A mosquito-born illness will affect almost everyone in Indonesia

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Officials in Indonesia might be underestimating the true extent of a severe, mosquito-born illness, according to a new study, because many cases go unreported, per the World Health Organization.

Dengue fever, also called breakbone fever, is a virus closely related to and carried by the same mosquitoes as Zika. Many cases are mild, but in some people dengue can cause extreme pain, fever, shock, and hemorrhaging, and the risk of severe consequences increases the more times someone is infected.

Why it matters: In some countries dengue is a leading cause of death in children, according to WHO.

What they did: The researchers recruited 3,210 children aged 1-20 from neighborhoods across Indonesia. They then tested the participants' blood for dengue antibodies. Since antibodies stay in the body for years after an infection, they provide a glimpse into a person's disease history.

What they found: 69% of Indonesian children had dengue antibodies, and that number rose to 80% in children over 10. The numbers are high enough that the authors suggest that some cases of symptomatic dengue might be going unreported.

This doesn't mean that 80% of Indonesian children get sick from dengue. Many of them may not have even known they were infected. However, these people could still be at risk of more severe symptoms, were they to be infected again. Additionally, people without symptoms can still transmit dengue to mosquitoes, and from there to other people.

Go deeper: Dengue is one of the fastest spreading diseases in the world, and the Centers for Disease Control and Prevention in the U.S. estimates that over 30% of the global population is at risk of dengue. Modern occurrences in the U.S. are fairly rare and with a few exceptions only involve a handful of cases, but mosquitoes capable of spreading dengue have established themselves in many parts of the country where they are closely monitored for the disease.