What's the deadliest animal in the world?  A tiger?  A great white shark?  A poisonous snake?  Nope.  The most dangerous animal on Earth weighs about 2/1000 of a gram, is smaller than an M&M, and could be knocked silly by a raindrop.  It's the mosquito.

Mosquitoes, obviously, can't eat you the way a shark or tiger could.  They act as "vectors" for a number of diseases, one of which is malaria.  When a mosquito of the species Anopheles bites you, it extracts blood as a meal and leaves some of its saliva.  The saliva harbors any of a number of disease-causing organisms.  In the case of malaria, it's a single-celled parasite in the genus Plasmodium.  There were over 240 million cases of the disease (with 627,000 deaths) in 2020, almost all from mosquito bites.

The United States has, in the past, had its own problems with malaria.  In fact, a 1933 survey found that up to thirty percent of local populations in the Tennessee River Valley were affected.  The disease was also common in WWII war zones.  Malaria became such a concern that the CDC was established primarily to combat it.

(Note: Back then, "CDC" stood for "Communicable Disease Center."  Now it stands for "Centers for Disease Control and Prevention.")

The CDC and health agencies of thirteen Southeastern states instituted the National Malaria Eradication Program in 1947.  By the end of 1949, over 4,650,000 homes were sprayed with insecticide.

This had an immediate effect.  In 1947, 15,000 new cases were reported.  The next year, it was down to 2,000.  By the end of the year after that, malaria was considered eradicated in the United States.  This public health miracle happened through the widespread implementation of insecticides, drainage programs, and the installation of door and window screens.

In the age of air-conditioning, you might consider malaria to be an issue for the Amazon rainforest or sub-Saharan Africa.  In recent weeks, however, five cases have been reported as originating locally in Florida and Texas.  Local transmission hasn't occurred in the U.S. for twenty years.  Almost all American malaria victims contracted the infection when they were traveling abroad.

There are several hypotheses as to why we are seeing new cases of local malaria in the United States.  The conventional wisdom put forth by many experts points to warmer temperatures caused by climate change.  Hotter weather and increased rainfall, indeed, could lead to wider spread of malaria and other tropical diseases.  Mosquitoes breed best in the heat (as long as there's a water source to lay eggs) and are rendered inactive by cold.

Others suggest that the recent cases, caused by a type of Plasmodium (P. vivax) that causes less severe symptoms, may not have been recognized as being signs of malaria by the victims or their medical providers until they really got ill.

(Note: Despite having less severe symptoms, the CDC considers any case of malaria a medical emergency which must be treated immediately.)

Perhaps the malaria cases in Texas and Florida may have been discovered because COVID raised people's awareness regarding flu-like illnesses.  Those who are feeling sick may be more likely to present to a medical professional, only to find they have malaria instead of COVID.

An alternative hypothesis you won't hear about is the possibility that aliens crossing the border, many of whom come from countries where malaria is common, may be carrying the parasite.

This makes a lot of sense if you think about it.  Look at a CDC map of where malaria is endemic (always there), and you'll see many nations that are sending mass numbers of people across our southern border.  Millions from Central America, Haiti, Venezuela, and other endemic regions have entered our country, and you can bet they haven't been tested for malaria.  As a matter of fact, illegal aliens don't undergo a medical screening at all prior to entry into the United States (unless, I would think, they're visibly sick).

How would an alien bring malaria into the U.S.?  Well, many malaria-sufferers are carriers.  The Plasmodium organism can live dormant in the liver for a period of time.  It's only when the parasite enters red blood cells that the patient becomes obviously ill.

If carriers get bitten by mosquitoes after they arrive in the United States, the now infected mosquitoes can transmit the disease locally.  The more carriers in the population, the more likely a mosquito will eventually bite one and carry the organism to other people.

Luckily, malaria isn't passed directly from human to human through the air or casual contact.  There are effective treatments available (including, surprise, hydroxychloroquine).  The length of treatment depends on the type of malaria, the region where infection occurred, the patient's age, pregnancy, and the degree of sickness.  If treated early, full recovery can be expected.

There's no reason to believe that a major outbreak of malaria will hit the U.S., but let's not hide what might be a contributing factor to its reappearance.  It's just one of the risks of having an open border.

Image via Pixnio.