In Rio, rife with dengue, bacteria-infected mosquitoes are making a difference

NITEROI (AP) — Since Rio de Janeiro declared a public health emergency after an outbreak of dengue fever last month, the city has ramped up testing capacities, opened up a dozen dengue health centres and trained medical staff to attend to the ever-growing needs of its population.

But in Rio's sister city of Niteroi, just across the Guanabara Bay, it's a different story. Home to about half a million people, Niteroi has had just 403 suspected cases of dengue so far this year, and its incidence rate per capita is one of the lowest in the state, with 69 confirmed cases per 100,000 people.

By comparison, the city of Rio has an incidence rate of 700 per 100,000 people, with more than 42,000 cases.

The dengue virus is passed between humans by infected mosquitoes, but a type of bacteria called Wolbachia can interrupt transmission of the disease.

Health officials say a pilot program launched in Niteroi in 2015, in which scientists breed mosquitoes to carry the Wolbachia bacteria, has helped the city in its battle against dengue.

The Wolbachia strategy was pioneered over the last decade by the nonprofit World Mosquito Program. It was first tested in Australia in 2011 and the group has since run trials in more than a dozen countries, including Brazil. The initiative provides an appealing alternative at a time when the UN health agency warns that reported cases of dengue globally increased tenfold over the last generation.

In Niteroi, Mayor Axel Grael said he sought help after the 2012 dengue epidemics, when officials received thousands of notifications and one person died. The city sealed a partnership with the state-run Fiocruz Institute, the World Mosquito Program and the Health Ministry, and cases have been going down ever since.

“It was a moment of great concern in the country and in Rio,” Grael recalled in an interview Friday with The Associated Press in Niteroi. “Today, after applying the Wolbachia technique, we have a much better results.”

Dengue is a viral infection transmitted to humans through infected mosquitoes. Many who are infected never develop symptoms, but others get a high fever, headaches, body aches, nausea and a rash. While most get better after a week or so, some develop a severe form that requires hospitalisation and can be fatal.

Frequent rains and high temperatures, which accelerate the hatching of mosquito eggs and the development of larvae, make the famously hot city of Rio especially susceptible. Every couple of years, outbreaks become epidemics.

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