Part of a series investigating the complex linkages between human, animal and environmental health: The Infection Loop.
Dr. Jane C. Burns always takes her vacation in September and October. That's when, she says, there is a "lull in the action."
By action, she means the influx of children with Kawasaki disease that she has come to expect during summer and winter months. Similar seasonal patterns are seen in other parts of the world, but no one has been able to explain why.
Now Burns and her colleagues think they may have found an important clue -- blowing in the wind. Despite 50 years of research, the underlying cause of Kawasaki, a rare condition that involves the inflammation of blood vessels, remains unknown.
The interdisciplinary team of doctors and climatologists has linked large-scale wind patterns originating in central Asia to fluctuations in cases of the serious and sometimes fatal disease in Japan, San Diego and Hawaii. Their findings, detailed in the journal Nature's Scientific Reports on Thursday, suggest that when these particular wind currents reverse -- sweeping in from the south, in the case of Japan -- the number of Kawasaki cases drop. A close look at data from these three regions found no associations with other environmental factors such as precipitation, temperature or dew point.
"If the winds blow in one direction, there is Kawasaki; if winds blow in the other, there is no Kawasaki. It's very dramatic." says Burns, a professor of pediatrics and director of the Kawasaki Disease Research Center at the University of California, San Diego and Rady Children's Hospital.
Researchers are now looking at dust samples collected from winds over Japan in hopes of determining what virus, bacteria, fungi or other contagion -- live or inert -- ultimately triggers Kawasaki disease. And until that mystery is solved, no one can be certain of the wind's true role.
If the Kawakasi agent does, in fact, traverse great distances by wind, it would be the first known human infectious disease agent to do so. Dust plumes have been known to travel internationally. And some pathogens of plants and animals such as European livestock Foot and Mouth Disease and African Swine Fever can blow around, but only over relatively short distances, said Guy Hendrickx, managing director of Avia-GIS, a Belgian company specializing in spatial information for health and agriculture research. His own research has found that insects carrying Bluetongue virus will fly with the wind over hundreds of miles -- yet still not at the same high altitude and long distance suggested in the new Kawasaki research.
"Traveling with the aid of tropospheric winds should not be a problem for fungi, bacteria or even small cryptogams or other animals," says Jesus Munoz Fuente, a scientist at Real Jardin Botanico in Spain, suggesting the creatures can survive the flight by protecting their DNA from UV rays with other binding substances -- they can even survive with almost no water.
Some experts, however, are more skeptical. "I have never heard of such a close association between long-distance dispersal over oceans and outbreak of a human disease," says Christopher Mundt, a professor of plant pathology at Oregon State University. "This is more likely to happen with plant pathogens, but even there it seems to be somewhat rare and not something that happens on a regular basis." The correlations, he says, may have nothing to do with an agent being transported on the wind, but rather to something else associated with wind patterns.
Reported cases of Kawasaki disease are increasingly common in many parts of the world, particularly in Japan, where one out of 185 children will develop the disease before age 10. More than 12,000 cases have been reported in the country over the last year. Burns has also seen rising numbers in her San Diego clinic, although a growing awareness of the disease may be partially responsible. About 4,000 cases are reported in the U.S. each year, according to the American Heart Association.
In general, the disease is less recognizable outside of Japan and often mistaken for an inconsequential viral infection. Symptoms typically disappear on their own within a couple weeks. If not treated early, however, Kawasaki can cause irreversible heart damage. Burns recommends that parents consult a pediatrician if their child's fever lasts for at least five days and is accompanied by a rash, red eyes and red lips.
"This is a very insidious disease," says Burns. "The heart damage is silent. You have no way to know just looking at the child, but then in the child's 20s or 30s, they may present with a heart attack due to damage to arteries that happened during childhood."
In fact, she suggests that Kawasaki might be behind a number of the tragic heart-related deaths of young athletes. Only children with a genetic predisposition will get the disease, adds Burns, noting that Asian and African Americans have an increased susceptibility compared to other groups.
The ability to predict potential outbreaks of disease based on wind patterns, even without knowing nature of agent, has the potential to save lives, suggests Xavier Rodo, director of the Institut Catala de Ciencies del Clima in Catalunya, Spain, and lead author on the new paper.
Still, the lack of a known cause for the disease continues to be a major obstacle in disease prevention and treatment. If you don't know what you're looking for, it can be hard to find it, experts note. The key problem: Like other autoimmune diseases, the causative agent need not be present when symptoms appear. So researchers are forced to look further upstream -- as Burns and her team are currently doing.
"If there is a viral cause, one reason why it hasn't been identified to date is that we strongly suspect it is a virus in some new viral family that has not been discovered," says Dr. Anne Rowley, a leading expert in Kawasaki disease at Northwestern University Feinberg School of Medicine in Chicago. Her own research has found strong evidence to suggest a virus may be to blame.
So the hunt for the unknown continues. In March, researchers flew strategic sorties miles above Japan in the direction of the wind currents thought to be carrying the responsible agent. Ian Lipkin, a internationally recognized "virus hunter" at Columbia University in New York City, has begun analyzing dust samples collected by the specially designed filters in hopes of identifying candidate pathogens.
"There is a precedent for it, at least in the plant and animal world," he says. "And in science, anything is possible."