State health officials have confirmed nine cases of the same strain of E. coli on Oahu this year.
In 2012, there were 10 confirmed cases of E. coli. The state has launched a full investigation.
"It's a definite bump, so it is something we are very concerned about," said Michelle Nakata of the Department of Health Disease Investigation Branch.
State health officials are asking health care providers to keep an eye out for possible E. coli infections in their patients.
The first cases were reported for Feb. 19. Six involved children under the age of 10. Four cases were severe enough to require hospitalization. Only one person remains hospitalized and is improving.
All cases are Oahu residents, except for one visitor to the islands. But so far, that is where the similarities in this outbreak stop.
"So far, unfortunately, there's nothing in common -- no common activity, no common food items, not even common restaurant among the cases so that's what's been complicated," said Nakata.
E. coli can be transmitted usually through beef and through contamination of food sources, including vegetables, and through contaminated food handlers.
Nakata says health department investigators are now researching the shopping habits of the victims, as well as the restaurants where they may have eaten within the weeks prior to getting an E. coli confirmation.
The sanitation branch is actually reaching out to the restaurants in an effort to trace back where they got the ingredients used to make their meals to see if there is anything common.
This particular strain of E. coli O157 is not common, but it is among the more severe strains.
Symptoms include cramping -- severe enough the parents say the children crouched down because of the pain.
Diarrhea is also another symptom, possibly containing blood. If you have these symptoms you should see your doctor.
Two other E. coli cases have been confirmed, but health department officials say they don't have the same "fingerprint" as those in the outbreak, or cluster, as they call it.
One of the best ways to avoid E. coli is safe food handling. The state Department of Health has a web page on infectious diseases where there is a link to the ways you can keep your family safe from food poisoning.