WASHINGTON, Sept 12 (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 ( LH ), 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.