Multistate Outbreak of Salmonella Kiambu Infections Linked to Yellow Maradol Papayas

Multistate Outbreak of Salmonella Kiambu Infections Linked to Yellow Maradol Papayas

Courtesy of the CDC

The Centers for Disease Control and Prevention (CDC), public health and regulatory officials in several states, and the U.S. Food and Drug Administration (FDA) are investigating a multistate outbreak of Salmonella Kiambu infections.

Public health investigators are using the PulseNet system to identify illnesses that may be part of this outbreak. PulseNet is the national subtyping network of public health and food regulatory agency laboratories coordinated by CDC. DNA fingerprinting is performed on Salmonella bacteria isolated from ill people by using techniques called pulsed-field gel electrophoresis (PFGE) and whole genome sequencing (WGS). CDC PulseNet manages a national database of these DNA fingerprints to identify possible outbreaks. WGS gives a more detailed DNA fingerprint than PFGE.

As of July 21, 2017, 47 people infected with the outbreak strain of Salmonella Kiambu have been reported from 12 states. A list of the states and the number of cases in each can be found on the Case Count Map page. WGS showed that isolates from people infected with Salmonella Kiambu are closely related genetically. This close genetic relationship means that people in this outbreak are more likely to share a common source of infection.

Illnesses started on dates ranging from May 17, 2017 to June 28, 2017. Ill people range in age from less than 1 year to 95, with a median age of 27. Among ill people, 67 percent are female. Among 31 people with available information, 18 (58 percent) are of Hispanic ethnicity. Among 33 people with available information, 12 (36 percent) report being hospitalized. One death was reported from New York City.

This outbreak can be illustrated with a chart showing the number of people who became ill each day. This chart is called an epidemic curve or epi curve. Illnesses that occurred after June 23, 2017 might not be reported yet due to the time it takes between when a person becomes ill and when the illness is reported. This takes an average of two to four weeks.

Epidemiologic and laboratory evidence collected to date indicate that yellow Maradol papayas are a likely source of this multistate outbreak. This investigation is ongoing.

In interviews, ill people answered questions about the foods they ate and other exposures in the week before they became ill. Eleven (44 percent) of 25 people interviewed reported eating papayas. This proportion was significantly higher than results from a survey of healthy Hispanic people in which 16 percent reported eating papayas in the months of May and June in the week before they were interviewed.

An illness cluster in Maryland was identified. An illness cluster is defined as two or more people who do not live in the same household who report eating at the same restaurant location, attending a common event, or shopping at the same location of a grocery store in the week before becoming ill. In Maryland, several ill people reported eating papayas purchased from the same location of a grocery store. Salmonella Kiambu and Salmonella Thompson were isolated from samples collected from ill people. Investigating illness clusters provides critical clues about the source of an outbreak. If several unrelated ill people ate or shopped at the same location of a restaurant or store within several days of each other, it suggests that the contaminated food item was served or sold there.

The Maryland Department of Health collected papayas from the grocery store associated with the illness cluster to test for Salmonella. One sample yielded the outbreak strain of Salmonella Kiambu and another sample yielded Salmonella Thompson. Both samples were from yellow Maradol papayas. WGS showed that the Salmonella Kiambu papaya isolate is closely related genetically to the Salmonella Kiambu isolates from ill people. This result provides more evidence that people in this outbreak got sick from eating contaminated yellow Maradol papayas. CDC is working to collect additional information to determine whether the recent Salmonella Thompson illness in Maryland is part of this multistate outbreak.

Based on the available evidence, CDC recommends that consumers not eat, restaurants not serve, and retailers not sell yellow Maradol papayas until the agency learns more. CDC and state and local public health partners are continuing laboratory surveillance through PulseNet to identify additional ill people and to interview them. Further investigation is under way to determine the point in the supply chain where the papayas were contaminated.

Source: CDC

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