The government plans to more than triple the number of quarantine stations at airports around the country and hire scores of health officers as part of a broad plan to try to stop deadly infectious diseases from entering the United States.

Ten new stations, at airports stretching from Alaska to Puerto Rico, are already open or nearing completion, and about 50 new health officers are undergoing training. The Centers for Disease Control and Prevention plans to build an additional seven stations as soon as it can get the money. Eight stations that have existed for years are gaining staff, so that when the plan is complete, the country will be blanketed by a network of 25 centers designed as a first-line of defense against a global disease pandemic.

In practical terms, the plan will not mean much change for international air travelers, at least in normal times. It does mean that if a passenger gets sick on a flight, when the plane lands it is likely to be boarded by federal health officers specifically trained to recognize exotic diseases, not just by local emergency crews.

If a global pandemic looms, though, the plan calls for the centers to play a key role in setting up a firebreak that would try to keep the disease out of the United States. The stations would help coordinate broad programs under which thousands of air travelers might be subject to medical evaluation, or offered medical pamphlets and advice, before being allowed to enter the country. Federal experts emphasized that passengers would be quarantined only if there is strong reason to suspect they have been exposed to a serious disease, and then only long enough rule out that possibility or get them into medical-isolation wards at hospitals.

"We're not going to lock you up for days," said Jennifer Morcone, a spokeswoman for the CDC, noting the negative connotation the word quarantine once carried. "The goal here is to take care of people."

Many of the new centers are being housed temporarily in small offices or suites, but eventually they will include examination rooms that will allow health officers to isolate and evaluate a few ill passengers at a time, according to the CDC. The centers will never be big enough to quarantine entire planeloads of people but would play a coordinating role if such drastic measures ever became necessary.

Washington Dulles International Airport is getting a new center, with some staff already in place and construction underway on a small office suite. Other centers are opening this year at airports in Anchorage, Boston, Detroit, El Paso, Houston, Minneapolis, Newark, San Diego and San Juan. Quarantine stations have existed for years in Atlanta, Chicago, Honolulu, Los Angeles, Miami, New York, San Francisco and Seattle, but all those are growing.

The CDC aims to open at least seven more quarantine offices when it can get the money, to bring the national total to 25. Cities at the top of the priority list include Charlotte, Dallas, Denver, New Orleans, Philadelphia and Phoenix, but that list is not final and other cities are under consideration.

The 50 or so staff members already hired will more than double the CDC's presence at the nation's airports. Leaders of most of the new and existing stations convened last week in a suburb of Salt Lake City to develop operating procedures.

The CDC's plan calls for placing at least one doctor, not just inspectors, at every airport with a quarantine station. Up till now, even in long-established stations, the nearest CDC doctor was often hundreds of miles away. "This is a dramatic change from where we were a year ago," said Ram Koppaka, acting director of the CDC's quarantine branch.

The plan is a response to rising fears about bioterrorism or a potential pandemic of respiratory illness. For example, experts fear that a highly lethal form of influenza now circulating among birds in Asia, if it undergoes certain genetic changes, could start spreading rapidly among humans, potentially killing millions. In an age of global air travel, such an illness could jump from foreign countries to the United States in hours.

The plan is also an attempt to apply lessons from the 2003 scare over a new disease: severe acute respiratory syndrome, or SARS. Hundreds of thousands of people around the world, including thousands in Toronto, were placed in quarantine and entire cities in China were cordoned off before that ailment was brought under control. It never gained a foothold in the United States, but a few cases came in on planes, and the CDC found itself scrambling to notify potentially exposed passengers.

"We recognized that in SARS, we had a tremendous need for CDC public health officers at points of entry to our country in order to evaluate passengers who had potential exposure in transit," said Julie L. Gerberding, director of the CDC, in Atlanta. "In many of our airports, we don't have on-site facilities to isolate someone who is potentially infectious."

The CDC's plan is winning plaudits from outside experts who are familiar with it. But they cautioned that not even a dramatic expansion of the CDC's presence at airports can guarantee that an infectious organism will not slip into the country. And some noted that recommendations for just this kind of program had been around for years.

"I actually applaud the CDC on this," said Michael T. Osterholm, director of the Center for Infectious Disease Research and Policy at the University of Minnesota. But he added: "We should have done this a long time ago. Once someone leaves a plane in this country, they get lost into the veneer of humans wherever they go."

The CDC is still developing its plan for the centers and weighing related issues, such as how to notify passengers if an illness is discovered after everyone leaves a plane. That proved a huge problem during the SARS scare, with airlines often unable to supply final destinations or detailed contact information for their passengers.

The day may be nearing when people will be asked for such details as they log onto the Internet to make plane reservations. In a public-opinion survey for the CDC, Harvard University researchers found a strong willingness to comply if people were assured their data would be used only in an emergency.

"If we set up these quarantine centers and find out the passenger in 7B has some sort of suspicious respiratory condition, we need to know immediately who was in 7A and who was in 7C," said Mark A. Rothstein, a bioethicist at the University of Louisville who led a team that studied the CDC's response to SARS. "To wait for paper records could take days -- the whole country could be infected by that point."

Staff writers David Brown and Sara Kehaulani Goo contributed to this report. Brown reported from Atlanta.

The quarantine station at John F. Kennedy International Airport in New York is among the eight original centers that have been operating for years.