(CNN) — A worker on a dairy farm in Texas tested positive for the avian flu, only the second case of a person in the United States who has contracted the H5N1 influenza strain. The US Centers for Disease Control and Prevention said that the person was diagnosed with the H5N1 virus and was recovering with mild symptoms.

The first case, in 2022, was diagnosed in a Colorado man who was directly exposed to poultry.

The risk to the public remains low, according to the CDC, but I still have questions. What exactly is the avian flu, and how is it transmitted? What symptoms do infected people experience, and what treatments exist? Is there a vaccine? Should people avoid eating poultry and drinking milk?

To guide us through these questions, I spoke with CNN wellness expert Dr. Leana Wen. Wen is an emergency physician and adjunct associate professor at George Washington University. She previously was Baltimore’s health commissioner.

CNN: What exactly is the bird flu?

Dr. Leana Wen: Bird flu, also called avian flu or avian influenza, refers to infections caused by the avian influenza Type A viruses. These viruses generally spread among wild birds, especially wild aquatic birds such as ducks and geese. They can also infect domestic poultry and other animals.

Avian influenza A viruses are divided into two categories: low pathogenicity avian influenza (LPAI) A viruses and high pathogenic avian influenza (HPAI) A viruses. Most LPAI viruses cause no signs of disease or mild disease in birds, but HPAI viruses can cause severe disease and are associated with high mortality. Some subtypes, for instance, have as high mortality rates as 90% to 100% in chickens. In addition, some LPAI viruses can mutate into HPAI variants.

CNN: How is bird flu transmitted?

Wen: By far, the most common form of transmission is from bird-to-bird. Infected birds can shed the virus through bodily fluids from their nose, mouth and feces. Other birds can become infected through direct contact with the virus particles, or through contact with surfaces contaminated with viruses from infected birds.

The H5N1 avian flu virus has been causing outbreaks among poultry in the US, with 48 states and over 85 million poultry now affected. This virus is highly contagious among domestic poultry and can spread through an entire flock within a matter of days.

CNN: Can bird flu be transmitted to other animals, including humans?

Wen: Yes, some forms of bird flu can be transmitted to other animals. Since 2022 in the US, the avian flu H5N1 virus has been detected in more than 200 mammals. In March 2024, a multistate outbreak of this virus was reported in dairy cattle. The person in Texas who was just diagnosed with it presumably contracted it through exposure.

In this case, the cattle are what is known as the intermediate host since the virus passed from birds to cattle and then to humans. It is also possible for humans to contract the virus directly from infected birds. Direct infection can occur if the virus gets into a person’s eyes, nose or mouth. It can also occur if the virus is inhaled or if a person touches a surface that has the virus on it and then touches their nose, mouth or eyes.

However, such transmission is rare and is primarily to be a risk for people who have close and prolonged contact with infected birds and their environments. The individual who was infected in Colorado in 2022, for instance, had direct exposure to birds and to culling poultry.

CNN: Can bird flu be transmitted from person to person?

Wen: There have been instances of people infected with bird flu transmitting it to other human beings, but this is rare and sporadic. Most such cases have involved family members with prolonged close household exposure to a symptomatic person. There have also been a few cases of human-to-human transmission in hospital settings after unprotected exposure.

With the current H5N1 spread among cattle and in poultry, “there is no sign of person-to-person spread of this virus at this time,” according to the CDC.

CNN: What symptoms do infected people experience?

Wen: Symptoms can range from mild, such as runny nose, sore throat, eye redness and headache, to severe disease-causing pneumonia and multi-organ failure. The person in Texas who was just diagnosed with H5N1 is reportedly only having conjunctivitis, or pink eye, as his only symptoms. The person in Colorado predominantly had fatigue.

CNN: What treatments exist?

Wen: There are a variety of antiviral drugs approved to treat influenza. These include forms that can be taken as pills by mouth. They reduce the likelihood of developing severe illness once someone is infected. Some antivirals are also approved for post-exposure prophylaxis, meaning that they are given to people who have not yet developed the illness but have had exposure to the virus.

CNN: Is there a vaccine against the bird flu? 

Wen: There are vaccines that target H5N1, but they are not yet produced in large quantities and are not currently commercially available. The seasonal flu vaccine does not protect people against infection from the avian flu. However, the seasonal flu vaccine does reduce the risk of becoming ill with human and bird flu viruses at the same time, and is recommended for everyone 6 months and above, especially those who have exposure to birds.

CNN: Is it safe to eat chicken and chicken eggs and to drink milk?

Wen: It is safe to drink milk that has been pasteurized. The process of pasteurization kills bacteria and viruses, including any influenza viruses that may be present in the milk. Similarly, it is safe to eat poultry, including chicken and eggs, that have been properly handled and cooked.

CNN: Can my pet bird get bird flu?

Wen: It’s possible, if your pet bird comes into contact with an infected animal. But if your bird is an indoor bird and has no contact with wild birds or other animals that are exposed to avian flu, your pet bird will not contract the virus.

CNN: Are there specific preventive measures that people should take?

Wen: The CDC has a list of measures that people can take. Most of them involve precautions to be undertaken by workers who are around poultry and people who have backyard bird flocks. They should use a few preventive steps, such as personal protective equipment when interacting with animals known to be or suspected to be infected with the avian flu.

In general, people should avoid direct contact with wild birds and observe them at a distance, not up close. They should also avoid contact with birds that look sick or have died. They should avoid touching surfaces where there are likely to be bird droppings. When traveling, they should stay away from bird markets and poultry farms and avoid eating raw or undercooked poultry products.

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