Also known in English as breakbone fever, dengue has returned to Brazil lately. The disease has become so widespread it threatens to become a public health problem. In the Americas, dengue is an acute infectious disease transmitted by the Aedes aegypti mosquito, the yellow fever mosquito. In Asia it is transmitted by another mosquito.
Dengue is complicated in that it consists of various types - type 1, 2, 3 and 4. The symptoms in all four types are the same: headache, muscular and joint pains, fever, diarrhea and vomiting.
Besides four types, the disease comes in three forms: classic, mild and hemorrhagic, which may result in dengue shock syndrome. A person who gets type 1 will be immune to type 1 in the future; this is also true of the other types.
However, the catch is that each time a person who has already had dengue is infected by a new type, there is a tendency for the disease to be worse. And as a person is infected by different types over a period of time, the possibility of getting the worst kind of dengue, hemorrhagic, increases.
Although most types and forms of dengue may be painfully uncomfortable, recovery is normal within two weeks. Hemorrhagic dengue, on the other hand, can be fatal.
At the moment, a new type of dengue has returned to Brazil - type 4. Health officials are concerned as type 4 dengue has not been seen in Brazil for almost three decades.
Celso Granato of the Federal University of São Paulo (Unifesp) explains that type 4 is not more dangerous, infectious or fatal than other types, but as it has not circulated for so long, people are not immune to it.
As a result, people who have had other types that have been in circulation recently face the possibility of more serious consequences if they get type 4.
"Some people can get dengue for a second or even a third time, after having type 1 or 3 (which are more common in Brazil). Unfortunately, they will be more susceptible to type 4," says Granato.
An infectious disease expert, Edmilson Migowski, at the Rio de Janeiro Federal University (UFRJ), says that because the type 4 has been absent from Brazil for so long it could easily become an epidemic.
"If nothing is done to increase mosquito control, we could have a drastic situation in the summer of 2012. A dengue type 4 epidemic will not spare anyone," declared Migowski.
Data from the Ministry of Health shows that around 80% of all dengue cases in Brazil are type 1. So far, according to a ministry survey, dengue type 4 has been found in a little over 5% of cases in three states: Roraima, Amazonas and Pará (all three states are in the northern part of the country, in the Amazon region).
Cases have also been reported in Rio de Janeiro, Bahia and Piauí.
Brazil's Ministry of Health has recognized that dengue type 4 poses a threat and has requested that state authorities increase mosquito control and expand urban clean up operations. The ministry has also made notification of dengue type 4 cases mandatory.