(Bloomberg) -- A Michigan farmworker tested positive for bird flu, the first of three US human cases connected to an outbreak in cattle to show respiratory symptoms.  

The farmworker, who likely contracted the virus from an infected cow, reported a cough as well as irritated and watery eyes, the Centers for Disease Control and Prevention said Thursday. No other workers on the farm reported respiratory symptoms, the agency said. The worker was given an antiviral and has remained home.

The strain of highly pathogenic avian flu, known as H5N1, can jump between species and has sometimes caused lethal disease in people, raising concerns that it poses and pandemic threat. There are no indications of human-to-human spread, and the risk to humans remains low, the CDC said. 

Still, the US is ramping up surveillance, as the Department of Agriculture announced $824 million in new funding for monitoring cattle. More than 40 people have been tested for bird flu and more than 350 people have been monitored for symptoms, including 220 in Michigan. The CDC has not been invited to conduct surveillance in states, but the agency is “ready to go on the ground if need be,” Principal Deputy Director Nirav Shah said on a call with reporters. 

More Testing

The country’s first human case of bird flu from cattle was reported in a Texas farmworker in March, and a second case was found in a Michigan farmworker in May. Both had symptoms of an eye infection, received antiviral treatment and recovered. The third patient works at another Michigan farm.  

The Atlanta-based agency would like to test anyone on a farm who has been exposed to bird flu, Shah said, not just those with symptoms. The US has stockpiles of antivirals and vaccine candidates on hand should health officials determine the risk to humans has increased.

Some farmers have resisted testing of cows and workers because of conerns about lost milk production. That’s raised the stakes for the CDC to monitor wastewater for abnormal levels of influenza A, a broader virus category that includes H5N1. The agency said it has been in touch with Kansas, where prolonged high levels of influenza A have been observed in sewage at one site. 

Read More: Bird Flu Is More Widespread Among Dairy Cows, Sewage Tests Suggest

According to the CDC, 67 cattle herds in nine states have now tested positive for bird flu. Cows tend to recover from infection and none have yet died from infection, USDA Deputy Assistant Secretary Eric Deeble said on the call. 

The USDA also announced a voluntary pilot program to test cattle herds that aren’t known to be infected with bird flu. The testing will reduce the risk of the virus spreading and add to the government’s knowledge of the disease, Deeble said. 

Vaccine Talks

The US is in talks with Moderna Inc. and Pfizer Inc. about the development of messenger RNA bird flu vaccines for humans. The government is working out support for a late-stage trial of Moderna’s shot, the Financial Times reported, citing unidentified people close to the discussions. CSL Seqirus, a vaccine maker, said earlier Thursday that it was selected by the Biomedical Advanced Research and Development Authority to complete the finishing stages of production of a bird flu vaccine candidate. 

CSL will deliver about 4.8 million doses of a vaccine candidate that is well-matched to one of the components of H5N1 that’s now circulating, CSL said. The doses will be finished at the end of this summer, David Boucher, director of infectious disease preparedness at the Administration for Strategic Preparedness and Response, said on the call with reporters. For now, ASPR doesn’t recommend vaccination against H5 viruses and will decide on who receives priority for shots if they become necessary.

Given the levels of virus in raw, unpasteurized milk and the extent of spread in cows, the CDC said they expect more human and cattle cases to be identified. The USDA has offered incentives to farms to help prevent the spread of the virus, including personal protective equipment and reimbursements for veterinary expenses and the cost of shipping samples.

--With assistance from Ilena Peng and Madison Muller.

(Updates with comments from CDC call starting in first paragraph.)

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