CHICAGO (CBS) — Here are the latest developments on coronavirus:

The Centers for Disease Control and Prevention on Tuesday warned Americans that they should not travel to China unless it was necessary.

Citing a reduction in passengers, United Airlines suspended 24 flights to three cities in China, including five operating at O’Hare International Airport (two flights to Beijing and three to Shanghai).

Late Tuesday afternoon, a chartered plane evacuated Americans from Wuhan, China, the city hit hardest by the virus. Its first stop will be Anchorage, Alaska, where they will be screened for the virus. Anybody with the disease will not be allowed to continue into the continental United States, CBS LA reports.

Officials with the Ontario International Airport, 40 miles east of Los Angeles, said it is making preparations for the passengers, where they would be further screened and evaluated for about two weeks.  A statement stopped short of confirming that the flight will land there, but it is an official repatriation center for the West Coast.

Federal health officials say there remain five cases of coronavirus in the United States, and all of them traveled from the Wuhan area. One woman is being treated at St. Alexius hospital in Hoffman Estates.  She is in good condition.

Doctors continue to monitor everyone the 61-year-old encountered since she returned from China two weeks ago.

Meanwhile, DuPage County health workers are tracking down people who came into contact with the infected Chicago woman. They are monitoring anyone who was exposed to the woman for signs of the virus.

Doctors are also taking specimens from the five infected patients in hopes of developing a vaccine. It would still take months to develop, but it could be available if the outbreak becomes serious, officials said at a news conference today in Washington.

The other cases are in California, Washington and Arizona.

At least three daycare centers in Chicago’s Chinatown and Bridgeport areas have also told families to stay home if they have recently visited China. The mandate also applies to teachers.

If kids, parents, or educators have been to China, they are asked to stay away for two weeks.

On Tuesday, China agreed to let the World Health Organization send a team of experts to study the virus.  Among the tasks, the team will try to confirm whether the virus can spread from a person who does not yet show any symptoms.

As Chicagoans continued to stock up on surgical masks, CBS News chief medical correspondent Dr. Jon LaPook said they only provide partial protection. 

“If it’s a droplet, there’s going to be virus in the droplets, so it will help protect it. But remember the virus is so small it can go through the mask,” he said.

Medical screening for the virus has expanded to 20 airports in the United States.  O’Hare was already on the original screening list.  Midway is not screening passengers as it has no flights coming from China.

Overall, the risk to Americans currently is low, federal health officials say.

According to the CDC, signs and symptoms of the illness include fever, cough, and difficulty breathing. This new form of coronavirus has the potential to cause severe disease and death. Available information suggests that older adults and people with underlying health conditions or compromised immune systems may be at increased risk of severe disease.