The authorities in Japan appear concerned about the spread of a potentially deadly infection.
This assessment was issued to clients of Dragonfly’s Security Intelligence & Analysis Service (SIAS) on 21 June 2024.
- The National Institute of Infectious Diseases on 18 June reported a record number of cases of streptococcal toxic shock syndrome so far this year
- Even so, we assess that other countries in Asia are unlikely to restrict travel to or from Japan
A severe infection is spreading in Japan. The medical authorities there have issued several warnings in recent months over streptococcal toxic shock syndrome (STSS), an infectious disease that is often fatal. The outbreak of STSS has been growing since 2023, primarily in southern and central regions of Japan, including Tokyo. But the number of cases per 100,000 people countrywide is still low, according to the Hong Kong medical authorities. So on current indications, we assess that any restrictions on movement within Japan or international travel to or from the country are unlikely.
We are only moderately confident in this assessment. This is because the medical authorities consider the strain of bacteria that seems to be driving the outbreak as very transmissible and pathogenic. And it is transmitted by droplets or close contact, according to the National Institute of Infectious Diseases (NIID). So we would anticipate targeted control measures in cities if the number of new cases significantly rises in the coming weeks. Any findings that the disease is more infectious than previously thought would make restrictions on international travel reasonably likely.
Record number of cases reported this year
The number of STSS cases seems to have accelerated this year. On 18 June, the NIID said it had reported 1,019 cases across Japan as of 9 June, which is already higher than the number of cases during the whole of 2023 (941). Its data reportedly shows that most cases this year have been reported in Tokyo (150), followed by Aichi prefecture in central Japan (69) and Saitama prefecture near Tokyo (68). According to the NIID, both the number of STSS cases and the proportion of deaths has increased, especially among those under 50 years of age.
The STSS can be caused by a number of bacterias. However, the Japanese authorities warned in December 2023, and again in March that a form of STSS caused by a specific bacteria, Group A Streptococcus (GAS), had been spreading since July 2023. It seems to have issued the warnings because STSS caused by GAS is often more severe and deadly than STSS caused by other types of bacteria and requires rapid medical intervention. The authorities also pointed to a ‘highly pathogenic and transmissible’ lineage of GAS as one of the reasons behind the spread of the infection this year.
The government seems unlikely to implement widespread control measures
We have seen few signs that the authorities in Japan are considering implementing control measures, such as movement restrictions, to contain the spread of the infection. In early March, the Tokyo Metropolitan Government issued a warning over a rise in STSS cases there. But it has mainly urged people to seek medical attention if they notice symptoms, such as fever or swelling in the limbs. And the NIID has in its recent advisories also stopped short of suggesting any potential social restrictions should the situation deteriorate.
The recent warnings do seem to indicate concern among the authorities over the potential impact of the infection. The rate of the infection this year is still low, both in Tokyo (1 case per 100,000 people) and nationwide (0.8). These rates are considerably lower than that of Covid-19 during 2020-2022. But STSS has a comparatively high mortality rate, with around 30% of cases resulting in deaths according to the NIIS. We would anticipate the authorities to impose localised control measures should the rate of cases significantly rise. Or if information emerges that the disease is more infectious than officials previously thought, or that it is becoming more transmissible. Even then, such measures would probably include mask mandates, social-distancing measures or restrictions on nightlife such as limits on capacity and the sale of alcohol, based on the authorities’ response to Covid-19 pandemic.
According to the NIIS, the bacteria behind the STSS is transmitted by droplets (such as by infected people sneezing or coughing) or by person-to-person contact. But the institute said in March that ‘collection of strains and epidemiological information is required’ to understand the current situation. It has not issued an update on its understanding since. It also said in March it is ‘unclear’ why the lineage of GAS circulating in Japan has led to an increase in deaths among those under 50 years of age.
Outlook for travel restriction
Governments in Asia also do not seem to be planning to restrict travel to or from Japan due to the infection. The Hong Kong authorities on 14 June urged the public to keep ‘a high standard of personal hygiene’ while in Japan. But they added that there is no need for concern for now as the number of cases compared with the size of the population is still low. We have seen no announcements over the issue by other countries in the region. But they will also probably update their travel advisories in the coming weeks urging caution around hygiene when travelling to the country.
Image: Japan Battles Against The Coronavirus Outbreak. Photo via Getty Images.
