Photo/Illutration A report on four patients of COVID-19 whom doctors treated at Toshima Hospital in Tokyo. The report was released on the Japanese Association for Infectious Diseases website. (Ryosuke Nonaka)

Doctors treating four patients who developed severe cases of COVID-19 after they disembarked from the stricken Diamond Princess cruise ship called for paying close attention to cases, saying the disease progresses rapidly in a short period.

The patients were in relatively stable condition when they were admitted to the hospital, but their health deteriorated quickly over a few days after some needed supplementary oxygen, the doctors said in a report.

The doctors at Toshima Hospital in Tokyo also said close monitoring of patients will be needed even if their respiratory status is stable at the beginning of hospitalization.

The report was released on the website of the Japanese Association for Infectious Diseases on Feb. 25.

It was compiled by Takuya Adachi, a doctor specializing in infectious diseases at Toshima Hospital in Itabashi Ward and his colleagues at the hospital.

The report described the conditions of the four patients, all males. Two of them needed respirators. One is in his 60s, two are in their 70s and one is in his 80s.

After their infections were confirmed while aboard the ship at Yokohama Port, they were taken to the hospital.

All except for one in his 70s complained of high fever, fatigue and coughing. When they were admitted to the hospital, they were running fevers of 37.2 degrees to 38.5 degrees.

But the man in his 70s did not display any symptoms.

After calling an emergency meeting of the ethics committee, doctors decided to use anti-HIV medicine for the patients for 10 days.

Two patients--one in in his 60s and the other in his 70s--were suffering from high blood pressure.

As their fevers did not subside even after they were hospitalized, doctors administered antifebrile, a fever-reduction agent, to them.

Then doctors supplied supplemental oxygen and administered anti-HIV medicine to them. They remained on that course of treatment.

The other two patients are on respirators as their health has worsened.

The man in his 80s, who had high blood pressure, was also administered an anti-HIV drug.

On the 13th day since developing symptoms, the man was put on a respirator. He fell into shock and required dialysis treatment.

But as his respiratory condition did not improve, he was transferred to another hospital where advanced therapy is available.

The patient who showed no symptoms when he was confirmed with infection began developing a fever between 38 and 39 degrees repeatedly since the third day of hospitalization.

Doctors used anti-HIV medicine to treat him. On the 14th day, he was put on a respirator. Although his condition has improved somewhat, he remains under treatment.