Backyard poultry flocks are sickening people with an antibiotic-resistant strain of bacteria, health officials warn.

The CDC says 34 people have been sickened and 13 hospitalized with a strain called Salmonella Saintpaul, which is resistant to most frontline antibiotics.

No deaths have been recorded in the outbreak to date. 

Of the 23 patients with information available, all reported contact with backyard poultry flocks.

The patients were in 13 states, mostly in the Midwest, and were sickened between February 26 and March 31. 

Salmonella infections trigger diarrhea and stomach cramps within six hours and six days of infection, and symptoms normally resolve within four to seven days.

But in those most at risk, including children under five and adults over 50, the bacteria can spread to the bloodstream and cause the potentially fatal complication sepsis. 

Doctors treat the infection with antibiotics, but, in cases where the bacteria are resistant, it severely limits options and raises risks of serious complications. 

In the outbreak, 40 percent of the patients are under five years old. They range in age from one year to 78 years old. 

Of the states reporting sicknesses, six infections were recorded in Michigan, while five were in Wisconsin and Ohio.

Three were reported in Indiana, Kentucky and Maine, two in West Virginia and Maryland, and one each in Florida, Illinois, Mississippi, New Hampshire and Tennessee.

Analysis of patients' infections revealed all were infected with a strain that is resistant to the antibiotic Fosfomycin, abroad-spectrum antibiotic often used to treat salmonella infections.

Eight patients' infections were also resistant to at least one other antibiotic typically used to treat salmonella. 

Overall, 14 patients reported owning backyard poultry flocks, while 13 said they had purchased or obtained the birds this year.  

It is not clear what birds patients had contact with before being sickened, but these can include chickens, ducks and geese.

It was also not clear how the cases were linked, but health officials are investigating whether there is a poultry supplier that has an outbreak of the bacteria. 

Health officials have urged people who have contact with poultry to wash their hands with soap and water immediately after touching the birds, their eggs or anything in the area where they live or roam.

People have also been urged not to kiss poultry, not to eat or drink around them and to ensure children are always supervised with birds and wash their hands properly afterwards.

Those who believe they were sickened in the outbreak have been urged to contact their health provider. 

Chickens and other poultry often carry salmonella in their intestines and do not show any symptoms.

They can spread the bacteria via their feces, contaminated feathers and eggs.

Humans may pick up the bacteria after holding backyard poultry or touching their eggs or living spaces. 

Health officials said: 'Backyard poultry, like chickens and ducks, can carry Salmonella germs even if they look healthy and clean. 

'These germs can easily spread to anything in the areas where the poultry live and roam.'