Patient zero has a lot to answer for.
The spread of dengue fever across Hong Kong continues, with four new cases announced by the Centre for Health Protection.
That brings the number of confirmed local infections of the mosquito-borne virus to 23 since the start of the month.
Two of them are residents of Cheung Chau and another had visited the island.
The fourth patient had been near Lion Rock Park in Wong Tai Sin.
Dengue fever is clinically characterised by high fever, severe headache, pain behind the eyes, muscle and joint pain, nausea, vomiting, swollen lymph nodes and rash.
Some people may not develop symptoms, while others may experience only mild fever.
The virus’ incubation period ranges from three to 14 days, though is commonly four to seven. The CHP advised travellers returning from affected areas who feel unwell to seek medical advice quickly.
More details on this fact sheet.