An outbreak of Porcine Epidemic Diarrhea virus appears to have spread in Waianae pig farms.

The state Department of Agriculture detected the swine virus at four additional farms in Waianae, according to a news release Tuesday.

No pigs, however, appeared to be sick. 

On Nov. 20, the department’s Animal Disease Control Branch issued a quarantine order restricting the movement of pigs on Oahu after an outbreak of the virus occurred on a farm in Waianae Valley. The virus may cause significant illness in swine and high mortality in piglets.

The virus does not pose a risk to humans or pets. It also is not considered a food safety concern. 

Since the November outbreak, officials say the affected farm appeared to have recovered and the remaining swine do not show signs of illness. 

The quarantine order is still in effect, restricting the movement of pigs on Oahu. Under the order, no swine may be moved east past Nanakuli from Makaha, Waianae and Nanakuli Valley without a permit issued by state veterinarians. It also restricts transporting swine to the neighbor islands from Oahu. 

The swine virus is common in parts of Asia and Europe. 

The virus was first detected in the U.S. in May 2013. To date, 32 states have reported the virus and it’s estimated to have killed up to eight million young pigs. 

The agriculture department noted the strain of the swine virus found in Waianae is a less virulent strain of the disease. 

Veterinarians are continuing to look into how the virus arrived on Oahu. 

There are about 230 pig farms in the state, 70 of which are on Oahu.