"What it comes back to is, What was the transmission route? Was it someone with poor hygiene? Was it a food product coming into Chi-Chi's? Hopefully we're going to nail that down pretty soon," said Richard McGarvey, spokesman for the state health department.
Initial interviews with outbreak victims led investigators to believe the contamination was likely caused by a food-worker rather than food brought into the restaurant. Yesterday that wasn't so certain.
Dr. Bruce Dixon, director of the Allegheny County Health Department, said the growing tally of confirmed cases made it hard for him to believe that just one worker handling individual meals could be responsible. Dixon is not involved in the investigation but is well versed in public health issues.
"I think there was diffuse contamination and I would think, as a result of that, that you probably have a foodstuff that was probably contaminated," rather than a single individual repeatedly contaminating food, said Dixon.
Nonetheless, Dixon acknowledged that one sick employee could have contaminated food that was then stored and served over an extended period of time. Salads prepared in the morning and served over the course of a day or several days could be one scenario, he said.
Ice is another suspect. A worker with the disease who failed to wash his hands properly scoops out some ice with his hands, leaving microscopic bits of fecal matter in the machine.
Ice machines have been identified as the source of previous outbreaks, said Dr. Andre Weltman, a public health physician with the state Department of Health. "This is a virus that is pretty hardy, so it is possible for a surface to become contaminated."
Not much contamination is needed. It takes only 10 to 100 virus particles to spread hepatitis A, according to Dixon, while it takes several hundred virus particles to spread some infectious diseases.
Yet another possibility is that several employees were infectious and didn't know it. The greatest danger of spreading the disease occurs during the middle of the virus's 28-day incubation period, well before symptoms appear, according to the U.S. Food and Drug Administration.
In interviews last week, Weltman said investigators had a variety of reasons for thinking the outbreak was not caused by a contaminated food brought into the restaurant.
First, there was no clear evidence a single item had been consumed by all those who are sick. Second, there have been no hepatitis cases linked to other Chi-Chi's restaurants, which likely share common food distributors, he said.
"We may never solve this," Weltman said then. "It's possible we'll never be able to figure this out and it's possible we'll never be able to exclude an imported food item."
Experience with other outbreaks shows how poor worker hygiene can cause contamination.
Weltman investigated a hepatitis A outbreak in New York in the mid-1990s in which a pastry maker failed to wash hands after going to the bathroom. The worker then applied a sugar glaze to doughnuts, some of which were sold immediately while others were frozen and sold later in the month.
"When someone uses the toilet and they have diarrhea, specifically from hepatitis A, they really do put out a lot of virus," Weltman said. "Unfortunately, it's fairly easy to get contamination of the hands or other surfaces."
Fecal matter can wind up under fingernails and on hands. The amount could be microscopic and not apparent to the naked eye, yet it's still enough to spread disease, Dixon said.
"On a surface, the virus probably can still be viable for a couple of days, so long as it's in the right setting and it doesn't get cooked," said Dr. Tony Fiore, a medical epidemiologist with the U.S. Centers for Disease Control and Prevention. "It doesn't require a lot of virus to make someone ill."
Having said all this, public health officials point out that hepatitis A is relatively rare, particularly in the eastern United States. There are about 23,000 cases each year, according to the U.S. Food and Drug Administration.
Between 1987 and 1997, the average rate of cases in Pennsylvania was 5.48 per 100,000 people. In Beaver County, the rate was even lower -- slightly more than one case for every 100,000 residents.
Representatives for Chi-Chi's declined to comment yesterday. The company, based in Louisville, Ky., planned a news conference for today.
The outbreak has claimed one life. About 150 people attended private funeral services yesterday for 38-year-old Jeff Cook of Aliquippa. Cook, who became ill after his family ate at the Chi-Chi's Restaurant in early October, died of liver failure Friday following a transplant.
Hepatitis A generally causes flu-like symptoms that can last up to two months, but generally doesn't cause permanent liver damage, unless the person already has liver problems or an immune deficiency problem.
The University of Pittsburgh Medical Center yesterday said four people were in fair condition and two remained in critical condition for illnesses tied to the outbreak.