New bat virus may cause serious respiratory tract illness in humans

Washington, June 28 : A team of researchers from the Commonwealth Scientific and Industrial Research Organization (CSIRO) has discovered that bats are the likely host of a new virus that can cause a serious, but apparently non-fatal, respiratory tract illness in humans.

Led by Dr. Linfa Wang, the Project Leader for the Molecular Detection group at the Australian Animal Health Laboratory (AAHL), the researchers identified the new virus called Melaka, named after the location in Malaysia where it was isolated in early 2006 from a human patient who showed signs of fever and acute respiratory illness.

During the study, reported in the journal Proceedings of the National Academy of Sciences of the United States of America (PNAS), the researchers used scientific techniques including virology, serology, electron microscopy, and to establish whether the virus was a reovirus and, if so, to what species group it belonged.

'There are a number of different reovirus groups, however only two reoviruses have been isolated from bats in the past,' Dr Wang says.

Scientists had isolated Nelson Bay reovirus from a fruit bat in New South Wales in 1968, and in 1999, another reovirus called Pulau virus was isolated from fruit bats on Tioman Island in Malaysia.

'Our research indicates Melaka virus is closely related to the two previously discovered bat-borne reoviruses, in particular Pulau virus,' Dr Wang says.

His report, titled 'A previously unknown reovirus of bat origin is associated with an acute respiratory disease in humans', talks about three significant discoveries that include evidence suggesting Melaka virus can not only infect humans and cause disease, but can also be transmitted from one person to another.

The retrospective research highlighted that several other members in the same family developed similar symptoms approximately one week later, and showed serological evidence of infection with the same virus.

'The delay in symptom onset suggests human-to-human transmission took place. This type of groundbreaking discovery, the discovery of Melaka virus, is going to make future diagnoses of unknown viruses more accurate, as we can now add it to the list of new and emerging viruses,' Dr Wang says.

The researchers say that they examined bats as a host not only because previous unknown viruses had been found to have originated in bats, but also because epidemiological tracing revealed that the family were exposed to a bat in the house one week prior to the time when the patient started showing clinical symptoms of the virus.

'Bats are known reservoir hosts of an increasing number of zoonotic viruses (animal viruses capable of also infecting people), but they rarely display clinical signs of infection. Although we have not yet obtained direct experimental evidence that Melaka virus originated in bats, we suspect this is the case because not only were the family exposed to a bat, Melaka virus is also closely related to two other bat borne reoviruses - Pulau and Nelson Bay virus,' Dr Wang says.

He also said that he was planning to continue working closely with the group in the National Public Health Laboratory and other Malaysian scientists to identify how widely distributed the virus is, and how many related viruses there are in the bat reovirus group.

'This type of groundbreaking discovery, the discovery of Melaka virus, is going to make future diagnoses of unknown viruses more accurate, as we can now add it to the list of new and emerging viruses,' Dr Wang says.