The patient, whose identity was not disclosed, was isolated and transferred to the hospital north of Stockholm after originally being admitted to the emergency ward of the smaller Enkoping hospital.

The young man had been in Burundi for around three weeks and was exhibiting classic symptoms of haemorrhagic fever, including vomiting blood, the hospital's chief medical officer said earlier on Friday.

The regional authority said the man's condition had improved over the course of the day and that while tests had also ruled out diseases such as Marburg and dengue fever, further examinations were needed to determine the nature of the illness.

Patients at the emergency ward in Enkoping had also been kept isolated pending the test results, as were the man's relatives, but all were now free to go home, it said.

There is no known Ebola outbreak in Burundi but it borders the Democratic Republic of Congo, which has been fighting an outbreak for almost six months. The disease has killed 356 of the 585 people known to have been infected.

The epidemic in a volatile part of Congo is the second worst ever, according to the World Health Organisation.

The largest outbreak was one in 2013-2016 in West Africa, where more than 28,000 cases were confirmed.

Australian Associated Press