Federal health officials are investigating more than 200 cases of students who developed an acute respiratory illness that they suspect is histoplasmosis.

The students are from 37 colleges and universities in 18 states, but nearly all of them had one thing in common–they vacationed in Acapulco during March and stayed at or visited the Calinda Beach Hotel there, according to the federal Centers for Disease Control and Prevention.

The first outbreak was picked up by an alert student health physician late last month at Villanova, where 29 students got sick about two weeks after returning home. Similar cases have been identified from Massachusetts to Missouri. Locally, some students at Rutgers University, Muhlenberg College in Allentown and Pennsylvania State University fell ill.

Histoplasmosis is a fungal disease that primarily affects the lungs and can be deadly in people with other health problems. The fungal spores involved thrive in dirt rich in bird and bat droppings and can be breathed in when soil is disturbed.

“There was some construction going on around the hotel,” said Dr. Rana Hajjeh, a CDC epidemiologist in Atlanta, who is heading the investigation. But she said it would be premature to conclude the hotel site was the source of the infection because “the hotel is not the only link that is common.”

She said there was also construction near certain bars and nightclubs the students tended to frequent.

Hajjeh said CDC officials are in consultation with the Mexico Ministry of Health, which is conducting its own investigation. The Calinda Beach Hotel has not been shut down, she said.

While it suspects histoplasmosis, the CDC so far has tentatively confirmed only one of the more than 200 cases under investigation, Hajjeh said. That was from a lung biopsy done on a student at Washington University in St. Louis.

Dr. Richard Pacropis, an internal medicine specialist who directs student health at Villanova, set off a national alert among college campuses after he figured out what was likely bringing so many students into his infirmary.

On March 28, a student came in with a high fever, muscle aches, chest pain, dry coughing and weakness, and she was soon followed by others with similar symptoms.

“We had 29 students over a four- to five-day period,” said Pacropis. Six of them ended up at Bryn Mawr Hospital, where Pacropis is on staff. In taking medical histories on the students, he learned that all of them had spent the March 3-11 spring break in Acapulco.

They didn’t appear to have the more predictable illnesses, such as flu or mononucleosis. But chest X-rays revealed a fungal infection of the lungs. Because the infection has a 2 to 21/2- week incubation period, the students had felt fine when they first came back to campus.

Carissa Giardino, 21, a Villanova senior from Doylestown, Pa., said she was among a group of 30 Villanova women who spent about $850 each for a package deal that included airfare and a week’s stay at the Calinda Beach Hotel.

After getting back to classes, she began to experience a high fever, muscle aches, fatigue “and a lot of soreness in the chest; it hurt to breathe normally.”

When she didn’t get better after a week and heard of a friend who had a suspected case of histoplasmosis, she went to the emergency room at Bryn Mawr Hospital.

The sickness wiped her out. “I didn’t do anything but go to classes for two weeks,” Giardino said.

Pacropis said the most seriously ill students were given a 28-day course of anti-fungal medicine. All 29 students are now recovered.

Pacropis reported the cases of suspected histoplasmosis to the Pennsylvania Health Department, which entered the investigation and, in turn, alerted the CDC.

From his students, he learned the names of other colleges with students staying at the same hotel and took it upon himself to alert their medical directors. He said he has received calls from around the country.

One Penn State student who stayed at the Calinda Beach Hotel is now being evaluated for histoplasmosis, according to a university spokesperson.

Sam Miranda, head of student health at Muhlenberg, said his center has identified seven possible cases among students who spent spring break in Acapulco. All are back to good health.

Hajjeh, of the CDC, said histoplasmosis is a disease that routinely pops up around the country, particularly in areas such as the Ohio and Mississippi River valleys, where the soil is rich in the fungus.

“We’ve had a lot of outbreaks,” she said. “But this is the first one of such multi-state magnitude.”