The number of confirmed human cases leapt from just 11 in Indiana last week and 29 nationwide — including 12 in neighboring Ohio — but Indiana's Health Commissioner Greg Larkin said it was "not necessarily more contagious" than any other virus.
All of the cases in Indiana have been transmitted from hogs and pigs to people, mostly people handling the animals, Larkin said, and none directly from person to person.
"What we're seeing is a mild illness, not a severe illness," Larkin said in a telephone interview.
The symptoms are similar to those seen with seasonal flu and last three to eight days, he said. Symptoms include fever, cough, sore throat, runny nose, body aches, nausea and diarrhea, and may last anywhere from three to eight days.
The counties with confirmed cases stretch from northwestern Indiana to south-central Indiana: Bartholomew, Greene, Hamilton, Hendricks, Jackson, Jennings, Johnson, Kosciusko, LaPorte, Lawrence, Monroe, Morgan, Owen, Porter, Scott, Tipton, Washington, and White.
No cases have been reported in Marion County, where the Indiana State Fair began last week. Fair officials sent home most of the hogs in its swine barn Monday after six pigs in the 4-H show developed high fevers. The cause of the fevers has not been determined.
Larkin said it was not unusual for confirmed cases of a virus to grow so quickly. Once laboratory officials can confirm a virus is a certain type, the confirmation process goes more quickly, and as people become aware of the virus, more cases get reported to health officials.
"This has been very similar of any virus to when it first presented," Larkin said.
The Centers for Disease Control has been looking into reports from several states. A CDC spokesman on Wednesday said the agency is expecting to give updated national numbers this week.
Health officials are most concerned about whether the virus continues to spread among people and whether it becomes unusually deadly. So far, there's no evidence either has happened, health officials said.
Larkin said the virus cannot be transmitted by eating pork or pork products.
The state health department has sent advisories to local health providers asking them to send in samples from flu-like cases they encounter.
Last week, the department established a call center to answer the public's questions about the flu. The call center reachable at (877) 826-0011 is staffed from 8:15 a.m.-4:45 p.m. Monday through Friday. Information also can be found online at http://www.in.gov/isdh/25462.htm.
Associated Press writer Mike Stobbe in Atlanta contributed to this report.
Ken Kusmer can be reached at http://twitter.com/kkusmer