An infectious disease specialist has called on Hong Kong authorities to step up rodent checks, despite confirmation that no residents from the city were on board the hantavirus-hit cruise ship in the Atlantic Ocean.

Speaking on an RTHK programme on Friday, physician and infectious disease specialist Dr Joseph Tsang said the Agriculture, Fisheries and Conservation Department (AFCD) should conduct regular monitoring of rats.

“The AFCD should conduct regular monitoring to test whether rats in the environment carry viruses,” he said.

The Centre for Health Protection (CHP) previously issued a statement on Thursday, saying there were no Hong Kong residents on the hantavirus-stricken cruise ship, which carried 147 passengers and crew members.

The CHP also said that, as of Wednesday, no infections had been reported in Hong Kong.

According to the World Health Organization (WHO), as of Thursday, there were eight reported cases linked to the MV Hondius, including three deaths. Five of the eight cases have been confirmed as hantavirus.

‘Cannot let our guard down’

Hantavirus is primarily transmitted through direct contact with the faeces, saliva or urine of infected rodents, or by inhaling aerosolised particles of their waste, according to the CHP. Human-to-human transmission is relatively rare, and there is currently no vaccine to prevent infection.

The risk to global health posed by the cruise ship incident is low, the CHP added, citing the WHO.

Tsang said that, despite the low risk, he still urged cleaners to be aware of the dangers.

“I wouldn’t say the risk of infection in Hong Kong is especially high, but we cannot let our guard down,” the physician said.

“Hantavirus is usually concentrated in places with more rats, such as refuse collection points, rear stairwells, or the back alleys of restaurants. Sanitation workers should take particular care.”

Dengue fever poses a “moderate” risk to Hong Kong, a health official has said after the city recorded its first local case of the infection this year.

Albert Au, head of the Centre for Health Protection (CHP), said in an RTHK radio programme on Wednesday that rising temperatures and the imminent rainy season made environments more favourable for mosquito breeding.

“The infection rate for mosquito-borne diseases in Southeast Asia and neighbouring regions remains high,” Au said in Cantonese. “So we think the risk of an outbreak cannot be neglected.”

Hong Kong is investigating a local case of dengue fever after a 21-year-old man, who had not travelled outside the city lately, tested positive for the dengue virus.

According to a government statement on Tuesday, the man developed symptoms including fever and a rash last week, and is currently in stable condition in hospital.

He told authorities he had recently been bitten by mosquitoes near a construction site in Penny’s Bay on Lantau, where he works.

Environmental inspections showed there were “multiple sites conducive to mosquito breeding” there, including drainage channels with weeds and leaves, as well as stagnant water, the statement read.

The man lives at Tai Wo Estate in Tai Po. The CHP has set up a consultation booth at the estate to provide health assessments and dengue fever antibody tests for people with symptoms.

12 imported cases this year

So far, 12 other cases of dengue fever have been recorded this year, all of them imported.

Dengue fever, a viral infection transmitted to humans through mosquito bites, is most commonly recorded in warmer climates, according to the World Health Organization (WHO).

Most people experience mild or no symptoms, although severe cases – often caused by multiple infections – can lead to death.

Au said there might have been undiagnosed imported cases of dengue fever in the community that transmitted the virus locally. However, authorities have not found epidemiological links between the man’s case and other previously recorded imported cases.

In 2025, the city recorded 59 cases of dengue fever, all imported. In 2024, there were 161 cases, five of which were local.

According to the government statement, the 21-year-old’s household contacts and workers at the construction site are so far asymptomatic.

Members of the public are advised to inspect their homes and prevent water accumulation to remove potential mosquito breeding grounds.