Four more Hongkongers were confirmed to have dengue fever on Thursday, bringing the number of people who have contracted the virus locally to 23 this year – the most cases reported since records began in 1994. The four new patients were in a stable condition, the health department’s Centre for Health Protection said. They either live on or had visited Cheung Chau island, which has other infected residents, or, like those whose infections were reported since August 14, had gone to the popular Lion Rock Park. The spike in cases over a 10-day period has worried medical experts, who fear that a further outbreak will stretch the already overburdened public health system. Most dengue fever cases in previous years were imported – patients were bitten elsewhere and displayed signs of the illness on returning. The last time a large number of local cases was recorded in a short period of time was in 2002 when 20 cases were reported within two months. Since 1994, dengue has been a statutory notifiable disease, which means doctors have to report each case they treat. This year, 61 imported cases, mostly from Thailand, the Philippines and Cambodia have been reported, the CHP said. “We have informed the Guangdong and Macau health authorities to alert them to the latest situation,” a spokesman added. Dengue fever-carrying mosquitoes more widespread in Hong Kong as government urges community action The two new patients living on Cheung Chau – an island about 10 kilometres southwest of Hong Kong with homes and tourist attractions such as temples and seafood restaurants – are a married couple, a 71-year-old woman and a 76-year-old man. They live on Fa Peng Road and the man’s younger brother, a 52-year-old who is also from the island, was earlier diagnosed with dengue fever on Sunday. The couple’s 59-year-old male friend, who is also a fellow island resident, was confirmed to have the virus on Tuesday. An 84-year-old woman was the first confirmed case from the island reported last Tuesday. Battle to contain Hong Kong dengue fever outbreak intensifies, as wet weather forecast The other two new cases were an 18-year-old man who lives in Tseung Kwan O but had visited Cheung Chau recently, and a 34-year-old man whose work involved cutting grass in surrounding areas outside Lion Rock Park in Wong Tai Sin. With Lion Rock Park seeming to be the infection source for many of the earlier cases, the park was closed last Friday for 30 days for fogging to eradicate mosquito breeding sites. Dengue fever is a disease transmitted to humans by Aedes albopictus , a type of mosquito commonly found in Hong Kong. People infected with the disease usually have symptoms such as a high fever and muscle pain. Health officials had said that it was more difficult to eliminate mosquito breeding problems in Cheung Chau due to its numerous shrubs. The island’s abundance of bungalow-style houses, which have more open-air spaces and could easily have stagnant water, provide spots where mosquitoes could breed. A team with members from various public bodies, including the Islands District Council and Cheung Chau Rural Committee, visited the island on Wednesday to teach residents how to prevent mosquitoes from breeding. Meanwhile, officers from the Food and Environmental Hygiene Department on Thursday went to areas near the Sai Kung residence of a 53-year-old patient and conducted mosquito control work there.