Origin of human bird flu case in Missouri still unknown, U.S. CDC says

By Leah Douglas and Julie Steenhuysen

WASHINGTON (Reuters) - Epidemiologists have not yet identified exactly how a person in Missouri contracted bird flu last week, said the U.S. Centers for Disease Control and Prevention on Thursday.

The human case was the 14th diagnosed in the U.S. this year. The other 13 cases were among farm workers and linked to bird flu outbreaks on poultry or dairy farms.

The infected individual was admitted to the hospital with symptoms including chest pain, nausea, vomiting and diarrhea, said CDC principal deputy director Nirav Shah on a Thursday call with reporters.

It was unclear whether the patient's underlying conditions caused the symptoms or the flu.

The investigation into the origin of the infection is ongoing and the CDC has been unable to determine if the case was related to the current outbreak of bird flu in dairy cattle, Shah said.

"Right now, evidence points to this being a one-off case," said Shah.

Missouri has not invited the CDC to conduct an on-site investigation but the CDC is working closely with state health officials on its response to the case, Shah said.

Shah also said the CDC will work with five commercial laboratory companies - Aegis, ARUP, Gingko BioWorks, Labcorp, and Quest - to develop their own diagnostic tests for public health outbreaks, including bird flu.

The USDA said eight dairy herds had been infected with bird flu in California since the first cattle case was identified there on Aug. 30. Bird flu has infected more than 200 dairy herds in 14 states since March, USDA data showed.

The California herds are quarantined and the state is expected to conduct bulk milk testing at dairies within a geographic zone around the affected farms, said Eric Deeble, deputy under secretary for marketing and regulatory programs at USDA.

The agency does not know how the virus arrived in California, Deeble said.

The CDC will launch its program to vaccinate farm workers against the seasonal flu in October, Shah said. The campaign is meant to prevent dual infection with bird flu and seasonal flu, which could lead to virus mutations.

(Reporting by Reporting by Leah Douglas in Washington and Julie Steenhuysen in Chigaco; Additional reporting by Ahmed Aboulenein; Editing by Richard Chang)