Health experts urge clinicians to 'remain vigilant' about malaria cases in new commentary

Following the identification of the first locally acquired malaria cases in the US in 20 years, experts warn in an Annals of Internal Medicine commentary that nations could see worrisome resurgences of the disease without increased efforts to improve global detection and treatment.

As worsening climate change and increased global travel create ideal conditions for a resurgence of malaria in areas where it has long been eradicated, clinicians must be vigilant of the disease's symptoms and act swiftly once cases are detected, health experts warn in a new commentary published in the Annals of Internal Medicine.

In the last few months, Florida and Texas have reported eight malaria cases—the first locally acquired cases of the mosquito-borne disease in the United States since 2003.

While no new locally acquired cases have been reported in the US since July 13, the ongoing threat of rising temperatures, extreme weather events, and the widespread presence of mosquitos capable of transmitting the parasite that causes malaria create ample opportunities for local transmission of malaria and may foreshadow future outbreaks in nonendemic countries, the authors write.

"Between increased international travel since the end of the COVID-19 pandemic, global warming, and evidence of geographic expansion of many mosquito populations, the potential for the introduction and spread of vector-borne diseases such as malaria, dengue, and chikungunya is increasing," says Dr. Davidson Hamer, corresponding author of the commentary, professor of global health and medicine at Boston University School of Public Health and BU Chobanian & Avedisian School of Medicine, and an attending physician at Boston Medical Center. The commentary was coauthored by researchers at the Center for Disease Control & Prevention, IRCCS Sacro Cuore Don Calabria Hospital in Negrar, Italy; and McGill University Health Center in Montreal, Canada.

Once endemic in the US, malaria had been eliminated in the country since the 1950s, except for about 2,000 cases each year that were acquired from individuals traveling overseas. The disease often causes flulike symptoms, but it can cause serious illness and death if it is not treated.

Malaria thrives in warmer climates and is most prevalent in parts of Central and South America, Africa, Asia, Eastern Europe, and the South Pacific. In recent years, global advances in malaria control have stalled, and internationally acquired malaria cases in the US have been increasing steadily since the 1970s.

Thus, malaria cases in the US are not necessarily rarities, or "zebra" diagnoses, and a clinician's ability to rapidly suspect, diagnose, and treat malaria is life-saving and "a first line of defense against local transmission," the authors write. Access to quality and affordable testing is also crucial.

"Clinicians need to take a travel history from their patients but also need to be aware of the potential for local transmission of pathogens that may not have been seen in their communities for decades," Dr. Hamer says. "We have good diagnostic tools available for diseases such as malaria, but unless a clinician thinks about this possible diagnosis, it will be missed."

He is encouraged by the fact that no additional locally acquired transmission has been confirmed in the US since mid-July. "The public health authorities in Florida, with help from national partners at the CDC, have worked together to identify and treat patients with locally acquired malaria and have made efforts to reduce the competent vector population. These measures are working and appear to have limited further spread of this outbreak."