(CNN) The US Centers for Disease Control and Prevention reported 31 additional cases of E. coli illness Wednesday in the ongoing outbreak linked to romaine lettuce from the Yuma, Arizona, growing region.
This brings the total number of ill individuals to 84 people across 19 states. Colorado, Georgia and South Dakota join the growing list of states impacted since the first individuals started feeling unwell March 13.
Health officials investigating the outbreak have obtained information on 78 of the sick patients and found that 42 of them have been hospitalized. They do not have information on six further patients, and therefore it is not known whether they were hospitalized.
"This is a higher hospitalization rate than usual for E. coli O157:H7 infections, which is usually around 30%. Health officials are working to determine why this strain is causing a higher percentage of hospitalizations," the agency said in a statement Wednesday.
Brittany Behm, a spokeswoman with the CDC's Division of Foodborne, Waterborne, and Environmental Diseases, said that "health officials are doing additional lab testing of this strain to test how severe of illness it can cause. It's looking to be particularly nasty bug. Hopefully, more lab results will come in that can tell us more about the particular strain and if that's what is causing more hospitalizations."
Of those hospitalized, nine have developed hemolytic uremic syndrome, a type of kidney failure associated with an E. coli illness that can be life-threatening.
The individuals who most recently became ill began experiencing symptoms April 12. Those symptoms include severe stomach cramps, diarrhea and vomiting. They begin, on average, three to four days after ingesting the bacteria. Most people recover in five to seven days. Those most at risk for E. coli illness include the very young, the very old and individuals with compromised immune systems.
"If someone has bad diarrhea, especially if they have bloody stools, they should see their doctor. They could have E. coli O157, and doctors should consider this could be the cause," said Dr. Patricia Griffin, chief of the CDC's Enteric Diseases Epidemiology Branch. "We recommend this not be treated with antibiotics, because doing so could increase the chance" of hemolytic uremic syndrome. Getting plenty of fluids to prevent dehydration is the recommended treatment, Griffin said.
In the meantime, the agency repeated its advice to consumers: "Do not eat or buy romaine lettuce unless you can confirm it is not from the Yuma, Arizona growing region. Restaurants and retailers should not serve or sell any romaine lettuce from the Yuma, Arizona growing region."