Viral outbreaks raise the question: Who’s minding the ship?

Your cruise liner may look shipshape, but what about bacteria and viruses, dangers you can’t see? Is anyone monitoring those?

It’s a natural question considering the string of cruise ships that have limped into port in recent weeks, each carrying dozens of people sickened with gastrointestinal illness. Ships run by Disney, Holland America, Carnival and Britain’s P&O; Cruises are among those that have collectively reported hundreds of cases of the illness, which typically causes vomiting and diarrhea and lasts one to three days.

Cruise sanitation is stringently monitored, but even the strictest on-board regimen cannot prevent all outbreaks, especially those caused by viruses.

“You’re never going to get rid of them,” Dr. Frederick Southwick, chief of infectious diseases at the University of Florida College of Medicine, says of such outbreaks. He calls a ship the “perfect vehicle” for transmitting the so-called Norwalk-like virus, suspected in the most recent cases.

“You’ve got a large number of people in a small environment,” he says. The virus spreads rapidly by person-to-person contact. Typically, you get infected when you touch an infected surface, then your mouth. Just one ill person on board can infect many other passengers, he says.

The federal government and the cruise lines, in a cooperative program of inspections and investigations run by the federal Centers for Disease Control and Prevention, have been trying for three decades to eliminate gastrointestinal outbreaks aboard cruise ships. They can claim considerable progress.

In the 1970s, when ship inspections began, there were 12 to 15 outbreaks of diarrheal illness each year aboard cruise ships, the CDC says, attributed to various causes. The number fell steadily; in 1999 there were only three outbreaks.

This decrease occurred even though the number of North Americans taking a cruise quadrupled from 1981 to 1999, to 5.9 million per year, according to Cruise Lines International Assn., which represents about 95% of the berths marketed in the U.S. and Canada.

Early data show that the per-passenger rate of such outbreaks is actually decreasing, says Dave Forney, chief of the CDC’s vessel sanitation program, although CDC statistics from 2000 to 2002 were not available as of the Travel section’s press time Tuesday. Recent outbreaks reported by Holland America, Disney and Carnival affected about 10% or fewer of passengers.

The CDC program requires ships to report all gastrointestinal cases. An outbreak that affects 2% or more of those aboard typically triggers a CDC investigation.

Also under the program, CDC staff twice a year inspect each passenger ship that has an international itinerary, calls on a U.S. port and carries 13 or more passengers. There are 154 ships on this roster, counting all the major cruise lines and some minor ones. Owners pay a fee, based on their ship’s tonnage, to finance the program. (Ships that sail only domestically, such as the Delta Queen, are under jurisdiction of the Food and Drug Administration.)

The inspectors arrive unannounced. Depending on the size of the vessel, up to four may be assigned, and the inspection may take up to eight hours.

“This is an extremely stressful day for most cruise ships,” Forney says.

The program’s operations manual sets detailed standards for water systems, food handling, swimming pools and spas. During inspections, each of 41 criteria, with labels such as “hands washed; hygienic practices,” is assigned 1 to 5 points, totaling 100. Points are deducted for violations.

It’s a hands-on task. “We take out the thermometer and check the buffet,” Forney says.

Ships must score 86 or higher to pass. If they don’t, they can request a reinspection after taking steps to correct the problems.

Most ships work hard to pass the inspections, and most succeed. The scores are posted on the Internet at www.cdc.gov/travel. (Click on “green sheets” under “Cruise Ships and Air Travel.”) Only four ships on the current list failed.

I suspect most home kitchens wouldn’t pass these tests. I know mine wouldn’t.

A review of recent CDC reports shows that scores may be imperiled because of “old food residue ... in the corner of dairy cooler,” “cut cheese was not date-labeled” or “the blade assembly of the can opener was not easily cleanable.”

On the other hand, some violations were egregious, such as kitchen workers “observed handling soiled equipment and then handling clean equipment without washing their hands first” and food in a refrigerator registering up to 54 degrees.

During inspections before their recent disease outbreaks, Holland America’s Amsterdam scored 96 (in June), Disney’s Magic scored 99 (in June), Carnival’s Fascination scored 93 (in July) and P&O; Cruises’ Oceana scored 95 (on Nov. 29).

“We have not identified any problems with food handling or the water,” Forney said of the CDC’s subsequent investigations of the Amsterdam and Magic; reports were pending on the others.

That is part of the dilemma. Much of the CDC twice-yearly inspection focuses on practices that may promote bacterial growth, such as poor refrigeration, although some of its standards, such as hand-washing and sanitizing food surfaces, may help reduce the number of viruses too, Southwick says.

Yet most gastrointestinal illnesses are believed to be caused by viruses, not bacteria. The Norwalk-like virus is hardy, resisting heat and most chlorine compounds, and is “very hard to find,” says Southwick of the University of Florida College of Medicine.

He notes that countless Americans who have never stepped on a ship are made ill each year by the very common Norwalk-like virus.

Unlike the cruise lines, however, they aren’t required to report it.

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Jane Engle welcomes comments and suggestions but cannot respond individually to letters and calls. Write Travel Insider, Los Angeles Times, 202 W. 1st St., Los Angeles, CA 90012, or e-mail jane.engle@latimes.com.