Another hypothesis is that this resurgence is an unusually virulent return to a natural cyclical pattern of the disease.
“This pattern was evident up until the 1940s and declined in the 1960s, in tandem with the widespread introduction of antibiotics,” the authors write.
While the recent upsurge in cases could represent a return to epidemic cycles, their analysis suggests “that the increase by seven times between 2011 and 2016, the lowest and highest points in the current cycle, is of greater magnitude than epidemic increases in previous years.”
It doesn’t help that a person can have scarlet fever for up to a week before symptoms really begin to show, making the spread of the illness more likely.
“Whilst current rates are nowhere near those seen in the early 1900s, the magnitude of the recent upsurge is greater than any documented in the last century,” said Lamagni who led The Lancet study.
The U.S. Centers for Disease Control (CDC) does not track cases of scarlet fever so it’s difficult to know if there have been spikes here, as well, but according to STAT News, “Scientists there are aware of the spike in cases in some jurisdictions, but a spokeswoman said officials have not heard of an increase in the United States.”
In lieu of answers, scientists merely have hypotheses. Another one, according to Vox, is that it’s not the bacteria that’s changed, but something in the immune systems of people that has changed or is being affected, which has caused them to be more susceptible to the Streptococcus pyogenes bacterium. Perhaps some environmental factor.
In an attached editorial along with The Lancet study, Professor Mark Walker from the University of Queensland in Australia wrote, “Group A Streptococci come in many different serotypes [variations]. Therefore, waning immunity against a particular serotype may open up the population to certain types of [strains] capable of causing scarlet fever.”
Another theory is that people coming down with scarlet fever now may be “co-infected” with another as of yet unidentified pathogen that predisposes them to the infection or weakens their immune system, allowing the strep to proliferate.
Most of the cases of scarlet fever were not severe, and there were no reported deaths in the UK (though there were a couple in Asia), but there was a higher than usual rate of hospital admission, and, the authors write, “the impact on public health has been substantial, particularly with regards to the management of the outbreak.”
In the meantime, the authors of the study say they are concerned about the spread of the illness, but not overly alarmed. The best defense to any pathogen is good hand washing practices. And if you or someone you know develops symptoms, get to a doctor sooner than later, and antibiotics will nip it in its scarlet bud.