Nadia Paden felt fine when she boarded a flight in San Francisco on Thursday that included a coughing, fussy baby. But she was feeling nauseated herself by the time she landed at Honolulu Airport, the third most likely airport in the country to spread the next great pandemic, according to a Massachusetts Institute of Technology study.

As she waited for a ride home to Waikiki, Paden, 23, said she’s increasingly concerned about contracting someone else’s disease as she travels through Honolulu Airport and into crowded planes.

"I never felt that way before, but I was nauseous when I got off the plane," Paden said. "On an airplane, it’s not like you can crack a window."

Even though Honolulu’s airport isn’t nearly as busy, it’s right behind New York’s John F. Kennedy Airport and Los Angeles Airport — and just above San Francisco, Newark, Chicago O’Hare and Washington Dulles — as "early-time super spreaders" of a pandemic, according to the MIT study published last week in the online journal PLoS ONE.

Honolulu Airport is only 25th in the nation in terms of boardings. But it ranks third highest for the risk of spreading the next pandemic because of three factors: its preponderance of long-distance flights that can allow germs to incubate and spread en route; its central location between Asia and the mainland; and regular connections to "other massive hubs, which are themselves powerful spreaders," the MIT researchers said.

"This is not a big surprise and it should not be a big surprise," said Hawaii state epidemiologist Sarah Park, who oversaw the 2009 H1N1 "swine flu" pandemic that killed 13 people in the islands — most of them on Oahu — and sickened dozens of visitors and residents. "We hope the folks at the federal level who control the money wake up and realize we’re a pretty important place here."

MIT researchers used new modeling to rank Honolulu Airport’s risk of spreading another pandemic.

"But I don’t need a mathematical model to tell me Hawaii is a big mixing pot," said Chris Whelen, director of the Hawaii state laboratories. "We are a traffic-centric location with lots of trade and military going through and a lot of people who are in the airport for a long time. We’re a long way away from our nearest neighboring state, so we’ve got to take care of business here best we can, as we did during the last pandemic."

On her outbound flight from Honolulu to San Francisco a month ago to see family, Paden said she saw at least three passengers wearing face masks.

"I was wondering what’s going on because it bothers me that I might get sick," Paden said.

Hawaii health officials rely on airline flight crews and federal Transportation Security Administration, customs and border protection agents to spot passengers at Honolulu Airport who may be sick while arriving or departing, Park said.

Once a patient is identified on an inbound flight by a crew member, the airport’s medical staff on the ground will keep everyone on board while they spend five to 10 minutes assessing the ill passenger, said Navy Cmdr. Tai-Ho Chen, quarantine medical officer for the Centers for Disease Control and Prevention who works out of Honolulu Airport.

All the ill passengers who have been asked to have their mouths swabbed for a sample to be tested have complied, Chen said, although he didn’t have a number of how many people have been swabbed.

And Whelen has been called out to the airport in the middle of the night to take samples back to the state laboratories on Waimano Home Road in Pearl City for testing.

The state laboratories had already developed partnerships with hospital, civilian and military labs to handle thousands of potential tests for a possible avian flu outbreak when the swine flu hit the islands in 2009.

While other states’ labs were swamped with tests for H1N1, the Health Department relied on doctors’ initial positive tests for influenza and then conducted further tests for H1N1 at the state laboratories.

"With the tidal wave of specimens coming in," Whelen said, "Hawaii responded to the H1N1 pandemic much better from a lab standpoint than many other states and state labs that were absolutely overwhelmed. It’s something we anticipated."

One of the primary purposes of the proposed $47.5 million Pacific Health Research Laboratory in Kalaeloa is to quickly turn around results if there is a suspected infectious disease outbreak. Project spokes­man Floyd Takeuchi said the closest lab currently able to handle a large-scale outbreak is in Colorado.

Tourists and returning residents sometimes board Hawaii-bound flights while feeling ill and try to avoid detection when they arrive in Honolulu, Park said.

"People are going to travel here no matter how sick they are," she said. "We are a vacation destination. People save their hard-earned money, sometimes their life’s savings, for a vacation to Hawaii. Are they going to say, ‘I need to reschedule,’ if they’re feeling under the weather? No. They’re going to travel while ill."

If they slip through Hono­lulu Airport with a highly infectious disease, Park has only five investigators for all of Oahu to track them down and account for everyone the patient has been in contact with.

In 2006, visitors from Asia brought a child through the airport who was diagnosed days later with mumps, Park said. The family had taken the child to their vacation condo, then contacted a local doctor who then called the Health Department, which sent an investigator and had the family quarantined, Park said.

"It is possible for travelers to clear through customs and be fine for a day or two and then start to come down ill," she said. "That’s what happened with this child and that’s what happened with the swine flu."

Tourists sometimes don’t want to bear the extra costs to extend their time in Hawaii to remain quarantined in their condos or hotel rooms — or pay the cost of rearranging flights to return home once they’re well.

So the Hawaii Tourism Authority has helped out some patients with their extended stays, Park said.

"We obviously don’t want them flying and exposing a whole new group of people," she said. "In most cases, we’ve not had a huge issue. But if we need to, we can notify the airlines to say, ‘This person is not allowed to fly because of public health issues.’"

Those who insist on flying while ill should wear a mask to be courteous to others and to reduce the spread of infection, Park said.

And if they arrive in Hawaii feeling sick, "don’t wait to go see the doctor," Park advises. "Give your doctor a fighting chance to help you."

Healthy passengers making the long trans-Pacific flights to the mainland, Asia and throughout the Pacific Rim can help themselves by getting lots of sleep before a flight and staying hydrated while en route, which keeps skin and mucus membranes moist and less prone to infection, Park said.

"Be aware," she said, "and be proactive for yourself and for your family."