The United States has extended the use of masks on public transport by 15 days, while the country’s top public health agency monitors a recent increase in coronavirus cases.

A federal rule requiring travelers on public transportation such as planes, trains and buses to wear masks is set to expire on April 18.

“In order to assess the potential impact of increased cases on serious illness, including hospitalizations and deaths, and on health care system capacity, the CDC order will remain in effect at this time,” the CDC said.

“The Transportation Security Administration has decided to extend the safety directive and emergency amendment for 15 days through May 3, 2022,” the CDC continued.

The public health agency also said it would change its international travel alert system so travelers would only be warned to avoid visiting a country in exceptional circumstances, such as the emergence of a dangerous new variant, and not anywhere Covid-19 is spreading. 19 is considered very high. This level 4 category currently applies to a wide range of countries, including most of Europe and Australia.

The Biden administration has been under pressure Tourism and Republican politicians lift mask mandates. Domestic airline executives cited threats to the safety of airline employees as their main task is to wear masks.

The Transportation Security Administration, which oversees airport security, said in March that the government agency was working with the CDC to develop a “revised policy framework” for when and under what circumstances masks should be required on public transportation.

Covid-19 cases are “starting to rise slightly,” particularly in areas such as northern New England, New York, Colorado and Washington, D.C., said David Dowdy, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health.Philadelphia became the first major U.S. city on Monday Re-implementing indoor mask rules.

Airlines are also calling for an end to pre-departure testing requirements for international travel. The cancellation of them is expected to further increase travel demand.