NewScientist.com news service
Debora MacKenzie
From Site:
With 50 million cases in the tropics each year, dengue fever is humanity's most common insect-borne viral infection. Killing the mosquitoes that carry it is the only way to fight it, but now a large-scale survey in Thailand has revealed that this can make the deadliest form of dengue more prevalent.
Known as "breakbone fever", dengue is painful but normally not fatal the first time around – the real threat is the second infection.
There are four varieties, or serotypes. Say you get bitten by a mosquito carrying serotype A, and then a year later by one carrying serotype B. The antibodies you made in response to A bind to the B virus but do not destroy it.
Instead these pairs overstimulate the immune system, causing a potentially fatal disease called dengue haemorrhagic fever. DHF kills 12,000 people a year, mainly children.
Temporary immunity
However, for a few weeks after you contract dengue, you have a kind of immunity that does destroy other serotypes.
If you get serotype B during these weeks, you will not develop DHF but will develop antibodies to both A and B. If you get infected by all the serotypes during such a window of cross-immunity, you can end up with antibodies to all of them and won't develop DHF.
[via: http://www.newscientist.com]
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