The H7 strain of Avian Influenza, previously undetected in Asia, has been found in North Korea, which has culled thousands of chickens to contain its first such outbreak, a top U.N. expert said on Tuesday.

Secretive North Korea, struggling with widespread famine due to natural disasters and bad harvests in the 1990s, has culled 219,000 chickens and clamped down on bird movements in a bid to contain the outbreak of avian influenza which has devastated poultry farming in much of Southeast Asia.

“We have a new situation because H7 has so far not occurred in Asia,” Hans Wagner, a senior official with the U.N. Food and Agriculture Organization (FAO), told Reuters Television in Beijing after a week-long visit to North Korea.

“We don’t know where the virus came from, so we have to trace back ... how did the virus come into the farms,” said Wagner, who has played a prominent role in Asia’s battle against the deadly H5N1 virus.

Apart from H5N1, H7 is one of two other avian strains that can cause illness in humans, but previous outbreaks were not as severe as those caused by the H5N1 strain.