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U.S. Public Health Officials Warn Frontline Providers to Watch for Malaria Cases

By Dorothy Brooks, Special for

Frontline healthcare providers likely will confront seasonal surges in cases of COVID-19, respiratory syncytial virus, influenza, and other common respiratory diseases as temperatures cool. Meanwhile, they also need to be concerned with a threat associated with current warm temperatures.

For the first time in decades, cases of locally acquired malaria have turned up in Florida, Texas, and Maryland. Thus, U.S. public health officials are urging clinicians to raise their suspicion levels for the mosquito-borne illness when patients present with fever with an unknown etiology, even if the patients have not traveled recently to a country where malaria is endemic.

Sarasota Memorial Hospital in Florida saw the first of five cases of locally acquired malaria that it treated in early May, explains Manuel Gordillo, MD, the hospital’s director of infection control. “That was a 64-year-old male who came in with fever, nausea, and abdominal pain,” he reports.

Clinicians did not suspect malaria at first, but the patient was sick enough that he needed to be hospitalized. “The admitting team then got a call from the lab because the tech who looked at a blood smear that was taken from the patient saw parasites that resembled malaria,” Gordillo recalls. “This is a call that we get once or twice a year, usually regarding a patient who has traveled to an area with endemic malaria, so we were expecting to see someone like that. But when we went to see this person, he was homeless and never traveled, so we were shocked.”

Educate Clinicians

At this point, treatment for the patient was initiated using the antimalarial agent Coartem (a combination of artemether and lumefantrine), and infectious disease staff immediately contacted the health department. Staff knew that with a case of locally acquired disease, there likely would be other cases. “Also, I personally went and talked to all of the emergency medicine physicians and other providers about the case and told them to be on the lookout for other cases,” Gordillo says.

Sure enough, two other cases in the region soon turned up in other hospitals, and Sarasota Memorial saw four additional cases, too. Gordillo acknowledges it is difficult for clinicians to differentiate malaria from other diseases with similar symptoms.

“There are so many people who come into the ED with a febrile illness and get admitted,” he says. “All of our cases also had gastrointestinal symptoms, such as diarrhea and abdominal pain, so they got admitted as gastroenteritis or as a febrile illness of unknown etiology.”

While it is important for clinicians to consider malaria so that they will order appropriate blood smear testing, a diagnosis typically is confirmed by the lab. “All of our cases [were confirmed] that way,” Gordillo says. “Within hours, the laboratorians made the call.”

The diagnosis was considerably delayed for one patient with malaria who presented to a different hospital in the region that did not employ experienced laboratorians in house. However, emergency clinicians did send a blood smear to an outside lab where the diagnosis was confirmed several days later. By that time, the patient had been treated with antibiotics for suspected pneumonia and was no longer at the hospital. “They had to contact the health department to track the patient down, and they eventually were able to provide treatment,” Gordillo shares.

All patients requiring treatment for locally acquired malaria in Florida have reportedly recovered from the disease and are feeling well.

All seven of the locally acquired malaria cases in Sarasota County, FL, and the single case that turned up in Cameron County, TX, were attributed to Plasmodium vivax parasites, the most common form of malaria seen in the United States, according to the CDC. Experts from that agency discussed these cases with clinicians in a presentation on July 20.

However, a more recent case discovered in a Maryland resident in August was caused by Plasmodium falciparum parasites, which are less common in the United States, but are associated with more severe disease, according to the CDC. The patient reportedly has been treated and discharged home to recover from the illness.

Prioritize Treatment

Adam Rowh, MD, an epidemic intelligence service officer at the CDC and a member of the agency’s medical countermeasures team malaria response, discussed how malaria develops after an infected mosquito injects parasites into a human. He explained the parasites travel to the liver within hours, where they undergo initial replication.

“This asymptomatic phase of replication in the liver lasts an average of one to two weeks for most Plasmodium parasites, but [can] last longer,” Rowh said during the July 20 presentation.

He noted some long incubation periods have been observed, including instances where cases of malaria have developed months to years after travelers have visited countries where malaria is endemic.

“After an initial liver phase, the parasites are released into the blood, causing blood stage disease. This is when people will first have malaria symptoms, which are most commonly fever, headache, and myalgias,” Rowh explained. “As the parasites replicate in the blood and reach higher parasite densities, this can lead to more severe disease.”

Also, Rowh noted parasites in the blood will develop into gametocytes, a form of parasite that can infect mosquitoes, leading to further transmission of malaria. “Without prompt treatment, an initially nonsevere case of malaria can progress to severe malaria, which mimics other severe medical illnesses like bacterial sepsis,” he said.

Rowh noted there are two laboratory tests that can be used to guide clinical decision-making: a blood smear and a rapid diagnostic test. However, he said the gold standard for diagnosis is microscopic examination of a blood smear, which can be used to identify the species of Plasmodium, as well as parasite density.

“The rapid diagnostic test can be used to decrease the time to diagnosis and treatment, but it is not a replacement for the blood smear because it does not provide parasite density,” Rowh said. “There are numerous resources available to help [clinicians] manage a patient with malaria, including a CDC consult, but all require a clinician to consider malaria as a possibility and perform diagnostic setting.”

Gordillo agrees with this advice, reiterating to his emergency medicine colleagues to order a blood smear for any patient who presents with a fever with an unclear etiology. “We’ve been taking a lot of blood smears in our hospital,” Gordillo says.

For more information about diagnosing and treating malaria, visit the CDC’s malaria page here. For more information on this and related subjects, be sure to read the latest issues of ED Management, Emergency Medicine Reports, Hospital Infection Control & Prevention, and Infectious Disease Alert.