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Environmental factors may influence Kawasaki disease incidence
Weather patterns in southern California may impact the distribution of Kawasaki disease, according to research published in Scientific Reports.
Jane C. Burns, MD, director of the Kawasaki Disease Research Center at the University of California, San Diego School of Medicine, and colleagues hypothesized that there are potentially multiple triggers that can cause the condition such as genetic predisposition, as well as wind patterns and other environmental exposures.
“Researchers in Chicago are working on the concept that Kawasaki disease is caused by a novel virus and a single agent,” Burns told Infectious Diseases in Children. “Data from this paper and other work that we have done, as well from as researchers in Japan, suggest that there might be more than one trigger for the disease. There is not an infinite number, but there are different triggers that result in a slightly different flavor of immune response.”
Burns and colleagues noted that Kawasaki disease is relatively rare in American children, with fewer than 6,000 developing the condition annually. However, in San Diego County, the incidence Kawasaki disease has risen in children aged younger than 5 years — from 10 per 100,000 in the 1990s to 25.5 per 100,000 in 2006-2015. It is currently unclear what etiologic agent triggers Kawasaki disease, and “extensive searches for an infectious agent have not yielded a consistent pathogen,” the researchers wrote.
According to Burns and colleagues, 1,164 patients with Kawasaki disease were treated at Rady Children’s Hospital San Diego during a 15-year period. The researchers observed a seasonal trend in cases, peaking from January through March and peaking again to a lesser degree in June.
The researchers also observed “strongly significant” regional air temperature anomalies and large-scale wind patterns that contributed to the incidence of disease. Burns said it is possible that a trigger of the disease could be carried by the wind.
Additionally, when researchers analyzed patients’ gene expressions, they found distinct clusters of patients. Children in each cluster had similar ages and measures of inflammation.
“When we went back and questioned whether patients were clinically different from each other, we found [three clusters of disease, and] one of the three groups had much higher inflammation,” Burns said. “That was the lightbulb moment for us where we realized that these patients cluster in time and space, but there is a sporadic background of patients. There were only 39 clusters, but the clusters had at least five or more patients in them within a period of 7 days.”
Burns said that until there is a clear answer as to why these cases occur, all hypotheses are viable. Currently, a team of climate scientists are investigating the effects of wind and climate patterns on the development of Kawasaki disease on a cluster-by-cluster basis.
Another possibility, according to Burns, is that the intensity of the unknown exposure may contribute to the clusters of disease. She said it is possible that some children had greater exposure to a trigger, whereas others did not. These exposures could occur through the upper respiratory tract and trigger a genetic response.
She added that a “fruitful area of research” is in Japan, where there are more cases of Kawasaki disease and the seasonal peak in incidence has been clearly defined.
“We are collaborating with climate scientists there to try to understand what the children’s exposures might be,” she said. “Previous data from our climate science group suggest that it is something in the wind carried in from northeastern China. Our climate team is working with Chinese scientists in the potential source region to try to do aerosol analyses to see if we can identify something that could be carried in the wind that blows over to Japan and triggers children there.” – by Katherine Bortz
Disclosure: Burns reports no relevant financial disclosures.
