There are “encouraging signs” that the new H1N1 virus that has raised concerns of a pandemic is no more dangerous than routine seasonal flu viruses that circulate annually, a top U.S. health official said on Sunday.

Dr. Richard Besser, acting director of the U.S. Centers for Disease Control and Prevention, also defended actions taken by U.S. authorities in trying to limit the impact of the new swine flu virus, saying there has not been an over-reaction.

“With seasonal flu, something that hits us every year, we see 36,000 (U.S.) deaths. Here, we’re seeing encouraging signs that this virus so far is not looking more severe than a strain that we would see during seasonal flu,” Besser told “Fox News Sunday.”

Besser said he still expects the virus to have a “significant impact on people’s health.”

“We’re not out of the woods. The information that we’ve been getting over the past couple of days is encouraging,” Besser said.

The CDC said 160 people in the United States are confirmed to have been infected with the new virus, including the death of one Mexican boy who was visiting relatives in Texas. Cases have been confirmed from 21 of the 50 U.S. states, the CDC said.

In Mexico, the country hardest hit by the outbreak, 19 of the more than 100 suspected deaths from the new H1N1 virus have been confirmed.

“We are not over-reacting to this outbreak. With a new infectious disease, there’s a lot of unknown, a lot of uncertainty,” Besser said.

“And you basically get one shot. You get one chance to try and reduce the impact on people’s health. And so what you do is you take a very aggressive approach. And as you learn more information, you can tailor your response,” Besser added.

Health and Human Services Secretary Kathleen Sebelius said health authorities are developing vaccines for the next flu season as well as one specifically to address the new virus.

She said no decision has been made on whether to have full-scale manufacturing of a vaccine for the new virus.

“One of the things that we know is that even if this current situation seems to be lessening, if we are cautiously optimistic, we really don’t know what’s going to happen when real flu season hits with H1N1 virus,” Sebelius told “Fox News Sunday.”

WASHINGTON (Reuters)