Malaria Is Making a Comeback in the US! What Do Scientists Say?

The recent cases of malaria identified in Texas and Florida may have you wondering if our country is turning into a place for tropical diseases typically associated with foreign travel. These cases—seven in Florida, one in Texas, and one in Maryland—were of people who hadn’t recently traveled outside the US. These are the first cases of locally acquired malaria since eight cases occurred in Florida in 2003.

The truth is that the risk of malaria in the US has never gone away, scientists say. These cases are the latest reminder that precautions and vigilance are necessary to ensure that mosquito-borne diseases eradicated from the US don’t come back and illnesses caused by the ones already here don’t grow worse.

Back in the 1950s, malaria was a stubborn plague in the US, especially in the Southwest. Many of the factors that contribute to the spread of malaria haven’t changed much since then. The Anopheles mosquitoes that spread the disease still thrive in different parts of the country, and states that receive lots of tourists from countries where malaria is endemic continue to experience warm, wet weather that favors mosquito reproduction.

What is malaria, and how serious is it?

Malaria is a serious disease caused by a parasite that’s commonly transmitted by the Anopheles species of mosquito. People who get it are typically very sick, experiencing symptoms that include a fever and flu-like illness, such as headaches, fatigue, nausea, shaking chills, diarrhea, vomiting, and muscle aches.

Malaria can also cause jaundice, where the eyes and skin become yellow due to fewer red blood cells, and anemia (low blood cell count). Symptoms generally begin 7–10 days after infection but could start as much as a year later.

There are five types of malaria that infect humans. Of those five, P. vivax and P. falciparum are responsible for nearly all of the estimated 240 million cases that occurred globally in 2021. P. falciparum is far more dangerous, causing the majority of the 619,000 global deaths from malaria in 2021.

What’s the current situation in the US?

While there are about 2,000 cases of malaria in the US each year, nearly all of them occur in people who travel from South Asia or sub-Saharan Africa. According to Amesh Adalja, an infectious disease, biosecurity, and pandemic scientist at Johns Hopkins University, “malaria and mosquito-borne illnesses, including yellow fever, were once often spread in the US”.

He also points out that there isn’t an insurmountable barrier for these mosquito diseases to be able to appear in the US, and that what really drove them back was very effective vector control and making areas inhospitable for these flying insects in terms of standing water.

That’s why these new cases of malaria in the US weren’t a surprise to infectious disease experts. Moreover, Peter Hotez, professor at and dean of the National School of Tropical Medicine in Houston, calls these cases “predictable and predicted”.

According to him, the reason there’s an increasing incidence of malaria in the US is because of a confluence of a couple of factors, which include human migrations, urbanization, poverty, and climate change. “Those are all converging, and because of this mix of forces, we’re seeing not only malaria but also West Nile, typhus, dengue fever, chikungunya, Chagas disease, Zika, and worm infections,” Hotez says.

Moreover, we’re a much more interconnected world, and with increased travel and other climate-driven features that are making spreading and transmission easier for viruses and diseases, it’s not a massive surprise that malaria in the US is becoming a threat.

The public health infrastructure may be far more fragile than we realize

Even with these new cases of malaria in the US, scientists say that something would have to go very wrong for the disease to become endemic in our country. It’s perhaps the understatement of the year to say the US isn’t immune to “things going seriously wrong”.

In fact, recent history has shown us that the country’s public health infrastructure, which millions of Americans rely on to catch and treat invasive infectious diseases, is far more brittle than many realize.

But how vulnerable is the nation to a malaria resurgence? Here’s what our country has going for it—and against it—when it comes to malaria risk.

The US has some weapons in its favor in the fight against a malaria comeback

One key factor our country has going for it is that it has already eliminated malaria. According to scientists, while malaria in the US still represents a threat, the centralized focus on getting rid of both the parasites that cause it and their mosquito hosts’ breeding grounds has really defeated the disease.

Contrary to popular belief, it’s also helpful that when people in the US get malaria, they tend to get sick. When infections are obvious, they are easier to detect, treat, and contain. In countries where malaria is more common, the infection cases are more asymptomatic due to greater immunity to the disease, which makes outbreaks more difficult to spot.

According to experts, we don’t have this sort of immunity as a population. So when cases of malaria in the US occur, we see them. And while the US health care and public health systems are shaken by problems that don’t affect other developed nations, compared with poorer countries, these US systems have more capacity to fight against malaria transmission when a case occurs.

Moreover, when it comes to malaria in the US, the country has good, if not uneven, capacity for controlling mosquito populations, which is a key factor in reducing human risk for infections they spread.

The Anopheles mosquitoes that transmit malaria are nighttime biters, so the broad prevalence of air conditioning and window screens in the US provides an extra measure of security against the broad spread of malaria.

Travel, social vulnerability, and climate change create some undeniable risk

Climate change is one of the main factors making malaria in the US a real threat. As a result, our country gets warmer, making it more hospitable to the parasite and its Anopheles mosquito vector.

The summer of 2023, in particular, brought a warming climate with it that has driven record levels of flooding and rain in the US. When high rainfall occurs near sea level, a lot of water gets close to the ground’s surface, which creates the perfect conditions for mosquito breeding.

According to scientists, rising air temperatures could mean an expansion of malaria in the US, well beyond the Southeastern states and into other parts of the country. In a recent analysis, it turned out that 32 US states had Anopheles mosquitoes capable of spreading malaria.

Should you worry about catching malaria in the US?

In the wake of the COVID-19 pandemic, it shouldn’t be a surprise that malaria in the US is becoming a real threat. Also, it’s commonly known that infectious diseases outside the US pose a risk inside the country. The same is true for malaria.

However, the risk of catching malaria in the US hasn’t significantly increased from several weeks ago, even in the areas where these cases occurred.

In order to prevent mosquito bites, make sure you use mosquito repellent when you’ll be around insects (Amazon.com has plenty of options). Experts also advise wearing longer clothes to cover up as much skin as possible.

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