A third close contact of a patient in Missouri who was hospitalized with H5N1 bird flu has reported that they also experienced symptoms, the US Centers for Disease Control and Prevention said Friday.

The Missouri case was detected through routine flu season surveillance, said the CDC, and is also the first time that an H5 strain has been picked up by the national surveillance system. The state hasn't had any reported cases of bird flu in cattle, but has seen signs of the disease in poultry and wild bird populations.

A close contact of someone with bird flu became ill on the same day, the C.D.C. reported. But the second person was not tested, and the cause of the illness is unknown.

A second health worker in contact with the Missouri patient who tested positive for bird flu also developed symptoms but wasn’t tested for influenza, the CDC said Friday.

The number of people who were in contact with the hospitalized bird flu patient in Missouri and developed symptoms is now up to three, officials said. All three have recovered. The other two symptomatic cases included a healthcare worker who tested negative for influenza and a household contact of the patient who developed symptoms at the same time as the hospitalized patient,

Health officials identified three contacts, including two healthcare workers, who were closely monitored after a bird flu patient in Missouri was recently hospitalized.