Doctors have warned that many coronavirus patients, especially younger ones, are suffering aftereffects for a long time despite subsequently testing negative for the virus and are calling on the government to take countermeasures.

The aftereffects include malaise and difficulty breathing. In severe cases, patients became bedridden even though they had been diagnosed with a mild case of the COVID-19 disease caused by the virus.

So far in Japan, there are not many medical institutions that treat patients suffering from such long-lasting effects.

"Most of them are in their 40s or younger. The government needs to take the issue seriously and implement countermeasures," one of the doctors said.

In Japan, the National Center for Global Health and Medicine conducted a telephone survey last year on coronavirus patients who had been discharged from hospitals. They collected answers from 63 individuals.

The survey found that in some cases, people continued to experience difficulty breathing, malaise, and olfactory disorders four months after they started showing COVID-19 symptoms.

There were also cases where patients experienced hair loss several months after the disease developed, the center said.