INDIANAPOLIS (AP) — A federal shipment of enough antiviral drugs to treat 238,000 people arrived Wednesday in Indiana as the state's health commissioner crisscrossed the state, telling residents at each stop that diligence is key to preventing a swine flu outbreak.

The shipment put Indiana among the first wave of states and cities - New York state and New York City were the other recipients - to get extra antiviral medication from a federal stockpile as officials brace for a possible wide outbreak.

State officials plan to distribute the new drugs on Thursday by dispatching a portion to each of Indiana's 92 county health departments.

The new virus' emerging threat, meanwhile, affected at least two Indiana colleges' study programs in Mexico, where swine flu is suspected in the deaths of about 160 people.

Indiana University suspended all of its Mexican summer study programs, a move that affects 50 to 60 IU students and 20 high school students. And the University of Notre Dame said eight students studying in Mexico will return to the U.S. early, arriving home by the end of the week.

As fears mounted that the swine flu virus could spark a global pandemic, state health officials awaited test results from the Centers for Disease Control and Prevention on viral samples taken from about 30 Indiana residents suspected of contracting the disease.

As of Wednesday evening, the state said it had received only one test result from CDC - a confirmed swine flu case in a Notre Dame student who's already recovered from the illness and who is so far Indiana's only case of the disease.

Despite state officials' comments, officials in Marion County - the state's most populous county - said at a Wednesday news conference that the CDC had informed them that two of four viral samples collected in the county were negative for swine flu.

Results on the two other samples are still pending, said John Althardt, a spokesman for the Marion County Health Department.

Elizabeth Hart, a spokeswoman for the Indiana State Department of Health, said the state agency had received only one result from the CDC - the result on the Notre Dame student.

She said the state is "anxiously awaiting" the remaining CDC test results but is aware the federal agency's laboratories are burdened by large numbers of samples from many states.

"There really is no timeline - it's as soon as they can get them. So we're all standing by, waiting in line like everyone else," Hart said.

State Health Commissioner Dr. Judy Monroe traveled to Jeffersonville, Fort Wayne, South Bend and Gary on Wednesday, stressing at each stop the need for the public to practice commonsense hygiene, including frequent hand-washing to prevent the spread of the virus.

Monroe is also urging Indiana residents who become ill with flu-like symptoms that include a fever of more than 100 degrees Fahrenheit, headaches, sore throat or body aches to stay at home and remain there for at least 24 hours after their flu symptoms have ended.

With the addition of Wednesday's shipment of antiviral drugs, Indiana now has enough such medication to treat 889,000 people for the new virus - or about 14 percent of the state's 6.3 million residents.

By Sunday, the federal government said that all states will have their share of enough medication to treat 11 million people - just in case the swine flu takes off.

Hart said that once the drug shipments to the counties are complete, the state health department will still have on hand enough antiviral medication to treat 651,000 people.

At Notre Dame, health officials working with the state had not yet determined how the student at the South Bend campus had become infected with the virus, said spokesman Dennis Brown. The student had not recently visited Mexico, and it's unclear if the student had been in contact with someone who had recently returned from Mexico, he said.