California officials have declared a state of emergency as bird flu spreads, with infections rising in dairy cows and causing sporadic illness in humans in the U.S.
This raises new questions about the virus, which has been spreading for years in wild birds, commercial poultry and many species of mammals.
The virus, also known as type A H5N1, was first detected in U.S. dairy cattle in March. Since then, bird flu has been confirmed in at least 866 flocks in 16 states.
According to the US Centers for Disease Control and Prevention (CDC), more than 60 people in eight states have been infected, most with mild illnesses. U.S. health officials this week said one person in Louisiana had been hospitalized with the first known severe illness from the virus.
Here's what you need to know.
Why did California declare a state of emergency?
Gov. Gavin Newsom said he declared a state of emergency to ensure state staff and supplies were better prepared to respond to the outbreak.
California looked for bird flu in large milk tanks during processing. They detected the virus in at least 650 herds, representing about three-quarters of all affected U.S. dairy herds.
Dr. Maria Van Kerkhove, the World Health Organization's director of epidemic and pandemic preparedness, is calling for increased global surveillance of animal populations known to be susceptible to H5N1, including wild birds, poultry, pigs and cattle.
The virus was recently detected on dairy farms in Southern California after being present in the state's Central Valley since August.
“This proclamation is a targeted action to provide government agencies with the resources and flexibility they need to rapidly respond to the epidemic,” Newsom said in a statement.
What is the risk to the general public?
CDC officials emphasized again this week that the virus poses a low risk to the general public.
Importantly, there are no reports of the virus spreading from person to person, nor are there any signs that the virus has changed and is spreading more easily among people.
Overall, flu experts agreed with that assessment, saying it was too early to tell what course the epidemic might take.
“The completely unsatisfactory answer is: I don't think we know yet,” said Richard Webby, a flu expert at St. Jude Children's Research Hospital in Michigan.
However, virus experts are cautious because flu viruses are constantly mutating and small genetic changes can change the outlook.
Are cases becoming more serious?
This week, health officials confirmed the first known case of severe disease in the U.S. All previous cases in the U.S. – about 60 of them – were generally mild.
The Louisiana patient, who is over 65 years old and has health problems, is in critical condition. Few details have been released, but officials say a person developed severe respiratory symptoms after being exposed to a flock of sick backyard birds.
This makes it the first confirmed infection in the U.S. linked to backyard birds, the CDC says.
Studies have shown that the strain that caused a person's illness is found in wild birds but not in cattle. Last month, health officials in Canada said a British Columbia teenager was hospitalized with a severe case of bird flu, also caused by a strain of the virus found in wild birds.
Previous infections in the U.S. have almost exclusively involved farm workers with direct contact with infected dairy cattle or poultry. In two cases – an adult in Missouri and a child in California – health officials have not determined how they became infected.
Dr. Amesh Adaljia, a senior research fellow at the Johns Hopkins Center for Health Security and an infectious disease physician in Baltimore, said the H5N1 virus currently poses no threat to the general public, but that doesn't mean it should be completely ignored given the exposure of farm workers .
“We've really only had one serious case in the United States, and understanding why most cases are mild is also a big challenge,” Adaljia told CBC News.
The case in B.C. involved a strain more closely related to what's circulating in geese, while the Louisiana version was more closely related to what's circulating in poultry, Adaljia said.
How can people protect themselves?
The CDC and other experts say people who come into contact with dairy cows, commercial poultry or backyard birds are at increased risk and should use precautions, including respiratory and eye protection and gloves.
“If birds start to look sick or are dying, they should be very careful in handling the animals,” said Michael Osterholm, a public health expert at the University of Minnesota.
Day 67:19Why an infectious disease expert says we should pay special attention to H5N1
Dr. Samira Mubareka, an infectious disease physician and microbiologist at the Sunnybrook Research Institute in Toronto, says the case of a British Columbia teenager who became critically ill with the H5N1 virus shows it's time to pay more attention to the spread of bird flu and its changes as it spreads. spreads from birds to mammals.
The CDC paid for flu vaccines to protect farm workers against seasonal flu and the risk that workers could become infected with two types of flu at the same time, which could cause the bird flu virus to mutate and become more dangerous. The U.S. government also said farm workers who have close contact with infected animals should be tested and offered antiviral medications, even if they show no symptoms.
Canada has approved influenza A(H5N1) vaccines, but they do exist is not widely available vaccines for public use.
Dr. Jesse Papenburg, a pediatric infectious disease specialist at Montreal Children's Hospital, said Canadians should be aware of the increased risk of exposure and transmission of the virus to humans through contact with poultry and wild waterfowl, other animals or their environment.
“Be very situational aware of flu-like illnesses, especially as Canada and the United States enter the flu season,” Adalja said.
How else does bird flu spread?
In addition to direct contact with farm animals and wild birds, the H5N1 virus can be transmitted in raw milk. According to the U.S. Food and Drug Administration, pasteurized milk is safe to drink because heat treatment kills the virus.
However, high levels of the virus were detected in unpasteurized milk. And two brands raw milk sold in California stores were recalled in recent weeks after the virus was detected on farms and in products.
In Los Angeles, county officials reported that two domestic cats fed with recalled raw milk died of bird flu infections. Officials were investigating additional reports regarding sick cats.
The U.S. Department of Agriculture has stepped up testing of raw milk across the country to help detect and contain the outbreak. A federal order issued this month requires testing, which began this week in 13 states.
Canadian and U.S. health officials are urging people to avoid drinking raw milk, which can carry many germs in addition to bird flu.
The Canadian Food Inspection Agency as of December 6, it had examined over 900 samples of raw milk arriving at processing plants in all voivodeships. All samples tested negative.
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