At least 31 cases of Hepatitis A infection have been confirmed on Oahu, according to a July 6 announcement from the Hawaii State Department of Health. That’s up 19 from the initial case count of 12 reported July 1. Six people have been hospitalized.

Illness onset ranged from June 16 to June 27, according to the health department. The source of the virus is likely food- or water-related, but is still under investigation. Ahi poke, a kind of raw tuna salad, is one suspect food item, according to a report by a Honolulu-based television and internet news outlet. Health department staff worked through the Fourth of July weekend to interview the newly confirmed patients to try to pinpoint the cause of their illnesses. “Identifying the source of infection is a challenge,” said State Epidemiologist Dr. Sarah Park. “Hepatitis A has a long incubation period lasting anywhere from two weeks to as long as 50 days. Accurately recalling all of the foods consumed and locations visited during the period when infection could have taken place is challenging for many, especially those who are still feeling ill.” On Thursday, Park said this is an especially frustrating outbreak because those sickened did not eat the same food items or even at the same places. As a result, the source of the problem is proving more elusive than usual. “We’ve had cases who stressed they definitely didn’t have ahi poke, so we’re in the hypothesis-generating stage of trying to look at the cases in 10 different ways. It is interesting to us that we haven’t been able to identify a cluster within a cluster, so to speak,” she said. Park said Hawaii health officials would like to be able to link together 75 to 80 percent of the confirmed Hepatitis A cases and then find a way to “rope in all the others.” Meanwhile, she has been cautioning people not to jump to conclusions about the source of the virus in order to avoid tainting the ongoing epidemiological investigation.

“We haven’t determined a food source. To say that’s it, it’s way too early to say. It could be water, it could be anything you drank,” she said. People infected with the Hepatitis A virus are most contagious during the week before the symptoms start until at least a week after the start of the first symptoms. They may not feel ill at that point, so health officials are concerned about the virus being spread to others, including household members and close contacts of those sickened. Hepatitis A is found in the stool of people with the infection and is usually spread by eating contaminated food or drinking contaminated water. The virus can also be spread through close personal or sexual contact. Hepatitis A vaccine or immune globulin — a substance made from human blood plasma that contains antibodies to protect the body against diseases — that is administered within the first two weeks after exposure may provide some protection against the disease. “Hepatitis A infection is a vaccine-preventable disease, and fortunately, most children and adolescents have been vaccinated as part of routine childhood vaccination recommendations,” said Hawaii Health Director Dr. Virginia Pressler. “However, many adults have not been vaccinated and remain susceptible.” Unvaccinated individuals recently exposed to the virus are encouraged to talk to their health care providers about preventive measures. Health officials encourage the public to review their immunization record and talk to their doctors about vaccination. A list of Hawaii pharmacies providing adult vaccinations is available online, or by calling the Aloha United Way information and referral line at 2-1-1. Park said that while Hawaii doesn’t yet have a universal vaccination registration system, anecdotal information indicates that the current outbreak has prompted some residents to ask about getting Hepatitis A vaccinations. “We have heard more questions about it, but I hope the message is getting out there and people are getting it,” she said. “We are such a global village now. When you think how the Hepatitis A vaccine was brought on initially, it was only recommended for high-risk individuals. Now it’s universal and there is no such thing as a high-risk population.” While vaccination provides the best protection from Hepatitis A infection, other ways to help prevent the spread of the virus include frequent hand washing with soap and warm water, especially after using the bathroom or changing a diaper, and before preparing food. Additional information about Hepatitis A can be found on the Department of Health website. (To sign up for a free subscription to Food Safety News, click here.)