Scarlet fever reached its highest level in England for 50 years, with more than 17,000 cases reported in 2016 – research in The Lancet shows.  The disease has been on the rise since 2014, but experts have not yet found a reason for the recent increase.
Doctors urge the public to know the symptoms, which include a pink rash, and seek help from their GP.
The 2017 data suggest that the rate may be declining, but experts remain cautious, saying it is "too early to know".
The bacterial disease, although highly contagious, is not usually serious and can be treated with antibiotics.
It is more common among children under 10.
A joint investigation by public health authorities in England and Wales found that the incidence of scarlet fever tripled by 2013 and 2014, increasing by 4,700 cases to 15,637 cases.
In 2016, there were 19,206 reported cases, the highest level since 1967.
Most of the outbreaks occurred in England.
"We're worried, it's a pretty dramatic increase," said Dr. Theresa Lamagni, chief of streptococcal surveillance at Public Health England, who led the study.
"We have always seen cases of scarlet fever, it's just that the scale in the past has been much lower than in recent years."
& # 39; Like sandpaper & # 39;
Scarlet fever is caused by bacteria known as group A streptococcus, and is spread by close contact with people who carry the organism, often in the throat, or by contact with objects and surfaces contaminated with the bacteria.
Symptoms include sore throat, headache and fever, accompanied by a red rash that is rough to the touch (sometimes described as "sandpaper").
Scarlet fever was a common cause of death in the Victorian era, but had declined greatly since the introduction of antibiotics.
However, immediate treatment remains essential to prevent the spread of the disease and the risk of additional complications such as pneumonia and liver damage.
It is recommended that anyone diagnosed with scarlet fever stay in their home for up to 24 hours after the start of treatment. to avoid transmitting the infection.
There is no vaccine against the disease and all cases must be reported by doctors to the local health authority.
Dr. Lamagni described the large number of cases of scarlet fever as "puzzling", adding that no identified underlying causes had been found.
Molecular genetic testing has ruled out a new strain of infection, and there is no suggestion that the disease has become resistant to the penicillin normally used to treat it.
He emphasized that the cases of the disease are "It is not more serious than before, it is only a matter of scale".
Several countries in East Asia have also reported an escalation in the last five years, including Vietnam, China, South Korea, and Hong Kong, but it seems that "there is no clear connection" between them and England.
Typically, cyclic natural patterns of scarlet fever occur every four or six years; the fall in 2017 suggests that the cycle may have peake d in 2016.
Dr. Lamagni said that the "slight decrease" in the number of cases in England this year might suggest that we have "turned the corner" but said that the number of cases "remained high".
In 2016, 620 outbreaks of the disease were reported, mostly in schools and day care centers.
Approximately one in every 40 cases is admitted to the hospital, although a little more than half are discharged on the same day.
"We encourage parents to be aware of the symptoms of scarlet fever and to contact their family doctor if they think their child might have it," said Dr. Lamagni.