America’s top bird flu expert says the virus outbreak in cows indicates the virus is one step closer to spreading to humans.
In an interview with STAT newsDr. Vivien Dugan — who also heads the CDC’s influenza division — emphasized that the risk to the general public is still “low.”
But she admitted that the repeated infections in cattle suggested the virus could become endemic to the species, raising the risk of H5N1 spillover to humans – who have close contact with the animals.
She also warned that officials were having trouble tracking infections because many farmers were not coming forward to get tested.
The map above shows states where bird flu infections in cattle have been reported
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Dr. Dugan warned: ‘These viruses change. If this were to be seeded into cows and a virus endemic to cows, this risk to humans would certainly increase.
‘And certainly, our pandemic planning (operation) has really thought about this and tried to be as vigilant as possible…
‘(The aim is) to try to understand not only the current risk, but also the future risk, so that we are as prepared as possible. But the risk can be quite high.’
She added, “That’s probably why I’m not sleeping that much right now.”
Dr. Dugan also warned that the CDC was struggling to track the virus and determine whether it had spread to people in other states.
After someone in Texas tested positive for the virus, it would be normal for the blood of their close contacts to be tested for antibodies to the virus — called serology tests — which would indicate whether the virus had spread.
But she said this could not be carried out as farmers closely involved in the case had refused to be tested.
A check mark indicates foods that tested positive for avian flu, while a cross indicates which foods tested for avian flu but were not found to contain the virus
It would also be a common practice for the CDC to monitor people on farms with infected livestock that showed symptoms of illness.
But she said that in many cases health officials had been “not that successful” in getting them tested.
The low number of people checked for the disease – 25 tested and 100 monitored so far – appears to underline these problems.
Dr. Vivien Dugan, who heads the CDC’s influenza division
By comparison, among poultry workers who have been dealing with H5N1 for more than two years, the CDC has monitored more than 8,000 people for symptoms.
She also said that in some cases the agency had difficulty accessing states because they had to be invited by local health departments, an invitation that did not always come.
“Six weeks ago we had a team pretty much ready to go when this really started to appear on our radar,” she added.
‘But this is not the average response situation for poultry workers. These are dairy farmers.
“Some states have been able to contact workers directly and conduct active surveillance. Others, of course, were not so successful.”
Scientists are concerned that bird flu will establish itself in a new species, as this suggests it has acquired mutations that allow it to infect and spread between new animals – and humans.
A total of 36 herds of cattle in nine states have tested positive for bird flu so far, sparking fears the virus could be spread through the air after tests discovered the pathogen in a cow’s lungs.
The virus has also been found in their milk and in supermarket milk, cottage cheese and sour cream – via possible transmission routes to humans.
But officials say these pose no risk because the virus “doesn’t live” in them. The products are treated with pasteurization, which involves rapid heating and cooling, to kill any microbes within them.
However, tests on ground beef, infant formula and milk powder have shown no trace of the virus.
U.S. officials have been repeatedly criticized for failing to publicly share data, including on whether pasteurized milk is still safe to drink.
Some scientists have said they will stop consuming milk until the FDA shares more data, though they have labeled the recent tests as “reassuring.”