A newly discovered virus that killed a Saudi Arabian man in June and is now causing life-threatening illness in a person from Qatar is similar to strains carried by bats, researchers reported Thursday. (Ian Waldie/Getty Images)

The newly discovered virus that killed a Saudi Arabian man in June and is now causing life-threatening illness in a person from Qatar is similar to strains carried by bats, researchers reported Thursday.

Most of the bat strains do not infect people. Why the new strain does — and how it got into two unrelated people from the same part of the world months apart — is a mystery being urgently investigated by scientists in Europe, the Middle East and the United States.

The new bug is a coronavirus, a family that includes the agent of severe acute respiratory syndrome (SARS), which caused more than 8,000 infections and 900 deaths in 2003. The SARS coronavirus is also carried by bats.

“It is perplexing. But it is the very early days,” said Nick Phin, an epidemiologist at the British government’s Health Protection Agency who is helping investigate the case of the Qatari patient, who is in an intensive care unit of a London hospital.

The goal is to determine as quickly as possible whether the new virus is a threat to public health or a one-off event that in less vigilant times might have been missed entirely. So far there is no evidence of other, unexplained cases of severe pneumonia with kidney failure, which are the hallmarks of the two cases.

“We should keep our feet on the ground. Two birds don’t make a summer and two patients don’t make an outbreak,” said Ron A.M. Fouchier, a virologist at Erasmus Medical Center in Rotterdam. Fouchier determined the gene sequence of the new virus and posted it for other investigators to see and use.

With no sign that the virus is transmitted from person-to-person or is easily picked up from animals, the advice to the public “has to be go about your normal business,” Phin said.

Fouchier’s laboratory isolated the new coronavirus from lung tissue from a 60-year-old Saudi man who was admitted to a hospital in Jeddah on June 13 and died June 24.

The Qatari patient became ill on Sept. 3 and was hospitalized in Doha a few days later. On Sept. 11, he was sent by air ambulance to England. There, a coronavirus was isolated from lung fluid and partially sequenced.

The Qatari man had recently visited Saudi Arabia. But he returned home more than 10 days before he became ill, according to a report by the European Center for Disease Prevention and Control in Stockholm. Because the incubation period for coronavirus infections is about a week, that suggests he acquired the virus in Qatar, not Saudi Arabia.

Fouchier said Thursday the virus from the Qatari patient is 99.5 percent identical to the one from the Saudi patient, confirming both were infected with the same strain.

The researchers assume the virus caused the patients’ illnesses, although that has not been proved. Coronaviruses are one cause of the common cold. It’s possible the new virus could be another one of them.

To test the strain’s virulence, Fouchier’s lab will infect macaque monkeys and ferrets with it. Ferrets are considered good models of human respiratory infections, and macaques were used to prove the pathological effects of the SARS virus.

“We want to see whether this virus really causes severe disease,” Fouchier said.

Fouchier’s lab has also collaborated with a lab at the University of Bonn and the British Health Protection Agency to make a diagnostic test using gene probes and polymerase chain reaction (PCR) devices, which is available now.

A key question is whether the two cases are tips of an iceberg, with lots of other cases going unseen. To help answer that, epidemiologists are interviewing about 80 people with recent contact with the Qatari man — family, friends, hospital workers, the air ambulance crew.

“We’ve not had an indication that any of the family or any of the contacts were ill,” Phin said. Blood samples are being drawn to see if anyone has antibodies to the new virus, which would suggest they had been infected without knowing it.

How the men became infected is unknown. The Qatari is too ill to be interviewed.

The SARS outbreak apparently started when one or more people picked up the virus from exotic animals, such as palm civets and ferret-badgers, in live markets in China.

Research after the epidemic, however, revealed it was a new arrival in those species, as it was found only in the market animals and not in wild ones. How it got into them — whether directly from bats or through another intermediate host — is still unknown.

The SARS experience suggests that the new coronavirus may also have animal carriers other than bats.

The Qatari patient had “contact with camels and sheep,” Phin said. “But a lot of people in the Middle East have contact with camels and sheep. We are not aware of any exotic exposures.”

He would not describe the man’s work or lifestyle because of patient confidentiality. A review of whether the Saudi patient who died had any unusual animal exposures is underway.

Unusually silent in the investigation is the Centers for Disease Control and Prevention, the U.S. government’s epidemiology agency that is usually out front in outbreaks of strange or new diseases.

“We are willing to help anyway we can,” said Tom Skinner, a CDC spokesman. He would not say whether Saudi Arabia or Qatar had asked for help in investigating the cases or if a team of epidemiologists would be dispatched.