Scarlet fever is a disease resulting from a group A streptococcus (group A strep) infection, also known as Streptococcus pyogenes.[1] The signs and symptoms include a sore throat, fever, headaches, swollen lymph nodes, and a characteristic rash.[1] The rash is red and feels like sandpaper and the tongue may be red and bumpy.[1] It most commonly affects children between five and 15 years of age.[1]

Scarlet fever affects a small number of people who have strep throat or streptococcal skin infections.[1] The bacteria are usually spread by people coughing or sneezing.[1] It can also be spread when a person touches an object that has the bacteria on it and then touches their mouth or nose.[1] The characteristic rash is due to the erythrogenic toxin, a substance produced by some types of the bacterium.[1][4] The diagnosis is typically confirmed by culturing the throat.[1]

As of 2020 there is no vaccine.[5] Prevention is by frequent handwashing, not sharing personal items, and staying away from other people when sick.[1] The disease is treatable with antibiotics, which prevent most complications.[1] Outcomes with scarlet fever are typically good if treated.[3] Long-term complications as a result of scarlet fever include kidney disease, rheumatic heart disease, and arthritis.[1] In the early 20th century, before antibiotics were available, it was a leading cause of death in children.[6][7] An antitoxin was produced before antibiotics; however, it was never made in sufficient quantities, and could not be used to treat any other disease as antibiotics can.

There have been signs of antibiotic resistance, and there have been recent outbreaks in Hong Kong in 2011 and in the UK in 2014, with occurrence rising 68% in the UK in the four years up to 2018. Research published in October 2020 has shown that infection of the bacterium by three viruses has led to stronger strains of the bacterium.[5]