Atlanta ? U.S. health officials said Saturday that none of the antiviral drugs and other treatment they had tested were effective against a flu-like disease that has killed at least 54 people and sickened nearly 1,500 others.

They also expanded their travel advisory, suggesting that anyone planning travel to mainland China, Hong Kong, Singapore or Hanoi, Vietnam, “may wish to postpone their trips until further notice.”

“The global epidemic continues to expand,” said Dr. Julie Gerberding, of the Centers for Disease Control and Prevention. “We recognize this as an epidemic that is evolving.”

The CDC has reported 62 cases of severe acute respiratory syndrome, or SARS, in the United States, and at least 35 cases have been reported in Canada, where three people have died.

U.S. health officials believe illness comes from a new form of coronavirus, the virus that causes about a fifth of all colds.

Gerberding said Saturday that no successful drugs or treatments had yet been found.

“We have no evidence that any specific antiviral, steroid treatment or other agents that are targeting this virus have any benefit to patients,” she said.