Ping! And so it begins.

A ping triggered by a positive hepatitis A result is most often how the state Department of Health learns of new cases in the latest outbreak of the viral infection. That alert, with only a name attached to it, comes through the DOH electronic laboratory reporting system and sets off a labor-intensive search for information.

Health officials must track down the doctor who ordered the test and the patient’s contact information. Then there’s a step-by-step process — including interviews, data input, analyses and site visits — that feeds data into a full-blown investigation to pinpoint the source of the state’s worst outbreak of hepatitis A in more than a decade.

Last week, the number of confirmed cases of hepatitis A stood at 135, up 45 percent from July 27 when the count was 93. At least one, possibly two, are secondary cases, meaning the viral infection was passed on through a primary source, said Dr. Sarah Park, state epidemiologist, who is leading the investigation. It is critical to “cut the chain of transmission,” she said.

The quest to determine the source is exhaustive — as well as exhausting for investigators.

“It just gets very tedious. It takes a lot of patience, a lot of hours,” Park said, noting investigators are following up on some solid leads — though none that she can share publicly.

On Monday, Park and DOH Director Virginia Pressler will provide lawmakers an update on the outbreak during an informational briefing at the state Capitol. The outbreak is unusual; Hawaii had an average of 10 hepatitis A cases reported annually over the past 10 years.

The viral liver infection spreads through fecal matter that contaminates food or drink, which is then consumed. It is also spread through close personal contact. Preventative measures include vaccination, properly cooking food and thorough hand-washing.

The latest wave of hepatitis A cases — 42 of the 135 — in Hawaii’s current outbreak involved adults with onset of illness ranging from June 12 to July 24. One challenge is the virus’ long incubation period, which can be from 15 to 50 days after exposure.

And that makes it extremely difficult for investigators such as Cathy Wu, a DOH epidemiological specialist for 10 years.

Once the department receives a new case, the detective work begins. Wu said that she and other investigators review the clinical information, which often requires calls to a doctor’s office or hospital’s infection control office for clarification or more info. When the case is confirmed, the patient is contacted for an interview — most times it is done over the phone using a 15-page questionnaire, Wu said.

Wu, who estimates she has interviewed about 25 hepatitis A patients in the recent outbreak, said the questionnaire seeks demographic information, clinical info and tackles risk factors and exposures. The last part of the questionnaire can be the most daunting as investigators seek a detailed food history from the patient, trying to gather specific information on the patient’s diet stretching back weeks, Wu said.

“That’s one of the challenges — the biggest challenge for us. … When I ask the patient, they will tell you, ‘I don’t even know what I ate yesterday,” Wu said. All told, the interviews usually last about 45 minutes. It requires a lot of talking, Wu said, and at times it takes leaving multiple voicemail messages before she is able to interview a patient.

“Some of them are really trying to help and trying to get as much information as possible … some are tired, some say ‘no, no, no,’ ” Wu said. After handwriting a patient’s answers, she later enters them into a computer database.

To fill in blanks, investigators ask for shopper-card numbers and other documentation to gain access to what the patients purchased or where they have shopped or dined.

That bank of information then goes to another set of experts who start to tabulate patient responses. “It’s essentially a lot of data cleaning,” Park said, and then analysts attempt to find common links. A statistician also will do more complex biostatistical analyses, she said.

The goal is to find commonalities in exposures, perhaps a link through consumption of a certain food.

The research “is starting to help focus in on a few lines of theories (but) it’s not something that jumps right out at us,” Park said. “It takes a lot of good, smart humans cleaning the data, putting two and two together, working as a team, talking to each other.”

There is no glamour in this kind of work, Park said. This is not like an episode of “CSI,” where the culprit is identified within a TV hour.

Containing the spread is key. A few of the patients work in the food service industry, which prompted yet another layer of inspection and investigation involving DOH environmental health workers.

For instance, among the confirmed cases were individuals who worked at Taco Bell in Waipio, Baskin Robbins in Waikele, a Chili’s in Kapolei and Costco Hawaii Kai’s bakery.

When a food handler has a positive hepatitis A diagnosis, an inspector is sent to the establishment. The infected employee must be kept away until given a medical clearance and inspectors monitor the operation for safe food handling and proper hand washing, said Peter Oshiro, DOH environmental health program manager.

“These are purely preventable diseases if everyone handwashed properly,” Oshiro said.

Inspectors chase down invoices to turn over to Park’s investigators who check to see which distributors are used and what products are brought into the business. “It’s super invasive, but our local people have been very cooperative … (providing) hundreds and hundreds of pages of invoices, receipts,” Oshiro said.

“It goes so deep. A lot of it is manual entry into computer. What they are looking for are commonalities. Where they ate, which ones are in common, which ones are not. They are doing a massive amount of work,” Oshiro said.

Inspectors such as Wu then have to contact food handlers at the affected establishments to tell them they must get tested for hepatitis A or show proof of a hepatitis A vaccination before they can return to work.

“As soon as the outbreak is identified, you basically just follow the program manual,” Wu said.

And despite DOH’s due diligence, there is still a good chance the source will never be found.

Vivek Nerurkar, chair of the University of Hawaii’s Department of Tropical Medicine, Medical Microbiology and Pharmacology, said it’s quite common that the source is never pinpointed.

He compared it to FBI cold cases. “After doing a lot of investigation you might end up with nothing conclusive,” Nerurkar said. “Foodborne contaminations are always difficult to pinpoint. Oral-fecal (types) are more difficult.”

While finding the source is the goal, preventing future cases is just as important, he said.

Inspectors, like Wu, must closely monitor household contacts of patients and make sure they receive vaccinations since the infection can be spread through food service or sharing. It’s also why the department has been vigilant about getting word to coworkers and potential customers who might be affected by the diagnosed food handlers.

What needs to happen, Park said, is more doctors must contact the Health Department when they have patients exhibiting hepatitis A symptoms — fever, nausea, vomiting, fatigue, joint and abdominal pain, dark urine and jaundice. Receiving an alert from a doctor about a patient with symptoms allows the department to more quickly set in motion its probe, as opposed to reacting to an electronic ping from a positive lab test result.

The lag time from the lab work can be several days to a week — precious time in which the department could be warning the patient not to share or serve food. “The longer it takes (to identify the patient), the harder it is to cut that chain of transmission,” Park said.