A Sham Shui Po district councillor on Wednesday urged health authorities to do more to track down the source of a spate of cases of potentially deadly bacterial infection.

Some 29 cases of melioidosis have been detected in the SAR so far this year, with 20 in the Sham Shui Po district, but health experts have not yet identified the source, sparking concern among residents. Six of the patients have since died, all of whom had underlying diseases or immunodeficiency.

Melioidosis is transmitted through muddy water and soil, though human-to-human and person-to-person transmission is rare. The Centre for Health Protection says the mortality rate can be between 40 and 75 percent, although it is treatable with antibiotics.

Officials have carried out random sampling work in the five buildings where the patients live, but councillor Shum Tak-shing says the work should be extended to other buildings, as well as the places where the patients work and places they typically visit.

He also called on the authorities to be more transparent and publish details of patients’ whereabouts and habits.

The Centre for Health Protection said on Tuesday that all 107 environmental samples it collected in Sham Shui Po had tested negative, while top microbiologist Yuen Kwok-yung’s team found two out of 31 environmental samples collected in patients’ home tested positive.

A spokesman for the CHP said that melioidosis bacteria can survive in the local environment and that melioidosis cases have been recorded in Hong Kong each year. Infection cases are said to be more common after typhoons or storms.