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An outbreak of infections linked to McDonald’s Quarter Pounders is causing concern among many people in the United States that they are being exposed to dangerous E. coli bacteria.

It is not yet known which specific food ingredient in the burgers is contaminated, but dozens of people in at least ten states have become ill with E. coli infections since Tuesday, including one death, according to the U.S. Centers for Disease Control and Prevention.

The type of bacteria involved in this outbreak is E. coli O157:H7.

“For this particular strain of E. coli that has been in the news – it’s called O157:H7 – the groups most at risk tend to be older adults and very young children,” said Dr. James Gaensbauer, a pediatric infectious disease physician at the Mayo Clinic Children’s Center in Rochester, Minnesota.

Although E. coli is very common and can cause a range of health problems, including urinary tract infections and stomach flu, “this particular strain causes primarily gastrointestinal symptoms such as abdominal cramps, vomiting and, most importantly, painful diarrhea that can sometimes turn bloody.” Dr . Marcus Pereira, assistant professor of clinical medicine at Columbia University College of Physicians, said in an email.

“Some people may also develop a fever and eventually become dehydrated because they don’t eat or drink much when they have diarrhea,” he said. “The good news is that most people with E. coli O157:H7 recover on their own, although it can sometimes be severe.”

McDonald’s customers are urged to seek medical attention if they have eaten a Quarter Pounder and develop symptoms of an E. coli infection.

What are the symptoms and how is it treated?

E. coli, or Escherichia coli, is a common type of bacteria that lives in the intestines of people and animals, but some E. coli can make people sick. People can become infected by ingesting E. coli through contaminated food or water, or through contact with animals, the environment or other people where the bacteria are present.

“Also, it occurs in clusters that may center around a particular exposure or risk, and that may happen perhaps every few years,” Gaensbauer said. “It’s relatively common and is something I probably treat a few times a year.”

According to the U.S. Food and Drug Administration, people infected with harmful E. coli may notice symptoms anywhere from a few days to nine days after exposure to the bacteria. A person can be tested for the presence of E. coli in their stool.

Symptoms of infection include diarrhea, particularly lasting more than three days, and fever over 102 degrees Fahrenheit. Some people may also experience severe stomach cramps and vomiting.

Most healthy people may not develop symptoms, Gaensbauer said.

But “most of the time the symptoms to look for are diarrhea,” he said. “The severe types of diarrhea caused by E. coli can often begin with loose stools, a watery type of diarrhea, but occasionally progress to bloody diarrhea.”

Most people recover without treatment in about a week, but some may develop serious health problems and require hospitalization.

“There is a particular type of E. coli known as Shiga toxin-producing E. coli (STEC) that has been implicated in serious outbreaks of foodborne illness. “Exposed people could experience bloody diarrhea and even kidney failure,” said Dr. Leana Wen, an emergency physician and professor of health policy and management at George Washington University’s Milken Institute School of Public Health, last year.

The CDC estimates that there are approximately 265,000 Shiga toxin-producing E. coli infections in the United States each year.

“Treatment consists of supportive care of symptoms and fluids for hydration,” Wen added.

Infection with STEC can lead to a serious health condition called hemolytic uremic syndrome, which can lead to kidney failure or even death. And O157:H7 is one of these types of bacteria.

“In the early stages of an E. coli infection with diarrhea, fluid intake is the most important treatment, so infected people should drink plenty of fluids if they can tolerate it. Children are at greatest risk of dehydration and products such as Pedialyte are often recommended in this situation,” Pereira wrote in the email.

“Sometimes patients require intravenous fluids in a medical facility if they are more severely dehydrated. For E. coli O157:H7, antibiotics are controversial and generally not recommended because there is evidence that they may actually increase the risk of hemolytic uremic syndrome,” he said.

For this reason, the CDC warns against the use of antibiotics for STEC infections.

“The other thing we’re really paying attention to with this thing is that sometimes there are medications that people take to slow down their bowel movements when they have diarrhea, and those medications are not recommended,” Gaensbauer said. “The idea is that you might not want to keep the bacteria and the toxin – maybe having diarrhea is better. Anyone who fears that they are suffering from an E. coli infection should definitely consult their doctor before taking diarrhea medication.”

The best way to prevent E. coli infections, according to the CDC, is to keep your hands clean through frequent washing, prepare food safely and drink clean water.

“Undercooking meat is a common and serious problem. “Infectious organisms may not be killed at lower temperatures,” Wen said. According to the U.S. Department of Agriculture, thoroughly cooking meat to an internal temperature of 160 degrees Fahrenheit kills E. coli O157:H7.

Another way to prevent illness is to wash vegetables and fruits thoroughly before eating them.

“Even if you want to peel them, you should wash them under running water first. It is neither necessary nor advisable to use soap, dish soap, disinfectants or other solutions,” Wen said.

“Be careful about which containers and utensils come into contact with raw meat. Do not put salads or cooked meats in these containers,” she said. “Also, don’t wash any other uncooked meat or raw seafood in your sink. This could spread bacteria and you could inadvertently contaminate other foods.”

The CDC also notes that choosing pasteurized milk and juices can reduce the risk of E. coli exposure because the pasteurization process kills harmful germs, including E. coli.