While governments around the world are adopting various mosquito-controlling measures to fight dengue, a large-scale survey in Thailand has revealed that fewer mosquitoes may increase the prevalence of the deadliest form of the disease.

Yoshiro Nagao and colleagues at the London School of Hygiene and Tropical Medicine say that dengue, which is also known as "breakbone fever", is generally not fatal for the first time around.

The researchers say that the real threat is the second infection.

According to them, there are four varieties of infection, which are scientifically known as serotypes.

The researchers say if a person is bitten by a mosquito carrying serotype A and then a year later by one carrying serotype B, the antibodies made in response to virus A would bind to the virus B but not destroy it.

They say that such pairs instead over-stimulate the immune system, causing a potentially fatal disease called dengue hemorrhagic fever (DHF).

Nagao says that for a few weeks after a person contracts dengue, one has a kind of immunity that destroys other serotypes.

Just in case a person gets serotype B during such weeks, he/she will not develop DHF, but will develop antibodies to both A and B.

The researcher says that if a person gets infected by all the serotypes during the period of cross-immunity, he/she will develop antibodies to all of them.