The Boston Athletic Association is “carefully monitoring” the spread of coronavirus ahead of April’s Boston Marathon after another major race, Japan’s Tokyo Marathon, announced Monday it will only let elite athletes run — shutting out tens of thousands of runners to reduce the risk of mass contagion.

“The Boston Athletic Association is carefully monitoring developments related to the coronavirus,” the BAA said in a statement on Monday. “We will continue to closely follow updates from organizations such as the Centers for Disease Control and Prevention, Department of Public Health, and World Health Organization, and will adhere to any policies put forth by the federal government.

“We have no further comment at the moment but will continue to monitor the situation carefully,” the BAA said.

In Tokyo, only a few hundred elite runners and wheelchair racers will be allowed to participate in the March 1 race, drastically reducing the field. The Tokyo Marathon was expected to have about 38,000 participants.

“New cases of COVID-19 (coronavirus) have been confirmed within Japan,” the Tokyo Marathon wrote to registered runners on Monday. “We have been preparing for the Tokyo Marathon 2020 while implementing preventive safety measures, however, now that case of COVID-19 has been confirmed within Tokyo, we cannot continue to launch the event within the scale we originally anticipated.”

Registered runners will be allowed to defer their entry to next year’s Tokyo Marathon.

More than 500 people in Japan have been infected with the coronavirus, and one has died from the virus.

Dr. Gustavo Ferrer of the Aventura Pulmonary Institute in Miami, a leading pulmonologist focused on the coronavirus, said Tokyo is doing the right thing, and Boston should seriously consider following suit.

“There’s a great chance to increase transmission for the virus when there’s a large conglomerate of people together,” Ferrer said. Of Japan, where the virus is more widespread, he said, “There’s no other option than to limit the race. When people are in large crowds together, that’s when things become a big problem.”

“It’s a tricky situation,” Ferrer said. “Boston is another opportunity for people from all parts of the world to gather in potentially cold weather, which favors transmission of the virus. And when people are in close proximity to each other, that’s when it gets passed from one person to another.”

More than 71,000 people around the world have been infected with the coronavirus, including at least 70,548 cases in China, mostly in the central province of Hubei. More than 1,700 people have died from the virus in China.

The number of cases in the United States is still low, Ferrer noted. As of Sunday, there were 15 coronavirus cases in America. Then 14 American evacuees from a Japan cruise ship who were returning to the U.S. were confirmed to have the virus. Those evacuees will be under 14 days of quarantine at a U.S. military facility.

“We need to remain alert,” Ferrer said. “We still have cases going up. It’s still a significant concern.”

Herald wire services were used in this report.