Preliminary investigation results have revealed the bacteria in seven of the typhoid fever cases recently reported in Yuen Long may be from the same source, Centre for Health Protection Consultant Dr Thomas Tsang says.

Investigations showed that children and teenagers were predominantly affected. Most cases were localised in Tin Shui Wai and Long Ping Tsuen in Yuen Long. No single food outlet was patronised by all of the patients. Investigations are ongoing with special attention to food with localised distribution in that area and food with special appeal to young people.  

Dr Tsang said special investigations were being conducted to ascertain whether food vehicles or food handlers could be the source of infection. These include epidemiological studies and the collection of over 200 samples for laboratory testing. More results are expected over the next two to three weeks.

During the past month, starting on November 25, the centre received 12 typhoid cases, involving nine patients in Yuen Long, one in Tuen Mun and one in Sham Shui Po. One other case was classified as imported.

For the case in Sham Shui Po and the imported case, laboratory tests showed that they were unlikely to be related to the cases in Yuen Long.  Results of tests for the remaining cases are pending.

Blitz operation targets illegal food hawkers

Meanwhile, control measures against typhoid fever are being implemented in Yuen Long. Food shops connected with the cases have been inspected and blitz operations mounted on over 120 retail shops and market stalls selling siu mei and lo mei as well as meat-roasting factories. Raids on illegal food hawkers were also conducted. These operations will lower the chance of typhoid fever spreading before more definitive investigation results are available.

Since the incubation period of typhoid fever can stretch to three weeks or more, Dr Tsang said it was possible that more previously infected cases would appear in the coming two to three weeks.

A total of 36 cases of typhoid fever have been reported so far this year while the annual figures for 2001 to 2004 are 67, 67, 49 and 53 respectively.