A mysterious outbreak of a deadly disease that killed one man and 14 racehorses and then subsided as inexplicably as it had begun has been traced to a new virus by researchers in Australia, where the outbreak occurred.
The virus, which has not been named, belongs to the morbilliform family, which includes the measles virus, the researchers report in today’s issue of Science. It is the first new virus in the family to attack humans since the measles virus was identified in the 10th century.
Its leap from an animal to a human, where it proved fatal in the first case detected, raised fears among scientists and health officials of the type inspired by recent books and movies about the very real threat of new and emerging viruses.
The virus produces a high fever, a rapid buildup of fluid in the lungs and bloody froth from the nose. The devastation comes from damage to blood vessels.
In one of the quickest discoveries in the annals of veterinary medicine, scientists identified the new virus just 12 days after the outbreak had been detected on a farm near Brisbane last September.
A team led by Dr. Keith Murray, of the government’s top-security Australian Animal Health Laboratory in Geelong, quickly was called in to try to identify the virus, which already had killed some horses and had infected two humans.
One of the humans, a 49-year-old horse trainer, died after six days in intensive care from a severe lung infection known as interstitial pneumonia. The second, a 40-year-old stable hand who had helped care for a dying mare, developed a severe influenzalike illness but recovered on his own.
Scientists speculate that the virus is spread by nasal secretions or saliva. They are conducting studies to determine when, during the course of an infection, the virus is most likely to be transmitted.
Diagnostic tests developed by Murray’s team showed that the outbreak was over quickly. No other cases were found in horses or humans. But the team was unable to establish where the virus had come from, nor can it explain why the virus suddenly appeared in horses in Australia.
The Australians are preparing more material for tests which may determine whether the virus may have caused hitherto unexplained cases of lung infections and other illnesses.
Dr. Brian Mahy of the Federal Centers for Disease Control and Prevention in Atlanta said Murray would visit the centers in the next few weeks to discuss the case.
The quickness with which the discovery was made illustrates a heightened awareness by scientists of the importance of detecting new and emerging diseases.
“We had well-prepared minds and facilities, and we also had a bit of luck,” Murray, a veterinary virologist, said. His facility is designed to handle investigations of zoonoses, diseases of animals that also infect humans.
“It’s Guinness Book of Records stuff,” Murray said with a laugh of the speed of the discovery.
Health officials temporarily canceled horse racing, banned the transport of horses within the area and quarantined the farm. Australians feared damage to the country’s export meat markets.
The outbreak was detected Thursday, Sept. 22. By 1 a.m. on Friday, Murray’s team was testing samples from the dead and dying animals for African horse sickness, which also is a viral infection but one that does not occur in Australia. The results were negative, and by late Friday afternoon, the scientists also had eliminated all other major exotic diseases of horses.
Working through the week, Murray’s team ruled out bacteria such as anthrax as well as insecticides and other poisons.
The scientists saw the herringbone structure characteristic of the parent family of the morbilliform virus. This left them puzzled because no member of that family was known to cause serious disease in both horses and humans.