Four more 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 said Friday.
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 Friday 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 Organization 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.