Ebola outbreak

At least five pig farm workers in The Philippines have tested positive for a strain of the Ebola virus that is not deadly to humans, taking the number of human cases to five, the government has said.

The Philippines has suffered an outbreak of the Ebola-Reston virus among pigs, and Health Secretary Francisco Duque said it was possible the farm workers were infected by the animals.

One farm worker was last week confirmed to have been infected by the disease, and Duque said the number of human cases had now reached five.

If a link is proved, it would be the first time humans have contracted the disease from pigs.

World Heath Organisation expert on infectious diseases Julie Hall said the virus still posed ‘low risk’ to human health.

The government quarantined farms in The Philippine towns of Pandi and Talavera after the Ebola-Reston virus was discovered in pigs in July 2008.

Ebola-Reston was first detected in 1989 in laboratory monkeys sent from The Philippines to Reston, Virginia, in the United States. Unlike its African counterparts, it has not proved deadly.

The workers are not the first human case of the Ebola-Reston virus.

Twenty five people who came into contact with the infected laboratory monkeys in 1989 tested positive for the virus. Only one showed signs of sickness, suffering from flu-like symptoms, but quickly recovered.

"We cannot say there was a pig-to-human transmission, but we are concerned and need to better understand this virus," said Dr. Soe Nyunt-U, a representative of the World Health Organisation.

Experts from WHO and two other United Nations health agencies ended 10 days of field tests at the quarantined farms last weekend.

As a precaution, The Philippine authorities stopped a shipment of 50,000kg of frozen pork to Singapore last month. It would have been the country’s first pork exports to the Republic. A ban on all pork exports remains in place.

Tissue samples of 6,000 pigs were tested between July and September last year after an outbreak of hog sickness. To the surprise of the global health authorities, four pigs tested positive for Ebola Reston on the two farms, about 150km apart.

Until then, Ebola Reston had been found only in monkeys, and only in The Philippines.

The health experts are looking at the possibility of fruit bats — source of the dreated Ebola strains in Africa — being the source of the latest virus.