The U.S. Navy said on Tuesday that it was postponing an aid mission to the South Pacific after a crew member developed swine flu and 49 others developed symptoms.

The San Diego-based USS Dubuque was scheduled to begin a four month mission on June 1 to deliver medical, dental, veterinary and engineering assistance to Samoa, the Solomon Islands, Tonga, Kiribati and the Marshall Islands as part of America's Pacific Partnership humanitarian program.

Navy Lt. Sean Robertson said the crew affected aboard the 16,900-ton (15,300-tonne) vessel was put on a five-day course of Tamiflu on April 30. The remaining 370 crew members and staff began a 10-day prophylaxis course on May 3. The amphibious transport vessel normally carries 420 crew and about 900 Marines.

"The ship has been cancelled for this. We are looking at options in order to meet the commitments we've made to the countries down there," Robertson said.

Lt Cmdr John Daniels said the navy was using "using prudent judgment" in cancelling the deployment of the USS Dubuque. He added that the mission would still go ahead at some point but the USS Dubuque would no longer be part of it with officials looking at other alternatives to meet the mission's objectives.  

In an earlier report the World Health Organization (WHO) said that 1,516 cases of the new H1N1 virus also known as swine flu cases had been verified in 22 countries. After Mexico, the US has seen the greatest number of laboratory-confirmed infections, at 421, though most cases barring two fatalities have been mild and not required hospital treatment.

The second US resident believed to have died from swine flu was a woman from Cameron County, close to the US border with Mexico said the Texas Department of State Health Services (DSHS). They however added that she had been suffering "chronic underlying health conditions".

A Mexican toddler who died of the virus in the US in April was the first victim of the virus in the U.S. The DSHS said there are 61 confirmed cases of H1N1 flu reported in Texas.

US Health Secretary Kathleen Sebelius acknowledged that the virus would continue to spread in the United States and elsewhere in the world, and more deaths would follow.

30 Marines on a Southern California military base, the nation's largest, were quarantined after one became the first U.S. serviceman known to have contracted the swine flu virus last week and four were eventually diagnosed with the strain.

The WHO said a global pandemic remains a threat as the number of infections has continued to grow worldwide and has urged nations to remain vigilant in spite of the apparently relatively mild nature of swine flu.