As the number of people infected with bird flu rises in the US, continued limits on testing may pose a problem as these cases crop up. Commercial labs are now developing tests that will be available by prescription, but the tests will still be recommended only for people in close contact with animals and animal products – even as cases in Missouri remain a mystery and wild bird migration and extreme heat may increase spillover opportunities, officials say. Blood tests have revealed a second person in Missouri exposed to bird flu with no known animal contact, officials with the US Centers for Disease Control and Prevention (CDC) told reporters on Thursday. This person lives in the same household as the patient who tested positive for H5N1 a few weeks ago, and both people developed symptoms at the same time. The second infection was discovered after the first patient tested positive and officials began serology testing for symptomatic contacts only. Five healthcare workers who developed symptoms after caring for the first patient were negative for H5N1 on blood tests, and a sixth healthcare worker tested negative by a PCR test after developing symptoms, officials said. That means the two positive Missourians didn’t seem to spread the virus to healthcare workers. But it’s not clear how either of them got sick in the first place. As the two positive people developed symptoms at the same time, health officials believe they were likely exposed to a source at the same time – though it is possible for patients to develop symptoms at different times in the course of illness, especially since one patient has significant health issues. Notably, the original source of their infection still hasn’t been identified. The patients may have had contact with animals or animal products that wasn’t detected on extensive health questionnaires, officials said. Quest Diagnostics announced on Wednesday that its test for H5N1 will soon be available with a prescription from a medical provider, and other commercial labs are also developing tests for the public. But the tests will only be recommended for people with close contact to animals or animal products like raw meat or milk. In “the lion’s share of situations”, most people with flu symptoms do not need an H5N1 specific test, said Nirav Shah, principal deputy director at the CDC. “It’s really when there’s an epidemiological exposure history that is suggestive of H5, where the H5 test would be warranted.” Neither of the Missouri cases would’ve been detected with limitations like these. However, the CDC still recommends that states regularly check positive flu A tests for H5N1, which is how the first Missouri case was found. The first human cases of H5N1 have also been identified in Washington among workers who were killing H5-infected poultry. The state now has two confirmed and five more presumed bird flu cases in humans. It’s not clear why so many people were infected, or whether antiviral medications were provided to the workers before they had contact with the sick birds. These drugs are one of the most effective ways to prevent infections from happening, yet they don’t seem to be rolled out widely for workers in very close contact with H5N1-positive animals. “Uptake of Tamiflu has been strong, but there’s still more work that we can be doing,” Shah said. He highlighted the importance of using personal protective equipment, like respirators and goggles, and making changes to how sick birds are culled. “Many of these outbreaks are occurring in places where there are cramped conditions, with poor ventilation, with a lot of birds, feathers, dust flying around,” Shah said. “Improving those can confidently reduce the risk to workers.” That’s a particular concern because the Washington outbreak may have been spread by migratory birds, he said. It’s now the fall migration season, and officials are concerned about new cases popping up among poultry – and the workers in close contact with them – in particular. So far in the US, there have been 31 confirmed human cases of bird flu, as well as the five presumptive cases in Washington and the newly confirmed case in Missouri, which will not be included in official counts because that exposure was only verified on one type of blood test. None of the new human cases in Missouri, Washington or California have been severe or required hospitalization, officials said. Almost half – 15 – of the human cases have been detected in California at 13 different dairy farms. Crystal Heath, a veterinarian, took photos and videos of dead cows with Xs across their udders on a massive farm with H5N1 cases in California’s Central valley. The cows were lying on the ground, near the road, Heath said, raising concerns about biosecurity and the treatment of potentially sick animals. Eric Deeble, deputy undersecretary for marketing and regulatory programs at the US Department of Agriculture, said an investigation is ongoing into the mortality rates of H5-infected cows in California, and he said there could be several factors at play, including excessive heat, management practices, and the density and proximity of the animals.