The changing seriousness of scarlet fever exemplifies the waxing and waning of the severity of infectious diseases. Scarlet fever was a mild illness when it was first recognised as a distinct disease during the second half of the 17th century. Samuel Pepys’ daughter may have been an early sufferer, but, as this extract from his diary of November 10th 1664 demonstrates, the disease was then difficult to distinguish from other common infections. “My little girl, Susan, is fallen sick of the measles, we fear, or at least, of a scarlett feavour.”Scarlet fever caused many deaths during the middle of the 18th century, before becoming mild again. By the middle of the 19th century it had returned as the leading cause of death in children; in 1856, Archibald Tait, who went on to become Archbishop of Canterbury, lost five of his six children to scarlet fever within a month. The disease caused at least 40,000 deaths in England in 1870, since when the death rate has steadily fallen, as shown in the following graph.
Scarlet fever is caused by the streptococcus bacterium, which also causes tonsillitis, pharyngitis (‘strep throat’) and, more rarely, rheumatic fever or kidney infections (glomerulonephritis). Scarlet fever is basically the same disease as a streptococcal throat infection, with the addition of a rash caused by a toxin (poison) produced by the bacterium. The steep decline in severity of the illness from the late 19th century remains unexplained. There has never been an immunisation for the disease, and effective antibiotics – primarily penicillin – were not available until the 1940s. The main reason for the decline in deaths due to scarlet fever, in common with measles, whooping cough and TB, is probably better nutrition. The final demise of scarlet fever may have been assisted by the introduction antibiotics, such as penicillin.