Ships in Alaska waters and elsewhere under-report shipboard illnesses -- a problem that prevents sicknesses like the flu from being contained more quickly, said a government report released Tuesday.

Masters of ships heading to a U.S. port are required to report certain communicable diseases to the nearest quarantine station of the federal Centers for Disease Control and Prevention. In Alaska, that's in Anchorage.

But the report says reporting of illnesses to state and federal agencies has been "inconsistent." They don't know how many cases go unreported, but they know some illnesses have been reported later than they should have been.

Outbreaks of influenza A among tourists on Alaska cruises in 1998 and 1999 were cited as an example of cases where health officials were only notified "after an outbreak was large or well under way."

The report also talks about an incident in June 2009 when H1N1, commonly known as swine flu, broke out on board an Alaska-bound cruise ship and the industry and health authorities handled it well, according to Shahrokh Roohi, regional officer-in-charge for the CDC's Quarantine and Border Health Services Branch.

Roohi was among CDC staff members who wrote the report, which was released by the Alaska Health Department.

"There's been marked improvement," particularly with cruise ships, in reporting communicable diseases, Roohi said. "Our biggest challenge is probably with the cargo industry."

The report noted Alaska is the top cruise ship destination in the United States, with more than one million passengers in 2009.

Of 2,571 notices of illness or deaths at sea that the CDC quarantine branch received nationally from 2005 to 2009, 227 were received by the Anchorage branch.

Ninety-six percent of the Alaska instances were from cruise ships, and four percent from cargo ships. Most ships were reporting flu-like illnesses. Sixteen percent were reports of chicken pox and 12 percent were death reports.

Reach Rosemary Shinohara at rshinohara@adn.com or 257-4340.