Imagine your child comes to you complaining of a stomachache and sore throat. Most likely you would think it was just a common cold or, at worst, the flu.

But as the symptoms worsen, his body temperature skyrockets and he begins to vomit. At this point, you would probably rush to the doctor. Imagine your surprise when the doctor gives you the prognosis: your child has scarlet fever!

Most parents would feel a wave of fear and uncertainty rush over them. Scarlet fever? Wasn’t that eradicated in the early 1900s?

Yet this situation has been a reality for many thousands in Great Britain over the last few years.

Scarlet fever terrorized Victorian Great Britain in the 19th century, killing tens of thousands. Largely forgotten, this old disease has been sweeping across Europe today, baffling scientists as to why it has returned. There were just over 2,000 reported cases in Great Britain annually leading up to last year, but almost 18,000 cases in England and Wales in 2015.

Why has it returned?

Scarlet Fever History

While it is unclear exactly when scarlet fever was first recorded in medical history, the ancient physician Hippocrates noted it in approximately 400 BC when he described patients with sore throats and bright skin ulcers.

About 1,400 years later, in AD 1000, physicians vividly described a measles-like disease that was much more dangerous. The first likely description of the illness showed up in the 1553 book De tumoribus praeter naturam by Giovanni Filippo Ingrassia, a Sicilian physician, in which he referred to it as rossalia or rosania.

Before scarlet fever could be treated with antibiotics, the disease killed more than 20,000 people in 1840 in Europe alone. During the Industrial Revolution, it frequently swept through urban areas as people lived in close quarters and hygiene was less than desirable.

The disease, which usually strikes children under age 18, first manifests itself with a rash and/or red bumps on the chest and abdomen. A severe sore throat (often full-blown strep throat) then occurs. It can sometimes be so severe that open ulcers form in the throat. This is usually followed by intense fever, chills, loss of appetite, nausea and vomiting. According to eMedicineHealth, during the mid-1800s, death occurred in 15 to 20 percent of cases.

Two primary factors contributed to the end of the epidemic in pre-antibiotic Victorian England. First, the advent of milk pasteurization, which required heating it at high temperatures. This helped kill bacteria that was easily transferred in raw milk.

Second, a scarlet fever serum was developed from horses that also greatly reduced human mortality beginning in 1900.

Perhaps the greatest tool in the fight against it, however, came in the 1920s when British scientist Alexander Fleming accidentally discovered penicillin in his laboratory at St. Mary’s Hospital in London.

All of these discoveries slowly transitioned it from feared killer to an ailment that could be easily treated. Today, it is roughly equivalent to the flu virus in severity.

Europe’s State of Affairs

So why is this disease sweeping across nations in 2016? Schools, parents and family doctors have been warned about the disease as levels have reached a 50-year high. They have been told to beware of scarlet fever as the once-feared Victorian disease has made an alarming comeback.

According to Public Health England, outbreaks in the country have risen steeply—with 6,157 new cases since September 2015. The figures also show that 17,586 cases occurred in England and Wales in 2015. This is the highest total since 1967.

For now, health officials in Great Britain are unclear as to why it has returned. Yet the sharp rise may reflect the long-term natural cycles in disease frequency seen in many types of infection.

According to Dr. Theresa Lamagni, head of streptococcal infection surveillance for Public Health England: “Symptoms usually clear up after a week and the majority of cases will resolve without complication as long as the recommended course of antibiotics is completed. Potential complications include ear infection, throat abscess and pneumonia. Patients who do not show signs of improvement within a few days of starting treatment should seek urgent medical advice.”

Resurging Diseases

Scarlet fever is not the only disease making a comeback. According to numbers compiled by the Centers for Disease Control and Prevention (CDC), from January to mid-April 2014, 129 cases of measles were reported in the United States. This is noteworthy because usually only about 60 are reported each year!

Consider also that 10 years ago, a significant multistate outbreak of the mumps occurred, with 6,584 reported cases in the U.S. Usually, only about 20 cases are reported annually.

A 2012 study published in the Journal of Pediatrics reported California’s worst whooping-cough outbreak in memory, with more than 9,000 people reporting cases in 2010 in the state alone. This is thought to be spurred by a lessening of the effectiveness of old vaccines, according to Time magazine.

California was hit with the malady again in 2014. According to the California Department of Public Health, the outbreak hit “epidemic proportions” when 3,458 new cases were reported between January 1 and June 10—well ahead of the numbers during the same period of the 2010 outbreak.

Shockingly, bubonic plague made a comeback around the world as well with cases being reported in Africa, Asia and South America. Health magazine reported that “there have been 16 reported cases of plague, with four deaths, in the United States this past year. Most recently, a 16-year-old girl from Oregon was sickened and hospitalized after apparently being bitten by a flea on a hunting trip.”

During the 1800s, tuberculosis killed one out of every seven Americans and Europeans that were infected by it! According to Health, “It was believed that tuberculosis could be eliminated from the world by 2025, according to the National Institute of Allergy and Infectious Diseases. But it persists, killing between 2 and 3 million people globally each year. Though most Americans don’t consider TB a threat, it’s showing signs of a resurgence: there were 9,421 reported US cases of TB in 2014, according to the CDC, and 555 deaths in 2013 (the last year for which data are available).”

Although man’s knowledge of science and medicine hurtles forward at an unprecedented pace, we are a long way from solving some of the oldest diseases known to man.