Explained | Why are locally acquired cases of malaria in the U.S. of concern?

According to the CDC, suspected or confirmed locally acquired malaria is a public health emergency.

July 01, 2023 02:05 pm | Updated 09:25 pm IST

A 2014 photo from the CDC shows a feeding female Anopheles mosquito.

A 2014 photo from the CDC shows a feeding female Anopheles mosquito. | Photo Credit: CDC via AP

The story so far: TheUnited States’ Centres for Disease Control and Prevention (CDC) has identified locally acquired malaria cases in Florida and Texas in the last two months. This is the first time that such malaria cases have been reported from the U.S. in the last twenty years.

The CDC has also raised concerns about a potential rise in imported malaria cases with increased international travel over the summer.

What is a locally acquired malaria case?

Locally acquired malaria denotes cases where the disease presents in patients with no travel history, indicating that it has been acquired within their geographical area. Although malaria does not occur in all warm climates, according to the CDC, most cases are found in parts of Africa, Central and South America, the Caribbean, Oceania, and South, West, and Southeast Asia. A locally acquired case would mean that the mosquito transmitting the disease first bit a person carrying the malaria-causing parasite and then another person, thus transmitting the disease locally.

What are the recent developments in the U.S.?

The CDC in an advisory issued on June 26 recommended that medical health professionals consider a malaria diagnosis for patients with fever of unknown origin, regardless of their travel history. The agency also said that patients suspected of having malaria should be urgently evaluated in an appropriate medical facility.

Florida has reported a total of four locally acquired malaria cases this year, with two of them reported as recently as between June 18 and 24, 2023 from Sarasota County. The State also reported 23 malaria cases in 2023 which were associated with international travel.

One case of locally acquired malaria has been identified in Cameron County, Texas.

Why is this concerning?

According to the CDC, suspected or confirmed locally acquired malaria is a public health emergency.

Malaria is a potentially fatal disease caused by a protozoan from the Plasmodium genus. This is usually transmitted through the bite of an Anopheles mosquito, and almost all cases of malaria in the U.S. are found in people who have a history of international travel. Locally acquired cases of malaria in the country are rare. In fact, Texas recorded its last locally acquired malaria case in 1994— before it resurfaced this year.

The parasite identified in tlocally acquired cases across Texas and Florida is Plasmodium vivax. Although not the worst among the types, P. vivax is the most common type of parasite that causes malaria in humans. Although most cases caused by this type are of comparatively lower intensity, it can still cause cerebral malaria, renal failure, acute respiratory distress, and shock in some patients.

Plasmodiumfalciparum is responsible for the deadliest type of malaria in humans.

Malaria usually starts off with flu-like symptoms that include fever, chills, nausea, and sweats, but can lead to more severe symptoms like disorientation, seizures and other neurological symptoms, low red blood cell counts (anaemia), acute respiratory distress syndrome, and kidney damage, if left untreated or unsupervised.

According to Colin Carlson, a biologist studying the relationship between global climate change, biodiversity loss, and emerging infectious diseases, it is “somewhat likely” that climate change contributed to the presence of malaria cases in the U.S. However, Dr. Carlson also says that southern U.S. states meet the minimum conditions of a warm climate needed for malaria, even without climate change.

Malaria was, in fact, endemic in large parts of the U.S. until the 1950s when it was eradicated due to “increased urbanisation and improved socioeconomic conditions, which resulted in decreased human-vector contact, increased access to medical care and effective treatment, and reduced Anopheles populations”, according to CDC.

What can U.S. residents do?

The CDC recommends that U.S. citizens prevent mosquito bites and control the presence of mosquitos in their houses.If people are travelling to a country where malaria is endemic, the agency recommends that they learn about the health risks and precautions associated with malaria and monitor symptoms if they show up. CDC also recommends getting medical attention in case of symptoms.

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