Hong Kong's Centre for Health Protection (CHP) of the Department of Health has confirmed two new cases of leptospirosis involving participants of the hiking activity "Team Challenge 36" held in August.
A CHP spokesman said: "The two affected are a 36-year-old man and a 19-year-old woman. Their blood samples were confirmed positive for leptospirosis today."
CHP's investigations revealed that the two cases were epidemiologically linked to the leptospirosis case involving a 21-year-old man confirmed last week.
The 36-year-old man was reported to develop fever, chill and vomiting on September 5 and admitted to Ruttonjee Hospital on September 8. He had recovered and was discharged on September 16.
He had his left leg and elbow wounded and soaked with water during the activity.
In the woman's case, the patient developed fever, headache and muscle pain on September 7 and sought medical treatment from a government clinic on September 9. Her symptoms gradually improved without hospitalization and had recovered.
She had also visited some stream areas and participated in rafting during the activity. She had multiple abrasions, not properly covered, over both upper limbs and feet during the hiking.
Both patients' family members and team members do not have symptoms of the disease at present.
Meanwhile, CHP also tried to contact some other 400 participants of the activity to screen for symptoms, provide health advice and make referrals as necessary. At present, none of the 309 persons followed up so far have symptoms of the disease.
The spokesman said leptospirosis is a zoonotic disease caused by the bacteria leptospira. Leptospira organisms can be found in some animals including rodents, cattle, pigs, horses, and dogs.
Most human infections occur through contact with urine excreted by infected mammals primarily through skin abrasions, open wounds or mucous membranes, and occasionally through ingestion or inhalation. Leptospirosis is normally not transmitted from person to person and the incubation period is usually between 4 and 19 days.
"Patients with leptospirosis commonly present with a flu-like illness with high fever, headache, muscle pains, red eye, sore throat and rash. In some cases, the disease can cause anemia and affect the liver, kidneys, lungs, and other internal organs. The disease can be treated effectively with antibiotics," the spokesman said.
"The risk of leptospirosis infection can be minimized by covering open wounds properly and avoiding contact with urine of live mammals and objects contaminated by them as well as polluted water."
"Overseas outbreaks of leptospirosis are usually related to occupational or recreational water exposures, such as water contaminated with urine of infected animals," the spokesman said.
The incidence of leptospirosis is low in Hong Kong. There were one local case in 2001, 2 local cases in 2002, 1 imported case in 2003. So far this year, there are 1 imported and 4 local cases.