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US Witnesses First Cases of Locally Acquired Malaria in Two Decades

cdc malaria warning

The Centers for Disease Control and Prevention (CDC) has recently issued a public health alert, a move brought about by the detection of locally acquired malaria cases in Florida and Texas. This situation marks an unprecedented event in the last two decades, specifically since it’s the first time that such local infections of this disease have been detected in the United States in the last 20 years.

Malaria, a disease well-known in regions with tropical and subtropical climates, was thought to be well-managed and under control within the U.S., making this recent development quite alarming.

Details on the Newly Emerged Cases

In the span of the past two months, five cases of malaria have been identified that were contracted locally – four in the state of Florida and one in Texas. This number might seem small at first glance, but the fact that these individuals contracted the disease within U.S. borders is what is causing significant concern among health officials. Instances of such infections have been absent from the country’s disease surveillance records since as far back as 2003.

Looking Back: Malaria’s Footprint in the US

While it might come as a surprise to some, the United States is not entirely unfamiliar with malaria. In fact, before the global health crisis brought on by the COVID-19 pandemic, the country was registering about 2,000 malaria cases every year. However, a crucial detail in this context is that these cases in the U.S. are almost always discovered in people who have recently traveled outside of the country, particularly to regions where malaria transmission is endemic and more commonplace.

The recent infections identified in Florida and Texas being caught locally suggest that mosquitoes within these areas have acquired the parasite and managed to spread it amongst the local population.

Revisiting Malaria: A Potentially Deadly Foe

It’s essential to understand that malaria was once a widely prevalent disease in the U.S. During the first half of the 20th century, the country was grappling with this health threat, until a comprehensive eradication program was put into place. The National Malaria Eradication Program, implemented during the 40s and 50s, eventually managed to eliminate the disease’s endemic status in the country.

Today, the CDC categorizes malaria as a “medical emergency,” stressing its potential to be fatal, particularly among vulnerable groups such as children under five and pregnant women. Symptoms of the disease can be wide-ranging, from mild to life-threatening. They can often mimic flu-like symptoms and can also cause an enlarged spleen, enlarged liver, or mild jaundice.

Recognizing a “Malaria Attack”

One of the distinguishing symptoms of malaria is what’s commonly referred to as a “malaria attack”. This condition is characterized by an infected individual experiencing a distinct period of illness that lasts six to 10 hours.

These malaria attacks are defined by three sequential stages: a cold stage, which is dominated by chills and shivering; a hot phase, marked by fever, headaches, vomiting, and potentially seizures in children; and a sweating stage, in which the patient’s body temperature returns to normal. These stages recur throughout the course of the infection, leading to a cyclical pattern of illness.

The Role of P. vivax in the Current Cases

Interestingly, of the four kinds of malaria that can affect humans, the cases detected recently in the U.S. have all been caused by the parasite Plasmodium vivax (P. vivax). Among the more than 200 species of mosquitoes that inhabit the continental U.S. and its territories, there are only two species that are known to be capable of carrying and spreading the P. vivax parasite.

The Challenge of Early Detection and Effective Treatment

Detecting the P. vivax infection early can be quite a challenge. The parasite takes about 10 to 15 days to develop inside of a mosquito before it can become transmissible, meaning that the potential spread of malaria may not be immediately noticeable, especially if the initial symptoms are ignored or misinterpreted.

The conventional anti-malaria drug, chloroquine, is effective against infections caused by P. vivax, but the treatment does not end here. Infections associated with this parasite will likely require additional treatment due to the unique life-cycle of P. vivax.

Dealing with the Side Effects of Malaria Treatment

P. vivax is one of two forms of malaria that can remain dormant in the liver, potentially causing recurring illness for months or even years. Therefore, another drug—such as one called primaquine—is often needed to target and eliminate the dormant parasite in the liver.

This course of treatment, while necessary, has its own set of complications. Side effects of primaquine can include fatigue; a weak pulse; discoloration of the skin and eyes; seizures; confusion; and blurred vision.

Moreover, primaquine should not be administered to people who have a genetic condition known as G6PD deficiency. The drug can lead to damage of red cells in these individuals, causing a severe form of anemia. The issue here is that many people aren’t aware they have G6PD deficiency until they start a treatment like primaquine and encounter complications.

Pinpointing the Causes of the Recent Outbreak

In their attempt to understand the sudden emergence of locally transmitted malaria, the CDC has suggested a few potential contributing factors. Increased international travel brought on by the summer season, coupled with the onset of the hurricane season which leaves more standing water—prime mosquito breeding grounds—may have contributed to these infections.

Greater Implications: A Gateway to Other Diseases?

One overarching concern is that these malaria cases could potentially signal the spread of other mosquito-borne diseases like dengue, the Zika virus, West Nile virus, and the Chikungunya virus. These diseases, like malaria, can cause significant health issues and strain public health resources.

Preventive Measures and CDC Recommendations

To combat this threat and reduce the chance of becoming infected, individuals can opt for clothing that is already treated with a synthetic repellent and insecticide called permethrin. They can also use standard mosquito repellents to protect their exposed skin.

Furthermore, the CDC has issued advice to healthcare professionals. They have urged clinicians to consider malaria when treating patients presenting with a fever of unknown origin, irrespective of their recent travel history. Gathering a detailed travel history from patients has also been recommended, as this can assist in making a correct diagnosis.


Source: Centers for Disease Control and Prevention. (2023). Health Advisory: First locally transmitted malaria cases detected in US in decades. Retrieved June 28, 2023, from https://emergency.cdc.gov/han/2023/han00494.asp


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