The pig is a curiosity in Muslim Afghanistan, where pork and pig products are illegal because they are considered irreligious, and has been in quarantine since Sunday after visitors expressed alarm it could spread the new flu strain.

There are no pig farms in Afghanistan and no direct civilian flights between Kabul and Mexico.

"We understand that, but most people don't have enough knowledge. When they see the pig in the cage they get worried and think that they could get ill," Saqib said.

The pig was a gift to the zoo from China, which itself quarantined some 70 Mexicans, 26 Canadians and four Americans in the past week, but later released them.