That Wretched Aedes

Mosquitoes have been around for millions and millions of years; dinosaur DNA was extracted from a fossilized mosquito in the movie ‘Jurassic Park’. Today I am not crediting the mosquito at all, in fact I am writing about a serious disease that mosquitoes transmit.

Aedes aegypti mosquitoes carry the Dengue virus – a type of flavivirus. Other diseases involving flaviviruses would be Japanese Encephalitis (SEA) and Murray Valley encephalitis (Aus).

All 4 types of dengue have similar clinical presentations – sudden onset fever, headaches, backpain with severe myalgia. Macular rash and red eye are also signs of dengue fever. Other symptoms include anorexia, nausea and paraesthesia. Due to the severe thrombocytopenia (low platelet count) associated with dengue, epistaxis (nose bleeding), gum bleeding, petechiae and bleeding from existing GIT lesions are common. The disease usually lasts between a week and 14 days in an uncomplicated case.

As with other viruses, you can’t get dengue from the same serotype a second time. (You can’t get dengue 1, twice) However, a second infection from a different serotype of dengue can cause Dengue Haemorrhagic Fever – fortunately, this is rather rare.

Diagnostic investigations include FBE, IgM ELISA (serology) and RT-PCR during the acute phase.

A report from Singapore tells the tale of the situation there

The dengue situation here has hit epidemic level for the first time since 2005, with 401 cases reported last week.

The outbreak is officially regarded as an epidemic when more than 378 cases are reported in a week. The last dengue epidemic was in October 2005, when the weekly tally hit 387.

Last week’s figure is a hefty 37 per cent increase from the 293 reported cases the week before.

The 2,868 cases in the first six months of this year is double the number for the same period last year.

As you can see, the scale of the problem is NOT small. Researchers are already confident that a vaccine will be found; but even after that, clinical trials will take ~7 years before the vaccine can be approved and released.

From the same article as above:

Scientists are racing to find a vaccine for dengue and to discover the reasons why dengue epidemics are becoming more frequent.

And while a drug could be ready for human testing by the end of next year, the research still has a long way to go. Professor Paul Herrling, chairman of the Singapore-based Novartis Institute of Tropical Diseases, said it would take up to seven years to get the drug onto the market if initial trials are successful. In the meantime, there is a risk the virus will mutate, he said.

Lucky for me, I’m not residing in a dengue-endemic area at the moment. If you ARE living in the tropics, please protect yourself from dengue: use some insect repellent and avoid densely forested areas.

Also refer to the dengue prevention checklist provided by the National Environmental Agency of Singapore to see how you can keep your environment mosquito-free.

Reference: Kasper et al (ed.) (2005) Harrison’s Principles of Internal Medicine, 16th Ed., McGraw-Hill