Cases of dengue fever are soaring in Singapore, with the number of new cases in the first five months of the year exceeding the total recorded throughout 2021.
More than 8,500 cases of dengue were reported from January to the middle of May.
And dengue season, which runs from June to October, is only beginning.
The country’s National Environment Agency has issued a warning of a major outbreak in the city state this year.
Dengue, a virus spread by mosquitoes, can result in outbreaks that overwhelm hospitals.
Dengue fever symptoms
Signs of infectioninclude a high fever, headache, vomiting, muscle, ache, joint pains and a skin rash.
Experts say warning signs that could signal a more severe case include abdominal pain, increased breathing rate, a swollen liver, presence of blood in stool or vomiting.
There could be several factors behind the surge in Singapore, doctors say, including a rise in the less common serotype DenV-3, meaning most people lack immunity.
A rise in mosquitoes and more people getting out and about now Covid-19 restrictions have eased may also be playing a part, they said.
"In the UAE, dengue is rare and imported by travellers from endemic areas of the world," said Dr Brijesh Bhardwaj, a specialist in internal medicine and head of department at NMC Royal Hospital, DIP, Dubai.
In 2017 authorities in Dubai urged doctors to consider dengue as a cause of acute fever due to travel to countries where the virus is endemic, including Singapore.
A circular issued by Dubai Health Authority to all healthcare facilities said importation of dengue fever cases “is possible to UAE through visitors to the country and travel to endemic areas”.
There are four serotypes of the virus.
Becoming infected by one temporarily grants someone immunity to all four, lasting around a year, and lifelong protection from the specific type.
But catching another serotype later can lead to more severe symptoms from a phenomenon called antibody dependent enhancement.
This happens when antibodies present from a first dengue infection bind to an infecting particle of a different dengue serotype, but cannot neutralise it, instead allowing it to infect a type of white blood cell more effectively.
The virus is carried by a specific type of mosquito, the Aedes species — Ae. aegypti or Ae. albopictus — mosquito.
It transmits when a mosquito picks up dengue from an infected human, incubates the virus until it reproduces enough to form a reservoir and then bites other people.
About 4 billion people live in areas where dengue is found and 400 million people become infected with dengue each year, says the US Centres of Disease Control and Prevention. About 40,000 of them die.
A study carried out in Indonesia last year found the dengue fever rate plummets when an army of mosquitoes was infected with a virus-inhibiting bacteria.
The study resulted in a 77 per cent cut in infection and an 86 per cent fall in hospital cases in Yogyakarta city, Indonesia.
The study was inspired by the idea that mosquitoes infected with the bacteria Wolbachia do not transmit viruses to people as easily, which reduces the number of cases.
The bacteria is found in 60 per cent of insect species and resides in the same areas of the mosquito body as viruses such as dengue, where it competes for space.
This makes it harder for dengue to reproduce, meaning mosquitoes are much less likely to spread viruses.