Fact check: False claim that most scientists blamed malaria on dirt in 1900

The claim: In 1900, only two doctors, Walter Reed and George Goethals, thought malaria was transmitted by mosquitoes

Malaria is a potentially fatal illness that typically causes acute sickness, shaking chills and fever, according to Mayo Clinic. It is caused by parasites that are transmitted to humans through mosquito bites.

Some social media posts are attempting to rewrite the history of malaria while presenting a commentary on the legitimacy of scientific consensus.

"99% of scientists agreed dirt caused malaria in 1900," reads a June 7 Facebook post that was shared 1,500 times in a week. "Just 2 doctors, Walter Reed and George Goethals, didn't. They thought mosquitos were the culprits. They were right. All the others were wrong."

The claim also spread on Twitter.

But this is revisionist history.

The parasite that causes malaria was discovered in 1880, and multiple researchers contributed to connecting the illness with mosquitoes over the next two decades.

By 1900, the fact that mosquitoes spread the disease had been documented and was supported by far more than two scientists, as evidenced by multiple historical accounts. Walter Reed and George Goethals were not involved in proving that malaria was transmitted by mosquitoes, according to a Johns Hopkins University historian.

USA TODAY reached out to the Facebook users who shared the post for comment. The Twitter user could not be reached.

Follow us on Facebook! Like our page to get updates throughout the day on our latest debunks

Walter Reed showed yellow fever, not malaria, spread by mosquitoes

Neither Walter Reed nor George Goethals were involved in proving that malaria is spread by mosquitoes, according to Randall Packard, a professor at Johns Hopkins University who authored a book on the history of malaria.

Reed was an American doctor who, with the help of colleagues, proved that yellow fever was spread by mosquitoes. This occurred after malaria had already been shown to be transmitted by mosquitoes, Packard told USA TODAY in an email.

Goethals was a U.S. Army officer who helped build the Panama Canal, according to Encyclopedia Britanica. He was not involved in proving malaria came from mosquitoes, Packard said.

And even before the discovery that malaria was spread by mosquitoes, "dirt" was not widely believed to cause malaria – contrary to the claim in the post.

"I really do not know who he is referring to when he says doctors believed dirt was the cause of malaria," Packard said. "Miasmas arising from moist land or swamps were the primary theory before the discovery of the role of mosquitoes."

"Miasmas" refers to toxic vapor or "bad air" thought to cause a variety of diseases before the discovery of microbial pathogens.

Fact check: Vaccination helped eradicate smallpox

Multiple researchers helped establish that malaria came from mosquitoes prior to 1900

Rather than being promoted by two rogue doctors in 1900, the idea that malaria was a microbe transmitted by mosquitoes was fostered by multiple scientists over decades.

"There was a cohort of people working on malaria, not just one or two people. And it was international," Ellen Amster, a medical historian and associate professor at McMaster University, told USA TODAY in an email.

By 1900, the mosquito's role was in fact widely embraced.

Scottish physician Patrick Manson published a paper that year that opened by saying, "The theory that the malaria parasite is transmitted from man to man by particular species of mosquito is now accepted by all biologists and medical men who have given adequate attention to the subject."

This is proven out by multiple original research papers, articles and correspondence connecting malaria to mosquitoes from the year 1900 or prior that are still publicly available.

French doctor Charles Louis Alphonse Laveran was among those who suspected that malaria was caused by a microbe and not miasmas. He discovered the malaria parasite in patient blood samples in 1880, according to an Institute of Medicine book on the subject.

For his discovery, he was awarded a prize by the Academy of Sciences in 1889 and a Nobel Prize in 1907, according to The Nobel Prize website.

Laveran suspected the parasites may have been transmitted to humans by mosquitoes but did not confirm this himself, according to the CDC.

An American doctor, Albert King, also proposed the hypothesis that malaria was transmitted by mosquitoes in the early 1880s, according to an article published in Science.

British doctor Ronald Ross discovered the malaria parasite in the stomach of a dissected mosquito in 1897, according to a speech delivered when he was later awarded The Nobel Prize for this work.

In 1898, Italian scientists, including Amico Bignami, Giovanni Battista Grassi and Giuseppe Bastianelli, showed definitively that mosquitoes transmitted the parasite to humans, according to a history of the subject published in the journal, Parasites & Vectors.

Fact check: Claim about growing number of diseases exaggerates, omits context

Our rating: False

Based on our research, we rate FALSE the claim that in 1900, only two doctors, Walter Reed and George Goethals, thought malaria was transmitted by mosquitos. The fact that malaria is a parasite spread by mosquitoes was proven prior to 1900 after decades of effort by many researchers. Walter Reed and George Goethals were not involved in proving that malaria was transmitted by mosquitos, according to a Johns Hopkins University historian.

Our fact-check sources:

• Ellen Amster, June 15, Email exchange with USA TODAY

• Randall Packard, June 16, Email exchange with USA TODAY

• National Library of Medicine, accessed June 16, A Brief History of Malaria

• Parasites & Vectors, Feb. 1, 2010, History of the discovery of the malaria parasites and their vectors

• Malaria Journal, July 9, 2013, Bad air, amulets and mosquitoes: 2,000 years of changing perspectives on malaria

• CDC, Sept. 23, 2015, Laveran and the Discovery of the Malaria Parasite

• CDC, Sept. 16, 2015, Ross and the Discovery that Mosquitoes Transmit Malaria Parasites

• Mayo Clinic, accessed June 13, Malaria

• The Nobel Prize, accessed June 13, Alphonse Laveran biographical

• The Indian Medical Gazette, 1899, Medical zoology: further researchers upon the cycle of human malaria in the body of the mosquito

• British Medical Journal, 1900, Experimental Proof of The Mosquito-Malaria Theory (republished in Yale Journal of Biology and Medicine 2002)

• Science, Feb. 26, 1915, Dr. A. F. A. King on Mosquitoes and Malaria

• British Medical Journal, July 1, 1899, Inaugural lecture on the possibility of extirpating malaria from certain localities by a new method

• Duke University, accessed June 14, Infectious Disease: Superbugs, Science & Society

• The Nobel Prize, Dec. 10, 1902, Ronald Ross banquet speech

• The Nobel Prize, Dec. 10, 1902, Award ceremony speech

• PBS News Hour, Sept. 13, 2017, How Walter Reed earned his status as a legend and hospital namesake

• Public Health United, Feb. 4, 2019, From Bad Air to Mosquito-Borne Disease: How folks found out malaria was transmitted by mosquitoes

• The British Medical Journal, Dec. 18, 1897, On some peculiar pigmented cells found in two mosquitos fed on malarial blood

• Encyclopaedia Britanica, Jan. 17, George Washington Goethals

• The British Medical Journal, Feb. 10, 1900, Remarks on the epidemiology and prophylaxis of malaria in the light of recent researches

• The British Medical Journal Oct. 6, 1900, Experimental proof of the malaria-mosquito theory

Thank you for supporting our journalism. You can subscribe to our print edition, ad-free app or electronic newspaper replica here.

Our fact-check work is supported in part by a grant from Facebook.

This article originally appeared on USA TODAY: Fact check: Many researchers blamed mosquitoes for malaria in 1900