U.S. health officials yesterday stepped up efforts to prevent the spread of a dangerous new lung infection that has sparked a global health emergency.

The federal Centers for Disease Control and Prevention warned against unnecessary travel to all of China, Singapore, Hanoi and Hong Kong.

The CDC also outlined detailed measures that people infected with the disease and anyone who comes into close contact with them should take to reduce the risk of transmitting the infection.

At least 62 suspected cases of the disease, known as severe acute respiratory syndrome (SARS), have been reported in the United States in 22 states, including four in Virginia.

Most have been among people who recently returned from parts of Asia, where the epidemic is spreading, but two health care workers and five family members have caught the infection from a traveler.

Authorities are meeting all planes, cargo ships and cruise ships arriving in the United States directly or indirectly from affected areas, removing and isolating any sick passengers, and giving other passengers detailed instructions to look out for symptoms. They include a sudden fever of 104 degrees or above, a cough and problems breathing. Chest X-rays usually show pneumonia.

The incubation period is believed to be between two and seven days after exposure. It is unclear how long someone is infectious.

People suspected of having SARS should stay home while sick and for 10 days after the last symptom goes away, the CDC advised. They should also use common sense, such as covering the mouth and nose when they sneeze or cough.

"If possible, a person recovering from SARS should wear a surgical mask during close contact with uninfected persons," the CDC said. "If the patient is unable to wear a surgical mask, other persons in the home should wear masks when in close contact with the patient."

Anyone living with a suspected patient should wash their hands frequently, consider using alcohol-based disinfectants, and consider wearing disposable gloves when they might have contact with bodily fluids. They should avoid sharing utensils, towels and bedding before they are washed with soap and hot water.