HONG KONG, July 7 (AP) -- The rat population seems to be shrinking in Hong Kong's urban areas, but cases of rodent-related diseases are increasing outside the city, the government said Friday.

The number of people infected with scrub typhus -- a potentially fatal disease caused by mites that live on rodents -- grew to 30 last year from 13 in 2003 in rural areas, the government said.

There have been five confirmed and five suspected cases in 2006.

"We believe the number of scrub typhus cases may continue to increase this year. Citizens should take precautionary measures when they go hiking," said Dr. Ho Yuk-yin, a consultant with the Food and Environmental Hygiene Department.

Scrub typhus symptoms include fever and headache.

In urban areas, the number of rats seems to be declining, the government said.

Officials gauge the rat population by setting out food and noting how much has been taken away. Only 4.4 percent was taken away in 2005, far less than the 16 percent in 2000, a government study said.

"We are satisfied with our effort to eliminate rodents in urban areas, but the hazard lies in rural areas," Ho said.

The government did not give any figures for the rodent population in rural areas.