WASHINGTON, May 5 (Reuters) - The U.S. Navy said on Tuesday it decided not to send a warship on a planned humanitarian mission to the South Pacific after one crew member fell ill with the H1N1 virus and 49 others developed symptoms.

The San Diego-based USS Dubuque had been scheduled to sail on June 1 to begin a four-month mission to deliver medical, dental, veterinary and engineering assistance to Samoa, the Solomon Islands, Tonga, Kiribati and the Marshall Islands.

Navy Lt. Sean Robertson said ailing crew aboard the 16,900-ton (15,300-tonne) amphibious vessel were 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 ship has been canceled for this. We are looking at options in order to meet the commitments we've made to the countries down there," Robertson said.

The Dubuque usually travels with a crew of 420 sailors and a detachment of 900 Marines, according to a Navy website.

U.S. officials on Tuesday reported a total of 403 confirmed infections with the new H1N1 virus widely known as swine flu.

While officials in Texas also announced another death attributed to the outbreak -- only the second such fatality outside of Mexico -- most U.S. cases have been mild and not required hospital treatment.

Last week about 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. Four will eventually diagnosed with the strain.

(Reporting by David Morgan, Editing by Sandra Maler)

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