A recent salmonella outbreak has infected over a hundred people in half of the United States, and health officials have not determined what is causing it.
On Friday, the Centers for Disease Control and Prevention issued a notice that it was investigating an outbreak of the strain Salmonella Oranienburg. On Sept. 2, the CDC identified 20 infections, but the outbreak has grown rapidly since then.
As of Sept. 15, the number of infected has reach 127 people, including 18 hospitalizations across 25 states. The outbreak began Aug. 3; the last reported case was on Sept. 1, with no deaths yet reported.
But officials believe the number of sick people is likely much higher since some people recover from illness without medical care and aren't tested for salmonella. Further, it can take up to four weeks to determine whether someone was part of an outbreak.
Still, officials aren't sure what's causing it.
"State and local public health officials are interviewing people about the foods they ate in the week before they got sick," the agency said in a statement. "CDC is analyzing the data and has not identified a specific food item as a potential source of this outbreak."
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According to CDC data, reported cases have stretched across the U.S. mainland, with Texas, 45, and Minnesota, 13, seeing the most reported cases. The infected have ranged from less than a year old to 82 years old, and 59% of sick people are females.
Despite not knowing the food source, health officials said they have identified people in multiple states who ate at the same restaurant and became ill. Investigating these "subclusters" may provide an definitive answer.
Symptoms of salmonella include diarrhea, vomiting, fever, stomach cramps and dehydration, which can begin six hours to six days after being exposed to the bacteria, according to the CDC. Most people recover without treatment after four to seven days.
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Since there is no definitive cause, the CDC recommends people practice food safety measures such as cleaning utensils, hands and foods, as well as separating different foods and making sure all food is cooking to a high enough temperature. The agency also recommends refrigerating perishable foods within two hours and thawing foods in a refrigerator.
Children under the age of 5, as well as people 65 years and older and those with weakened immune systems, may experience more severe illness from salmonella.
Contributing: Kelly Tyko, USA TODAY
Follow Jordan Mendoza on Twitter: @jordan_mendoza5.
This article originally appeared on USA TODAY: US salmonella outbreak found in Texas, Minnesota and 23 other states