On June 1, the U.S. Centers for Disease Control and Prevention announced four more people have died from the most recent E. coli outbreak linked to romaine lettuce, bringing the death total up to five.

Those who died resided in nearly every corner of the country; Arkansas, California, Minnesota and New York. The lettuce was still available for sale two to three weeks ago, before it was taken off the market.

As of May 16, 197 people in 35 states were reported to have fallen ill to the outbreak, according to the last update by the CDC. Some of those affected said they had not specifically eaten romaine lettuce but had come into contact with those who did.

The effects of this specific outbreak have been so severe, nearly half of those who fell ill said they were admitted to hospitals. Six people in Canada were reported and confirmed to have fallen ill to the outbreak as well.

The outbreak is believed to have originated in Yuma, AZ where the lettuce was harvested. The U.S. Food and Drug Administration indicated the harvest season for romaine lettuce is now over but investigators are still trying to narrow down the exact location and reason for it.

Escherichia coli, abbreviated E. coli, is an infection that varies from person-to-person, according to the CDC website. Strains of E. coli are found in foods, the environment and the intestines of people and animals.

It is a large group of diverse bacteria but the pathogenic toxin known as Shiga (SHEC) is the one that is most often reported in food outbreaks. However, other types of E. coli have been reported in the news as well. In 2011, there was a large outbreak in Europe known as enterohemorrhagic E. coli (EHEC).

As with most illnesses, young children and elderly people are more likely to suffer severe effects of E. coli but it can cause serious illness in healthy individuals as well. Other kinds of E. coli can trigger a urinary tract infection (UTI), respiratory illnesses, and pneumonia.

Symptoms of E. coli typically manifest 3-4 days after ingestion. Those first couple of days are known as an “incubation period”, where the infection begins to launch its attack on the body. There are some cases where the incubation period has been shorter. Mild pain in the stomach and non-bloody diarrhea are typically signs that worsen over a couple of days.

In this most recent outbreak, 26 people were confirmed to have experienced hemolytic uremic syndrome (HUS). Typically only 5 to 10% of individuals develop HUS.