Sharp Drop in Kawasaki Disease Cases Amid COVID-19 Sparks Investigation

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Sharp Drop in Kawasaki Disease Cases Amid COVID-19 Sparks Investigation

Sharp Drop in Kawasaki Disease Cases Amid COVID-19 Sparks Investigation

Mysterious Kawasaki Disease Sees Drastic Decline by Two-Thirds After COVID Outbreak – Clues for Unraveling?

The number of patients with the mysterious Kawasaki disease, which primarily affects infants and causes inflammation in the body’s blood vessels, has drastically decreased by two-thirds since the onset of the COVID-19 pandemic, according to a study by the Japan Kawasaki Disease Research Center, a non-profit organization.

Kawasaki disease, first reported by the late Dr. Tomisaku Kawasaki in 1967, still lacks a known cause. To shed light on the cause, experts are conducting investigations based on the changes in the number of cases.

Sharp Drop in Kawasaki Disease Cases Amid COVID-19 Sparks Investigation

Kawasaki disease mainly affects children under the age of five, causing inflammation in the body’s blood vessels. Symptoms include high fever, congestion in both eyes, a tongue turning as red as a strawberry, and a rash with a reddish tint appearing all over the body.

In severe cases, patients can develop lumps in the “coronary arteries,” which supply blood to the heart, posing the risk of heart muscle damage. About 3% of patients develop some form of lump, leading to potential long-term effects.

In Japan, before the COVID-19 outbreak in 2019, the number of patients was on the rise, reaching approximately 17,000 cases in that year. The incidence rate (per 100,000 population aged 0-4) in 2019 was the highest on record at 370.8 individuals. The domestic incidence rate was the highest in the world.

However, after 2020, the number of patients sharply decreased. According to a nationwide survey by the same center, the number of patients in 2020 was 11,173, and in 2021 and 2022, it remained below 12,000. The incidence rate was 250.6 in 2020, dropping below 300 for the first time in eight years. It remained in the 200s in 2021 and 2022.

While the mechanism of onset is still not understood, researchers have a hypothesis. It suggests that individuals with certain predispositions to Kawasaki disease may develop the condition when exposed to viruses or microorganisms such as bacteria, triggering an excessive immune response. This hypothesis, based on patient surveys, indicates that there may not be just one triggering microorganism.

According to Dr. Koichi Nakamura, Director of the center and Honorary Professor of Public Health at Jichi Medical University, until 2019 in Japan, the highest number of patient reports was in January, followed by August. On the other hand, countries like South Korea and Taiwan see more cases in early summer. Nakamura explains, “If the number of patients varies with the season, it could be explained by the involvement of multiple microorganisms influenced by the climate.”

With the rise of COVID-19, measures such as mask-wearing, handwashing, and maintaining social distance for infection prevention have been strictly implemented. Due to these measures, the prevalence of seasonal influenza was minimal in 2021-2022, and many viral infections, particularly those affecting children, decreased.

Why did Kawasaki disease follow suit? Nakamura suggests two possibilities. One is that the thorough practice of handwashing and disinfection may have washed away the microorganisms triggering Kawasaki disease. The other is the decrease in outdoor activities. In the case of infectious diseases in infants and young children, parents may introduce bacteria or viruses, but with reduced outings by family members, the introduction of microorganisms triggering Kawasaki disease may have decreased.

While fears of COVID-19 led to reduced visits to medical facilities in some cases, Kawasaki disease has distinctive symptoms, such as prolonged fever and redness and swelling of the hands and feet. It is believed that many people did not refrain from seeking medical attention.

In South Korea, the country with the second-highest number of patients after Japan, there has also been a decrease in Kawasaki disease cases since the COVID-19 outbreak. According to a research group including Yonsei University College of Medicine, the number of Kawasaki disease patients from February to September 2020 decreased by about 60% compared to the period before the COVID-19 outbreak.

Nakamura states, “By comparing the changes in the number of patients over the three years from 2020 and the local situation of COVID-19 outbreaks, we want to clarify which of the two possibilities had an impact. By doing so, we can come a little closer to understanding the cause of Kawasaki disease. We also want to closely monitor the trends in the number of patients this year, where social activities have changed significantly.”

What is Kawasaki Disease?

Kawasaki disease is a rare but serious condition that primarily affects children under the age of five.

It involves inflammation of the blood vessels throughout the body and can lead to various symptoms, including high fever, redness and swelling of the hands and feet, and a characteristic strawberry-like appearance of the tongue.

In severe cases, it can result in complications affecting the heart, such as the development of lumps in the coronary arteries.

The cause of Kawasaki disease remains unknown, and its onset is not fully understood. It gained attention recently due to a significant decrease in cases during the COVID-19 pandemic, prompting investigations into potential connections.