A total of 46 melioidosis infection cases were recorded in Hong Kong last year, among which 30 cases in Sham Shui Po were recorded between August and December. Teaming up with Dr Tommy Lam, Associate Professor from the School of Public Health of The University of Hong Kong, Dr Gilman Siu, Associate Professor from the Department of Health Technology and Informatics of PolyU, recently conducted a study which suggested that the melioidosis outbreak in the district could be caused by airborne transmission. 

The research team collected air and soil samples in the Sham Shui Po district between August and October last year. Air samples were collected from a Pak Tin Estate construction site five days after a typhoon and confirmed for the first time that the bacteria had remained in the air after the storm. Whole-genome sequencing confirmed that Burkholderia pseudomallei isolated from the air sample showed high genomic similarity to the clinical cases in the Shum Shui Po district, both belonging to the novel sequence type ST-1996. In addition, it was also noticed that from August to October, over 70 per cent of melioidosis patients in Shum Shui Po developed pneumonia. 

“These clinical and epidemiological findings all suggested that the outbreak in Sham Shui Po was caused by airborne transmission,” said Dr Siu in a press conference held at the end of last year. 

The team also pointed out that unvegetated soil in the area has been increasing since 2016. “This could facilitate the movement of bacteria, which were originally located deep in the soil, to the surface layer during periods of heavy rainfall. The aerosolised soil could then be dispersed by strong winds, thus causing airborne transmission,” added Dr Siu, as he called on members of the public to be extra cautious during the typhoon season.

Meanwhile, further study will be required to identify the level of drug resistance and toxicity of ST-1996. The research team will continue their efforts to identify the source and “hotbed” of the bacteria.