel bans, people who had been in other parts of China still may be arriving via other countries.

The CDC is now beefing up screening at 15 more “quarantine stations” around the country, airports and other places where health workers regularly check arriving travelers for signs of illness.

But travelers may not be sick right then, CDC’s Dr. Nancy Messonnier said. The screenings also are an opportunity to educate travelers that if they develop symptoms — such as fever or a cough — after returning from the outbreak zone, they should contact their doctor, she said. That’s exactly what the first two U.S. patients did.