Vanesca Barbosa holds up a map of the Palestina neighborhood of Aracaju, the state capital of Sergipe, in northeastern Brazil. The health department official says she and her team will visit each site marked with a red dot. These mark spots where the Egyptian tiger mosquito may breed: "Buckets, tubs, sinks, water tanks, anywhere water can collect. Eighty percent of the problems come from people's homes," says Barbosa.
The Egyptian tiger mosquito (Aedes aegypti), also known as the yellow fever mosquito, is a disease vector for viruses such as chikungunya, Zika, and dengue. All three viruses are spreading across Brazil, but foremost among them is dengue. Since the start of the year, some 1.4 million cases have been registered across the country, six times as many as the same time period last year.
A few days ago, a team from the city's environmental agency flew drones over this impoverished neighborhood on the fringe of the city. They pieced together 989 photos to create the map that Barbosa is using. Now, a team of 120 people — 50 from the city health authority and 70 city street cleaners — are going house-to-house to inspect the individual sites.
Workers pull old sofas, tires and plastic refuse from Elaine Lorenco's yard. The 32-year-old says her neighbors threw it over her fence. "We keep asking them to stop throwing garbage into our yard, but they do anyhow — in the middle of the night or before dawn." Water collected in such refuse is a perfect breeding ground for the tiger mosquito.
'Most don't believe that dengue is real'
Elaine is concerned about the health of her family. Her nephew recently spent 15 days in the hospital with dengue, as did her mother. She also has a 9-month-old baby and a 6-year-old daughter, both of whom could be infected. The same goes for her 4-year-old son Anthony, who helps with the cleanup.
Two streets away, Ronisy Santos of the health department enters a back courtyard. At first, the owner's dogs didn't want to let her near the sink she wants to inspect. What is she looking for? "Water containers, to see if they contain mosquito larvae." She says mosquitos also breed in the large blue water tanks that people here have on their roofs: "They are often left open, and that is where the mosquitos breed," says Santos. "We always warn people, we tell them again and again, but unfortunately they just don't get it."
The men and women from the health department know where the biggest problems are: "It is often the elderly. They don't believe dengue is real. It doesn't matter how often we explain it to them, they just refuse to believe us," says Edina Andrade Pereira, another health department worker. "It is just like the vaccines they refuse to get because they are convinced they are somehow harmful," adds Vanesca Barbosa.
That backwardness and lack of knowledge has a human cost. "It's a cultural thing," says Barbosa. She says she finds mountains of garbage at some homes: "And people think that's normal. But it's not; it's a risk for the whole neighborhood." Barbosa says the worst "garbage collectors" should receive psychological help so that they can change their unhealthy habits.
Read more: The most dangerous mosquito-borne diseases
Fever descending on the city
This year, dengue is also spreading rapidly on Sergipe's damp coast, says Sidney Sa, who leads the state's fight against epidemics. She says the fever began in the state's most arid regions: "The lack of water that is plaguing many communities has led them to collect and store water, and many people do so in an unsafe way." Sa says she and her team must often pour insecticide into such containers to kill larvae.
Sa and her team have also been traveling through the state for years to inform people of the dangers of dengue. Still, she says the virus keeps spreading. Sa says some residents tell her they filter or boil the water to kill any larvae before drinking it. She says they just don't understand that the virus is transmitted through mosquito bites, not by drinking unclean water. "We depend on residents' understanding of the problem, and we always ask for their aid," says Sa. But, she adds, that doesn't usually help.
The problem is being further aggravated by the improvised expansion of cities, environmental destruction and the unusually wet periods that have accompanied climate change — all of which profit the mosquitos. Sa says she and her department are short-staffed, and the state simply doesn't have the budget to finance measures necessary to win the battle. She says sometimes there isn't even enough money to pay for insecticide.
Authorities in Sergipe — which has 2.3 million residents — say current statistics show 4,000 registered cases of dengue infection in the state. That is far more than last year, but other states are getting hit even worse. And Sergipe has seen harder times, too. "During the last major epidemic, in 2008, we had 70,000 cases and 56 deaths," says Sa.
Still, she says the risk this time is greater: "This epidemic is different. We have had far fewer cases, but 12 confirmed deaths."
Most infections are Type 2 dengue virus, a form that is much more aggressive, and in which the time between the onset of symptoms and death is very short. For health workers, that means their fight against the tiger mosquito has become a race against time.Each evening at 1830 UTC, DW's editors send out a selection of the day's hard news and quality feature journalism. You can sign up to receive it directly here.