The story of a rare heart condition in children shows us that a better understanding of the relationship between climate and disease is more important than ever. Studies carried out in Japan, where the highest incidence of this disease was
first observed, indicate that there may be something carried by the wind that causes this condition.
In 1967, a Japanese paediatrician named Dr. Tomisaku Kawasaki observed a strange condition in children, which he referred to as a ‘febrile mucocutaneous lymph node syndrome.’ He reported 50 cases of a syndrome that did not fit in with the
usual diagnosis previously reported.
Kawasaki disease can cause a dramatic immunological reaction in children. It was first observed in Japan, where the highest number of cases occur worldwide. | Alexander Schimmeck / Unsplash
The condition is now known as Kawasaki disease (KD) and the main symptoms include a high fever, neck lymph nodes, conjunctivitis, a rash with cracking of the skin and damage to the coronary arteries.
In the 1960s and 1970s, scientists had already established a strong seasonality factor in KD cases in the United States, where most cases seem to occur in the winter and spring months. With any disease, scientists looked to uncover the
causative agent of this condition and soon realised this was proving very difficult. With no definitive microorganism to blame for the cause of KD, some scientists started looking into the possibility of an agent carried in the air by
seasonal winds.
A change in wind direction
Another study in 2011 showed that a pattern was starting to emerge globally. While Japan continued to have the highest incidence of KD, the US also uncovered an increase in incidence along the country's west coast, especially in California
and Hawaii.
Dr. Xavier Rodó, Dr. Joan Ballester and colleagues proposed to carry out an analysis of three geographically distant places that share the same seasonal cycle and variability in several cases: Japan, Hawaii and San Diego.
Although far from Japan, these US states could be subject to westerly winds originating in East Asia. The study revealed a common increase in cases associated with an Asian-North Pacific wind pattern during winter. Could the agent
responsible for KD be blowing in the wind?
To assess this association, the group utilised an atmospheric dataset combined with hospital admissions of KD, which included the biggest epidemics in Japan from 1979 to 1986. The data also included an analysis of atmospheric pressure and
winds.
Kawasaki disease cases are more common in the winter months. | Lan Pham / Unsplash
Usual wind patterns before March and May blow across Japan from the south, but closer to September—when the epidemics peak—the wind direction shifts from south to northwest. A later shift to southerly winds coincided with the end of the
epidemic.
A closer look at the years where major KD epidemics occurred, versus non-epidemic years, showed more clearly how epidemic years were associated with stronger northwesterly winds. This was observed alongside the development of an unusual low
pressure centre to the north of Japan and high pressures on the border between Russia and China, creating a pressure difference that drives the observed northwesterly winds.
These year-to-year changes in wind pattern are associated with KD cases fluctuations. Similar fluctuations were observed in San Diego, California, through the complex wind trajectories connecting the two areas across the Pacific Ocean.
Researchers also found that KD epidemics in Japan, Hawaii and San Diego were synchronised. A pathway across the Pacific characterised as a wind ‘duct’ connects distant regions from Japan to Hawaii and San Diego. This creates a plausible
scenario for a causal agent of KD to be transported by strong tropospheric wind currents across the Pacific Ocean.
El Niño and Kawasaki Disease
Another research paper showed that in years of a high number of KD cases, there was an association with enhanced northwesterly winds driven by a phenomenon developing in the North Pacific, known as El Niño-Southern Oscillation (ENSO).
ENSO is important because it can change global atmospheric circulation associated with the warming of the ocean surface, and increase rain and westerly winds. ENSO can help predict higher-than-normal KD cases in Japan preferentially occur
during either El Niño due to its role in year-to-year wind variability. It also plays into the variability in tropical diseases such as malaria, dengue and cholera.
Wind is not an easy variable to study. It can vary in intensity and direction within a short period, as well as location, but it is still an influential factor that must be studied to understand the onset of Kawasaki Disease.
The connection and synchronisation of the epidemics in Japan, San Diego and Hawaii suggested the causal agent of KD may be blowing in the wind, blowing west through strong atmospheric currents. But, what could this agent be? Researchers
have said an infectious organism is a possibility, but the presence of an environmental pollutant in the air cannot be ruled out and both hypotheses should be fully investigated.
ENSO as a climate variable plays an important role in modulating and predicting Kawasaki disease epidemics. Kawasaki cases increase in Japan during El Niño Modoki. | Yu Kato / Unsplash
One of the world-leading experts in KD research is the Barcelona Institute of Global Health (ISGlobal). An initiative led by Dr. Rodó and Dr. Ballester carried out important research with the United States and Japan to discover the cause of
KD. What sets them apart is their
interdisciplinary approach, which includes ‘climate experts, engineers, infectious diseases specialists, environmental and atmospheric experts and microbiologists that together have tested the hypothesis that atmospheric winds carry an
agent that triggers the disease on a distant continent.’
Featured Image: Martin Abegglen / Internet Archive Book Image | Flickr
Ballester J., Burns J.C., Cayan D., et al. (2013) Kawasaki disease and ENSO-driven wind circulation. Geophys. Res. Lett. Volume 40, pages 2284–2289.
Bell D.M., Morens D.M., Holman R.C., Hurwitz E.S., Hunter M.K. (1983) Kawasaki Syndrome in the United States: 1976 to 1980. Am J Dis Child.Volume 137, Issue 3, pages 211–214.
Burns J.C., Cayan D., Tong G., et al. (2005) Seasonality and temporal clustering of Kawasaki syndrome. Epidemiology,Volume 16, pages 220–225.
Burns J.C., Herzog L, Fabri O, et al. (2013) Seasonality of Kawasaki Disease: A Global Perspective. PLoS One. Volume 8, pages 1–11.
