Salmonella outbreaks linked to backyard poultry have sickened 163 people in 43 states, the U.S. Centers for Disease Control and Prevention said Thursday.

As of May 20, 34 people had been hospitalized, but no deaths had been reported. One-third of the confirmed cases involved children younger than 5 years. The actual number of people who have become ill is likely much higher than the reported number because many people recover from Salmonella infection without medical care and are not tested for it, the CDC said.

Even backyard poultry that appear healthy and clean can carry Salmonella bacteria, which can easily spread where the birds live and roam. The CDC offered safety tips for people with backyard poultry: always wash hands for 20 seconds after touching the flock or flock supplies; keep flock and flock supplies outside the house; do not let children younger than 5 years touch the birds (including chicks and ducklings) or anything in the area where the birds live and roam; and do not kiss or snuggle the birds.

When infected with Salmonella, most people develop diarrhea, fever, and stomach cramps anywhere from six hours to six days after being exposed to the bacteria, the CDC said. The illness usually lasts four to seven days, and most people recover without treatment. In some people, the illness may be so severe that the patient is hospitalized. Children younger than 5 years, adults 65 years and older, and people with weakened immune systems are more likely to have severe illness, the agency said.