About half of the world's population is at risk of contracting dengue, according to the World Health Organization. The mosquito is found in tropical and subtropical climates around the world; however, dengue does not naturally occur in these creatures: the mosquitoes get dengue from us.
The mechanism of dengue infection is simple. Female mosquitoes bite humans because they need the protein found in our blood to produce eggs. (Male mosquitoes do not bite.) Ifthe mosquito bites someone with dengue - and then, after the virus's roughly eight- to 12-day replication period, bites someone else - it passes dengue into its next victim's bloodstream.
There is no vaccine against dengue, but infecting mosquitoes with a natural bacterium called Wolbachia blocks the insects' ability to pass the disease to humans. The microbe spreads among both male and female mosquitoes: infected females lay eggs that harbor the bacterium, and when Wolbachia-free females mate with infected males, their eggs simply do not hatch. Researchers are now releasing Wolbachia infected females into the wild in Australia, Vietnam, Indonesia and Brazil.
Scientific American, June 2015, Adaptado.
De acordo com o texto, a infecção por dengue
- A propaga-se quando mosquitos fêmeas picam seres humanos infectados e retransmitem a doença a outras pessoas.
- B é provocada por mosquitos infectados depois do acasalamento.
- C desenvolve-se por meio das fêmeas, que transmitem o vírus para os machos, num círculo vicioso que se repete periodicamente.
- D desenvolve-se no corpo humano após doze dias da picada, período de incubação do vírus.
- E altera a proteína presente no sangue humano que é procurada pelos mosquitos fêmeas.