The name malaria comes from the medieval Italian for bad air, and for centuries people blamed the smell of swamps such as Rome’s Pontine marshes for the disease called Roman fever. This episode traces malaria across more than 50,000 years, with a spike about 10,000 years ago as farming created mosquito habitat, and its arrival in the Americas with European settlers and the transatlantic slave trade. In 1880 the French army doctor Alphonse Laveran, working in Algeria, saw organisms inside red blood cells, the first protist identified as a cause of disease, and Ronald Ross and Carlos Finlay went on to connect the parasite to the mosquito.

Only the female Anopheles bites, for the protein to make eggs, and her saliva carries sporozoites that pass through Kupffer cells into the liver. They multiply silently for eight to 30 days, then escape wrapped in liver cell membrane and burst from red cells in synchronized waves that drive the fevers and chills. The episode cites 2024 figures of about 282 million cases and 610,000 deaths, around 95 percent in sub Saharan Africa. DDT brought resistance, and in 2023 the WHO endorsed the RTS,S and R21 vaccines.

• Nearly 10 percent of the Plasmodium genome is devoted to evading or subverting the immune system
• Plasmodium vivax hypnozoites can lie dormant in the liver for months or years before a relapse
• Plasmodium falciparum makes infected cells sticky so they avoid the spleen, which can lead to cerebral malaria
• Malaria is estimated to cost Africa about $12 billion a year
• Mosquitoes in some areas have begun biting earlier in the evening, before people get under bed nets