A:
Dengue fever, spread by mosquitoes in tropical areas, is caused by 4 different types of dengue virus, and protection against one unfortunately does not give protection against the others, so the illness can be contracted up to 4 times. Historically the different types were geographically isolated, but nowdays 2, 3 or even 4 types can be found in the same places, especially through SE Asia.
Identifying the type can be done in a laboratory, but generally there is no point, as future exposure can be to any other type anyway. It is recognised that having a second or third infection after a previous one slightly increases the risk of a more serious illness on the second or third occasion. The chance of having a more severe illness is estimated to be about 2 %. That does not mean you cannot travel there, but does mean you should be more careful to avoid mosquito bites.
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