The Centers for Disease Control and Prevention (CDC) this week announced the salmonella outbreak that has been linked to backyard poultry — such as chicks and ducklings — has expanded, sickening a total of 279 people across 41 states.

The CDC shared the update on Thursday, the first since May 16. Since that time, an additional 227 people across 20 states have reported salmonella infections to the federal health agency. In total, 40 people have been hospitalized due to the illness, but no deaths have been reported to date.

AMID SALMONELLA OUTBREAK, CDC WARNS: DON'T 'KISS OR SNUGGLE' CHICKENS

Additionally, the CDC said, 70 of those who have fallen ill, roughly 30 percent, have been children under the age of 5.

“Epidemiologic and laboratory evidence indicates that contact with backyard poultry, such as chicks and ducklings, from multiple hatcheries, is the likely source of these outbreaks,” the CDC said in its update. “People reported obtaining chicks and ducklings from several sources, including agricultural stores, websites, and hatcheries.”

The federal agency also noted that one of the strains sickening people “has been identified in samples collected from backyard poultry in Ohio.”

Salmonella infections can cause diarrhea, vomiting, fever and abdominal cramps. Illnesses are more likely to be severe in the elderly and infants, according to the CDC, which estimates salmonella causes about 1.2 million illnesses in the U.S. per year.

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In May, when 52 people were affected by the outbreak, the CDC warned to not “kiss or snuggle” chickens. It also issued a list of precautions the public should take when handling the animals to avoid contracting the illness, such as always washing your hands after handling a backyard flock and not letting the birds inside the home, especially in areas where food is prepared.

The CDC also said at the time that children younger than 5 or adults over 65 should avoid handling “chicks, ducklings, or other poultry” altogether.

Fox News' Paulina Dedaj contributed to this report.