Bird flu wipes out 20 million chickens in the US, sending egg prices skyrocketing

Data from the U.S. Department of Agriculture (USDA) shows that the staggering losses also include hens culled to contain the virus. That, in turn, has contributed to record high egg prices across all types of production, including conventional, cage-free, and certified organic systems, the USDA said in a report released Jan. 10.

The federal government has spent $1.25 billion to compensate farmers for chickens lost to bird flu since the outbreak began, in an effort to encourage farmers to report infections and help stop the spread of the virus, CBS News said in a press release.

Why are there so many bird flu cases now? Bird flu cases spike in winter when migratory wild birds carry the virus south, where the cooler weather helps it spread.

This winter, the virus spread beyond poultry to dairy herds. Hundreds of infected herds were linked to contaminated raw MILK. California was hit particularly hard, prompting the state to declare a state of emergency.

Although the outbreak has devastated poultry populations, the Centers for Disease Control and Prevention (CDC) has reported only 66 cases of bird flu in humans in the U.S. since the virus emerged, with most infections being mild and occurring in farm workers who had close contact with infected animals.

However, one tragic fatality was recently reported in Louisiana associated with the D1.1 strain of the virus, which was spreading among wild birds.

Despite this, researchers believe that the strain responsible for many human infections has mutated and become less dangerous to humans than other strains circulating in the wild.

The U.S. Department of Agriculture has announced plans to stockpile a new poultry vaccine that targets the D1.1 strain of the virus. But officials say mass vaccination is unlikely due to concerns it could mask symptoms, which could disrupt international poultry exports .

The virus has already spread to people and pets through contaminated food. In two separate cases, raw pet food made from infected animals has been linked to the deaths of cats in California and Oregon.

"All recent detections of H5N1 [bird flu] in cats have had the following common features: infected cats ate wild birds, unpasteurized milk , raw poultry, and/or raw poultry pet food," a Food and Drug Administration spokesperson told CBS News.