Highly Pathogenic Avian Influenza

Take-Home Messages

  • This is the first reported spread of Highly Pathogenic Avian Influenza (HPAI) in cows, we are still learning how the virus is transmitted and how this impacts the animal and public health.
  • Dairy farms are segregating cows showing signs of illness, limiting potential viral loads in raw milk.
  • If HPAI virus is present in raw milk it is expected to be inactivated by milk pasteurization as less heat intensive pasteurization practices used in other foods have been shown to effectively reduce HPAI viral loads.
  • Viral remnants (e.g., genetic material) from inactivated HPAI virus can still be detected using PCR in pasteurized milk; however, this presence does not represent a public health risk because only live, infectious virus can cause an illness.

HPAI Factsheet (PDF)

Download a PDF version of this webpage: HPAI Factsheet for the Dairy Industry and Consumers

Spanish Version

Download a Spanish Version of the HPAI Factsheet.

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More Information on HPAI

About HPAI Virus

  • HPAI virus needs a living host to survive and proliferate; it cannot grow outside of the host, only die-off.
  • HPAI virus belongs to a group of enveloped viruses that tend to be more sensitive to environmental conditions compared to non-enveloped viruses like Norovirus and Hepatitis A.
  • HPAI is a virus that primarily infects birds. Human infections are rare and are primarily associated with prolonged direct contact with infected animals.
  • Cow-to-cow transmission has been confirmed by the USDA and raw milk from infected cows likely has a role in transmission. Respiratory transmission is a less common but not unlikely route of cow-to-cow transmission.
  • There are no documented human cases of HPAI being contracted from properly cooked or pasteurized foods.

HPAI Risk in Milk and Dairy Products is Extremely Low Because:

  • Infected cows that develop symptoms are segregated from the rest of the herd and the milk collected from these cows is diverted and destroyed. The prevalence of pre- or asymptomatic infections in cows and viral shedding is still being studied.
  • Studies on pasteurization of egg products and cooking of meat and poultry products have shown that heating regimes that are less strict than milk pasteurization are effective at inactivating HPAI virus. Data specific to milk pasteurization is still limited, and while we expect that pasteurization can substantially reduce the viral loads in raw milk, we still don’t know the full level of reduction milk pasteurization is able to achieve.
  • Raw milk represents a public health risk; however, the risk of bacterial pathogens in raw milk is much greater compared to risk of HPAI.
  • Data specific to aging of raw milk cheese is very limited; based on environmental persistence studies it would be hard to predict if 60-day aging required for raw milk cheese would be sufficient to inactivate all HPAI virus during aging. Regardless of the HPAI risk, the risk of bacterial pathogens is higher in raw milk cheese compared to pasteurized milk cheese.
  • Virus remnants (e.g., genetic material) from inactivated HPAI virus can still be detected in pasteurized milk using PCR; however, this presence does not represent a public health risk because only live, infectious virus can cause an illness. Studies that found PCR positive samples of pasteurized milk and dairy products, did not find live infectious virus in any of the tested samples.

What Should Dairy Producers Do?

  • Dairy producers should implement enhanced biosecurity practices to limit any contact of dairy cows with live or dead birds that could potently be infected with HPAI.
  • Dairy producers should closely monitor the dairy cows for any potential clinical signs of infection that may include:
    • Decrease in milk production.
    • Decrease in feed consumption.
    • Mild respiratory signs.
    • Abnormal feces.
    • Fever.
  • Dairy producers should segregate any cows with potential clinical signs and destroy any raw milk collected from these cows.
  • Dairy producers should use appropriate personal protective equipment (PPE) during work when cows with potential clinical signs are identified at the farm.
  • Dairy producers should report any cows with potential infections and test them to confirm infection.
  • Dairy producers are obligated to test any cows prior to interstate movement.
  • Laboratories and state veterinarians are obligated to report any positive tests to USDA APHIS.

Additional Resources