Above, CBS News makes climate connection to recent malaria outbreak.
In late May, Sarasota County, Florida, health officials confirmed they had identified a case of locally transmitted malaria. In mid-June, they confirmed the second. On June 23, Texas joined in: its state health department announced it had confirmed a case of local malaria transmission in Cameron County.
This is all highly unusual. The US hasn’t documented a locally acquired malaria case in 20 years.
Although about 2,000 people infected with malaria turn up in the US health care system every year, those cases are all linked to travel outside the US. Neither those involved in the Florida cases nor the Texas case had traveled. That means in both states, the infection was acquired within US borders.
Experts say the three cases shouldn’t warrant panic about widespread malaria transmission in the US. But it does warrant asking some questions, and being wary of the threat of more local transmission. Mosquitoes can infect multiple people before a full-on outbreak is even identified — so more cases could be out there.
Even if this turns out not to be widespread, it’s a good reminder: Malaria could make a comeback in the US, and we — and our public health infrastructure — ought to be prepared. This is especially true as a changing climate and shifting weather patterns increasingly drive mosquito migration into new places worldwide, allowing malaria to settle in where it hasn’t before.
Although malaria was eradicated from the United States in the early 1950s, it had once been a prevalent disease, especially prior to the 1880s.2 Through-out the nineteenth century, malaria affected most populated regions in the United States, significantly undermining the health of the population and the U.S. economy. Above all, malaria was one of the country’s leading causes of death. According to the U.S. Census Bureau, 45.7 out of every 1,000 deaths resulted from malarial fevers in 1850. For infants, children under age five, and people in southern states—all of whom were at the highest risk of contracting malaria—the corresponding number was as high as that for current malaria-endemic countries.3Malaria also ravaged the troops of the Union Army, its fevers killing about 10,000 recruits during the U.S. Civil War.4
In Florida, Texas, and other parts of the South, a flower pot or a tire sitting in a yard could house unwelcome guests: mosquito eggs of the species Aedes aegypti.
It’s the type of mosquito that transmits dengue, Zika, and yellow fever.
Roxanne Connelly of the Centers for Disease Control and Prevention is an expert in mosquito-borne diseases.
“These eggs are drought resistant and they can survive up to several months,” she says. “Once those eggs are covered with water, whether it’s from rainfall or a sprinkler, the eggs will hatch into larvae.”
Aedes aegypti is sensitive to cold temperatures — as eggs and adults. So they cannot survive the winter in much of the country.
But Connelly says that as the climate warms, these mosquitoes may establish populations farther north, for example in Nevada, Utah, and Nebraska.
“In all three of those places, the mosquito has been detected for a few years in a row,” Connelly says. “So it seems that there are some places outside of where you would expect it where it is becoming established.”
Mosquitoes can only spread Zika or dengue fever after biting an infected person. So the species’ expanding range will not necessarily lead to outbreaks.
But Connelly says the public should be aware of the growing risks.
Here’s another case of “Welcome to the party, pal!”
Now people in Africa might start getting more effective malaria vaccines and/or treatment.