A third person in the US has tested positive for H5 bird flu in connection to an ongoing outbreak in dairy cattle, the Michigan Department of Health and Human Services said Thursday. This is the second human case reported in the state and the fourth ever in the US.
This time, in addition to some of the eye symptoms seen with previous H5N1 cases, the farmworker reported a cough and other respiratory symptoms that are more typical of human influenza infections, the health department said.
“This individual had respiratory symptoms, including a cough, congestion, sore throat and watery eyes,” Dr. Nirav Shah, the principal deputy director of the US Centers for Disease Control and Prevention, said at a briefing Thursday.
“What the respiratory symptoms tell us, more than anything, is that this virus, like many viruses, can present in more than one way, and for that reason, we should remain alert, not be alarmed,” he added.
Experts said that the addition of respiratory symptoms doesn’t necessarily indicate that the virus has become more dangerous or that it may transmit more easily from person to person. Instead, they say, the person probably developed lung symptoms because of the route of infection, perhaps by breathing in infectious aerosols in the milking parlor instead of rubbing their eyes with contaminated hands.
“With the first case in Michigan, eye symptoms occurred after a direct splash of infected milk to the eye. With this case, respiratory symptoms occurred after direct exposure to an infected cow,” Dr. Natasha Bagdasarian, chief medical executive for Michigan, said in a news release. “Neither individual was wearing full personal protective equipment (PPE). This tells us that direct exposure to infected livestock poses a risk to humans, and that PPE is an important toolin preventing spread among individuals who work on dairy and poultry farms. We have not seen signs of sustained human-to-human transmission, and the current health risk to the general public remains low.”
About 220 people are being monitored in Michigan because of potential exposure to the virus, Shah said.
Michigan, the state with the highest number of dairy herds reported to be infected, is also beginning to conduct blood testing to see how many workers may have antibodies to the H5N1 virus, which would reflect past infections or exposures.
The CDC agreed that the risk to the general public remains low. But this case highlights the elevated risk to those who work with infected animals.
The CDC has recommended that dairy workers wear personal protective equipment to reduce their risk. The US Department of Agriculture has offered financial support to farms with infected animals to provide workers with protection.
“Previously, we focused on the importance of eye protection, given the conjunctivitis in the first two cases, but this case also underscores the importance of barrier protection, things like masks and other forms of protection for dairy workers, particularly those who are working with affected cows,” Shah said.
Research is ongoing into how infections are transmitting between cows and from cows to people who work with them.
This is the third human infection known to be caused by this highly pathogenic form of avian influenza that’s currently infecting dairy cattle in the US. None of the three people had contact with each other, but all worked with cattle, suggesting that they are instances of cow-to-human transmission. The other two cases involved eye infections, or conjunctivitis. The most recent worker had some mild eye symptoms but was not diagnosed with conjunctivitis.
The person had direct contact with infected cattle and notified local health officials that they were feeling sick. Their symptoms are described as mild.
The patient has been given the antiviral medication oseltamivir, the same active ingredient as Tamiflu, and they are isolating at home. Their family members have not developed symptoms, but they have also been offered antiviral medication as a precaution. None of the other workers at the dairy farm has gotten sick, and they are being monitored, the CDC said.
“Given the high magnitude of interactions between people and dairy cows as well as with contaminated milking equipment, it is unsurprising that there are more human infections,” said Dr. Seema Lakdawala, an infectious disease specialist at Emory University who is studying how the virus is transmitting in dairy barns.
“Every time the virus is able to replicate in a person, there is the potential for the virus to adapt to humans and gain molecular features for replication in the respiratory tract and to spread person-to-person,” Lakdawala said.
Flu viruses are classified by two of the proteins that sit on their outer envelopes: H, or hemagglutinin, proteins and N, neuraminidase, proteins. CDC testing has confirmed that this third person carries a flu virus with an H5 protein, and the agency will do further sequencing to determine whether the N portion of the virus is N1, as is suspected. It expects to have those results in the next few days.
The CDC confirmed Wednesday night that the person had an H5 influenza infection and forwarded the results to the Michigan Department of Health and Human Services.
The US Department of Health and Human Services announced last week that it was moving forward with a plan to repackage 4.8 million doses of a vaccine against H5N1 that is stored in bulk form in the Strategic National Stockpile. The bulk supplies would be put into multidose vials so they could be distributed and administered more easily.
Officials said Thursday that before the vaccine would be given, it would need to go through certain regulatory steps. They also said there’s not currently a plan to offer or recommend the doses to any specific group of people.
The fill-and-finish process to repackage the vaccines will take at least a couple of months, officials said in the news briefing.
In the meantime, Michigan’s health department is advising people working on poultry or dairy farms to get a seasonal flu vaccine.
“It will not prevent infection with avian influenza viruses, but it can reduce the risk of coinfection with avian and flu viruses,” the department said.
