Bird flu is a common name for avian influenza. Avian influenza has been around since the 1800’s and there have been sporadic outbreaks since then. The scientific name of the virus is AH5N1, but there are multiple subtypes of avian influenza virus and the virus continues to evolve over time. There have always been human cases, and some deaths but only related to contact with birds. The current avian influenza virus subtypes are extremely infectious to wild birds and poultry with a 60 to 100% mortality rate. Wild waterfowl, such as ducks and geese can spread the virus but usually do not get sick from it.

Infection in Cattle

In the last year avian influenza virus has mutated so that it has infected dairy cattle. Now there are several human cases in people who work with dairy cattle. Only about 10% of cattle with the virus have symptoms, but lactating cows are especially susceptible. There is evidence that cows can transmit the virus to other cattle. The virus has been found in raw milk, but not pasteurized milk. Drinking raw milk always has some risk of disease, but now that risk is much higher. There have been no human cases so far from drinking milk.

Infection in Other Mammals

Domestic cats are the most common other mammal that has been infected with A5HN1, but it has also been found in mink, foxes, raccoons, dogs, harbor seals, and most recently a dead polar bear. There have been no reported cases of human infection from contact with infected cats or dogs.

Potential for Human to Human Transmission

The AH5N1 virus has shown its potential to evolve rapidly, and this can happen in one animal. The influenza virus that caused the 1918 pandemic was an H1N1 virus that probably was initially a bird virus that mutated to infect humans. The current A5HN1 virus has shown no human to human transmission so far. The CDC currently rates the current public health risk of A5HN1 as low, but they are watching it carefully.

Human Symptoms of Avian Influenza

Most human cases have been mild, but severe illness and even death can occur.

Mild symptoms

• eye redness and irritation (conjunctivitis)
• mild fever (temperature of 100ºF [37.8ºC] or greater) or feeling feverish*,
• cough
• sore throat
• runny or stuff nose
• muscle or body aches
• headaches
• fatigue

Severe symptoms

• high fever or other symptoms listed above that limit or prevent usual activity
• shortness of breath or difficulty breathing
• altered consciousness
• seizures

Complications

• pneumonia,
• respiratory failure,
• acute respiratory distress syndrome,
• acute kidney injury
• multi-organ failure (respiratory and kidney failure),
• sepsis, septic shock
• and inflammation of the brain (meningoencephalitis)

What you can do now to limit your risk

• Do not touch or even get near dead birds
• Do not drink raw milk
• Keep cats inside and do not feed them raw milk or raw food
• Stay away from any wild animals (raccoons, foxes) that appear ill
• Keep up with current CDC bird flu recommendations at this website: Avian Influenza

Bottom Line

Avian influenza virus is able to mutate rapidly. In the last year it has become transmissible in dairy cattle. All human cases so far have been caused by contact with dead wild birds, poultry or dairy cattle. There has as yet been no human to human infection documented. The CDC reports that public health risk is currently low, but they are tracking animal and human cases carefully.