In the 1970's and '80's, Aedes albopictus mosquitoes came to the U.S. through the used tire trade. These stowaway insects, also known as Asian tiger mosquitoes, can carry viruses like dengue, Zika and chikungunya. They quickly adapted to city life in the southern, eastern and western U.S.
Since then, due to globalization and climate change, insects and the diseases they carry are spreading more widely around the world.
At a two-day workshop this week at the National Academies of Science, Engineering and Medicine in Washington, D.C., global public health experts warned that countries like the U.S. are not ready for this looming threat.
"If we don't do anything, which is basically what we're doing right now, it's going to get worse," Tom Scott, a medical entomologist and professor emeritus at UC Davis, said during the workshop. "The damage from inaction is enormous, it's unacceptable. It's unethical."
The workshop focused on arboviral threats, which are mosquito- and tick-borne viruses that can cause harm to humans.
Tropical diseases that were once considered far away from the U.S. are becoming a presence. This year, the U.S. saw locally transmitted cases of malaria and a skin disease from tropical parasites. A Zika outbreak occurred in Florida and Texas in 2016-2017 and dengue has spread locally in the U.S. every year for over a decade.
The signs have long been obvious to tropical disease researchers.
"We don't pay enough attention in the United States to what is going on in other countries. We just kind of watch it spread and we don't prepare ourselves for that virus potentially coming to the U.S.," Laura Kramer, director of the Arbovirus Laboratory at State University of New York at Albany, told the workshop attendees. "That happened with Zika, chikungunya and West Nile."
Researchers at the workshop said countries like the U.S. can expect more tropical diseases to come – and should be preparing for them. Global warming is expanding the range of some tropical insects and diseases.
But the U.S. has lost a lot of its capacity to track insects. In 1927, every state had its own entomologist working to control insect populations and malaria, Erin Staples, a medical epidemiologist with the Centers for Disease Control and Prevention, said during the workshop.
"Where are we now in 2022? We've got sixteen state entomologists." That means the nation's ability to monitor viruses like West Nile is sparse. "We're not getting great information because we haven't maintained our infrastructure," Staples said.
So what should the U.S. be doing?
Public health researchers say Singapore is a shining example of mosquito control. The country has cut the number of mosquitoes – vectors for viruses such as dengue and Zika – by cleaning up the city environment and teaching good practices from a very young age. "My four-year-old daughter will come home and tell me about vector control because she learned it in kindergarten," said Lee-Ching Ng, with the Singapore government's Environmental Health Institute.
Singapore also has a big, expensive surveillance program, which tracks dengue cases by neighborhood and sends phone alerts when cases are high. And residents in Singapore can be fined or jailed for harboring mosquito breeding sites at home. Peter Daszak, president of the nonprofit EcoHealth Alliance, described Singapore's approach as "the carrot and the stick."
"There is a willingness to [take action in Singapore,] and they've done it and it works," he said. Still, that approach may not work in other countries such as the U.S., "where we're seeing pushback after COVID against all forms of intervention to people's personal freedom," he said.
Other tools could work, such as vaccines – which currently exist against some of these diseases. And designing cities in ways that are mosquito-proof.
