The head of the government's flu task force panel said Saturday that Japan's biggest challenge from now on will be to prevent young people with other diseases from catching swine flu because it could kill them.

Speaking to reporters after a task force meeting, Shigeru Omi, the leader of the panel, said that diabetics, people with immunodeficiency syndromes, pregnant women and kids 5 or younger are among those most susceptible to H1N1 because it might worsen their symptoms and cause other medical complications.

The meeting was convened after a 17-year-old high school student in Kobe was confirmed infected with the quickly spreading H1N1 flu even though he had never been overseas.

Omi, a professor at Jichi Medical University, said it's likely the new flu is already on the move in Japan.

"Infection within a community has already started. We on the panel think we cannot deny the possibility that the infection is already gradually spreading," Omi said.

But he also said the virus is thought to be less dangerous than normal types of flu because its symptoms, at least outside of Mexico, have been relatively mild when compared with other types of flu. He also said that common flu drugs, such as Tamiflu, are effective in treating it.

As for using face masks, Omi recommended using them in crowded places, but said there is no point in wearing one in an open space unless it is "quite crowded."

Given the discovery of the first domestic case, Omi also said the inspections being held to block the new influenza from entering Japan's ports should be "gradually" scaled back.