Researchers trying to determine how a child in California could have contracted the H5N1 bird flu continue to learn more details about the case. But much about the situation remains unclear – and it is not certain that a definitive answer will be reached, an official involved in the investigation told STAT.
The incident involves a toddler who was taken to the emergency department of a hospital in Marin County, just north of San Francisco, earlier this month. The child had a high fever and was vomiting. A parent told a doctor at the hospital that the child had been drinking raw milk from a company called Raw Milk LLC. The company’s products were recently quarantined because some of them found on local store shelves, as well as the farm’s milk, tested positive for H5N1.
If this child, who has not yet been identified, is confirmed to have been infected with H5N1 through milk consumption, it will be the first such case recorded in the United States. But Lisa Santora, public health officer for Marin County, acknowledged to STAT that there is a decent chance the infection will not be confirmed.
Santora said a specimen was sent to the Centers for Disease Control and Prevention in the hope that their labs could do something that neither the local Marin County lab nor the state public health lab could do: confirm a flu infection and specify which type flu. flu – seasonal or bird flu – was the cause.
“It’s possible they can extract [enough viral material] and we can determine whether this is seasonal flu or bird flu. It is also possible that they cannot determine the order,” Santora said.
The province announced on its website last Friday that it was investigating a possible case of H5N1 in a child. Santora said it appears the family members did not know the milk they purchased was raw milk. Public health officials have warned consumers to avoid raw milk, which has not been pasteurized, amid concerns that it could transmit the H5N1 bird flu. Studies have shown that commercial pasteurization processes kill the virus in milk.
An initial test, which involved swirling a cotton swab around the child’s nostrils, was negative for influenza. But because of the known exposure to raw milk, a second flu test was performed the next day, during which the child’s mouth and throat were swabbed. That test was positive for influenza A, a category of flu viruses that includes the seasonal flu viruses H1N1 and H3N2, but also the bird flu H5N1.
But there was little virus in the swab, and when local and state public health laboratories tried to confirm the diagnosis and sub-type the virus — that is, to determine which influenza A virus was present — they could not do so. “So we only have a positive influenza A test and a symptomatic child,” Santora said.
Family members were tested for the flu, but all were negative, she said, adding that she thought if the child had had the seasonal flu, there might have been other infections in the household.
Milk from infected cows contains extremely high levels of H5N1. Cats on farms infected cows have died from drinking raw milk, and laboratory mice fed infected raw milk became so ill that they had to be euthanized. But it is not known whether consuming the virus in raw milk would pose the same risk to humans.
“We’re in that learning space ourselves,” Santora admitted. “There is biological plausibility that there could be a link between raw milk consumption [H5N1 infection].”
The child, who had no classic symptoms of flu infection, has since recovered.
Last month, another child in California, in Alameda County, tested positive for H5N1. In that case, it has not been established how the child became infected with the virus.