Hongkongers have been urged to wear masks in crowded places when visiting Japan following the death of a Hong Kong resident in Osaka due to necrotizing fasciitis caused by a group A streptococcus infection, or "flesh-eating disease."

Japan has witnessed a surge in cases of the disease since the fourth quarter of last year.

In the first 11 weeks of this year alone, as many as 335 cases of streptococcal toxic shock syndrome were reported, significantly higher than the average annual count of 48 incidents over the past six years, according to University of Hong Kong microbiologist Ho Pak-leung.

"I believe the increase in cases is linked to the relaxation of social distancing measures implemented for Covid-19," Ho said in a radio program yesterday.

"While the number of cases has started to decline in March, it remains at a high level compared to previous years, indicating that the peak of group A streptococcus infection has yet to pass."

Outbreaks of this nature typically occur every five to 10 years and Hong Kong experienced a significant number of cases between 2011 and 2017.

While the risk of contracting group A streptococcus is thought to be not high, Ho advised individuals to take precautions when traveling abroad, particularly by ensuring proper wound care to prevent serious complications.

"The most important thing to prevent the disease is that people who are injured during their trips should take care of their wounds. As people are relaxed during trips, they may forget to clean their wounds or fail to see a doctor in time," Ho said.

"People should also wear masks in crowded areas. But it is not necessary to wear masks all the time during the trip," he added.

He also reminded citizens to practice good hygiene as the lifting of Covid-19 restrictions is expected to lead to an increase in infectious diseases.

The Department of Health in Hong Kong said patients who suffered from necrotizing fasciitis in Japan will be investigated for their exposure history in both Hong Kong and Japan. The department added that group A streptococcus can be transmitted through droplets or direct contact with infected respiratory secretions.

The infection can result in scarlet fever, pneumonia, meningitis, or even serious streptococcal toxic shock syndrome. Although no vaccine is available for the infection, effective treatment with antibiotics is possible.

The Immigration Department said it has received a request for assistance from the patient's family and is coordinating with the Commissioner's Office of China's Ministry of Foreign Affairs in Hong Kong and the Consulate-General of The People's Republic of China in Osaka to address the incident.

Japan visitors urged to mask up after death of HK tourist