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RALEIGH North Carolina public health officials today said that they have additional cases of possible E. coli under investigation. Most of them, however, are under investigation and have not been confirmed.
When you really look hard for E. coli cases as part of an outbreak investigation, you are always going to find them, said State Epidemiologist Dr. Jeff Engel. Increased surveillance means that you will find unrelated cases that would have gone unnoticed or undiagnosed without the attention that comes with a potential outbreak. It also means that you will find cases that are related to the outbreak, but hadnt been included before.
Public health officials continue to stress prevention of the disease. E. coli is found in about 10 percent of farm animals intestines, said Engel. Since the animals have no symptoms, we need to take actions to stop potential spread of the disease. Always thoroughly wash your hands after petting any animal. People also need to be aware that this disease can be spread through ingestion of contaminated food. Thoroughly cooking hamburger and washing vegetables also helps to prevent the disease.
Engel also noted that there have been no reported cases of secondary infection. We havent found any cases of human-to-human transmission, he said. The cases that are related to the outbreak appear to be primary infections.
The best way to reduce the risk of getting E. coli from another person is thorough hand-washing, he added. Child care workers and others who work with children need to make sure that everyone children and workers wash their hands thoroughly. If a child care worker notices a child who appears to have diarrhea, they should immediately contact the parents and their local health department.
In most cases a person with E. coli may be ill with diarrhea for a few days followed by improvement. However, the risk of transmitting the infection may continue for up to three weeks because the bacterium is still found in bowel movements. Coming in contact with even small amounts of harmful types of E. coli can cause illness. For these reasons, it is very important that anyone who is recovering from stomach illness continues to carefully wash their hands.
Although officials are still not ready to give a definite cause for this outbreak, genetic fingerprinting of the strain of E. coli along with the public health investigation is pointing to one outbreak that appears to center around contact at the state fair.
So far, genetic fingerprinting has been done on several of the cases. Five of them had an identical strain of E. coli and had exposure at the state fair. That puts us closer to identifying the source of the outbreak, said Engel. We will run genetic fingerprints on the other confirmed cases and positive environmental samples and that should give us more evidence on whether to link attendance at the state fair petting zoo to the outbreak. From a public health viewpoint, we want to get as much information on any outbreak so that we can use that information to prevent future such occurrences.
The genetic fingerprinting also showed how the epidemiologic investigation of an outbreak can pick up additional cases unrelated to the outbreak. Two Mecklenburg patients had the same strain of E. coli, but it was different from the five genetically related cases. Those two patients also got sick before the fair and never attended the fair.
This is the kind of thing you find during an investigation, Engel said. These two cases are related to each other, but they arent related to the other five cases. We are no longer investigating them as part of this outbreak, but Mecklenburg County health authorities are looking into those cases to see how they are related to each other.
These details have led public health investigators to focus their attention on a particular period of time that coincides more closely with possible state fair exposure. Authorities are now focusing on anyone who has been in North Carolina since Oct. 8 and had the onset of diarrhea (defined as three or more loose stools in a 24-hour period for two or more days) that occurred after Oct. 14. Defining a time period, a place and specific symptoms is used to build a case definition that helps sort out reports during an outbreak investigation. A change in case definition can also lead authorities to drop cases that had been potentially considered as part of an outbreak. For instance, the cases detailed above in Mecklenburg County are no longer considered part of this outbreak.
Authorities are considering 20 confirmed cases as potentially part of the outbreak, but further investigation may find that some of those cases are unrelated to the outbreak. Seventeen of the 20 cases had visited the state fair, with exposure to animals reported by most. It isnt yet known whether the other three had visited the state fair. Another 39 possible cases are under review, but have not been confirmed as E. coli. infection. Continued epidemiological investigation, which will include genetic fingerprinting of confirmed cases, will allow investigators to determine how many cases may be associated with each other and whether those cases are indeed associated with attendance at the state fair.
The following table gives the number of confirmed cases by county that may be potentially associated with this outbreak. Note that these numbers have changed from what was previously reported: thats because of the change in case definition discussed above.
County Number with Positive Lab Tests for E.coli
Source: North Carolina Department of Health and Human Services