Dengue typically comes in cycles, hitting some areas harder in different years. People remain susceptible to the other strains after being infected with one and it is largely an urban disease with mosquitoes breeding in stagnant water.
Laos and Singapore have experienced their worst outbreaks in recent history this season. Thailand has also struggled with a large number of patients. Cases have also been reported in recent years outside tropical regions, including in the US and Europe.
Vietnam has logged lower numbers this year overall, but the country’s highest dengue rate is in the province where Yen is conducting her work.
At the area’s main hospital in Nha Trang, director of infectious diseases Nguyen Dong said 75 of the 86 patients crammed into the open-air ward are infected with the virus.
Before jabbing his fingers into the stomach of one seriously ill patient to check for pain, he talks about how the dengue season has become much longer in recent years. Despite the Vietnamese government’s increased education campaigns and resources, the disease continues to overwhelm the hospital.
If the experiment going on just a short boat ride away from the hospital is successful, it will eventually be expanded across the city and the entire province.
The 3,500 people on Tri Nguyen Island grew accustomed to what would be a bizarre scene almost anywhere else: For five months, community workers went house-to-house in the raging heat, releasing cups of newborn mosquitoes and the residents were happy to have them.
“We do not kill the mosquitoes. We let them bite,” fisherman Tran To said. “The Wolbachia living in the house [mosquito] is like a doctor in the house. They may bite, but they stop dengue.”
Specimens collected from traps are taken back to the lab for analysis to determine how well Wolbachia mosquitoes are infiltrating the native population.
The strain of bacteria used on the island blocks dengue 100 percent, but it is also the hardest to sustain. At one point, 90 percent of the mosquitoes were infected, but the rate dropped to about 65 percent after the last batch was released in early September. A similar decrease occurred in Australia as well and scientists switched to other Wolbachia strains that thrive better in the wild, but have lesser dengue-blocking abilities.
The job is sure to keep Yen busy in her little mosquito lab, complete with doors covered by long overlapping netting. While she professes to adore these pests nurtured by her own blood, she has a much stronger motivation for working with them: Dengue nearly claimed her own life many years ago and her career has been devoted to sparing others the same fate.
“I love them, when I need them,” she said.