The United States is expected to embrace more cases of swine flu because the virus can not be contained, an official from the US Centers for Disease Control and Prevention (CDC) said on Saturday.

"With infections in many different communities as we're seeing, we don't think that containment is feasible," said Anne Schucha, interim deputy director for the CDC's science and public health program.

She told reporters that the CDC was focusing on the transmissibility of the virus, noting that influenza is generally quite transmissible.

The new H1N1 swine flu strain -- a mixture of swine, human and avian flu viruses -- is believed to have killed as many as 68 people and sickened more than 1,000 across Mexico. A total of 24 new suspected cases were reported on Saturday in Mexico City alone, where schools were closed and all public events suspended until further notice -- including more than 500 concerts and other gatherings in the metropolis of 20 million.

Medical team members wear masks as they walk in downtown Mexico City, capital of Mexico, April 25, 2009. [Xinhua]

The outbreak also reached Texas and California in the United States, leaving eight infected. None of the American victims has had any contact with pigs and only one of them has traveled to Mexico recently.

The new strain is still poorly understood and the situation is evolving quickly, Director-general of the World Health Organization (WHO) Margaret Chan said on Saturday in Geneva, adding that it has "pandemic potential".

Although it commonly causes respiratory problems in pigs, swine flu is rare in humans. Only 12 other cases of human infection have been detected since 2005, according to the CDC. Of the 12 cases, 11 of the patients had had contact with pigs.

Symptoms include fever, lethargy, cough and lack of appetite. Documented cases of swine flu being transmitted from one human to another are rare, according to the CDC.

(Xinhua News Agency April 26, 2009)