text: (CNN)The latest outbreak of bird flu -- the worst in the U.S. since the 1980s -- is not a likely threat to humans, reports the Centers for Disease Control and Prevention. But as with any potential threat to human health, they are preparing for the worst just in case. The CDC and the United States Department of Agriculture held a press conference Wednesday to talk about preparations. "The risk to humans is low, our food supply is safe," said Dr. John Clifford, the USDA's Chief Veterinary Officer. "We know how to address disease when we find it." Since mid-December, 16 states have seen bird flu turn up in commercial poultry, backyard chickens, and in flocks of wild and captive wild birds, according to the CDC. That number will likely grow as birds with the disease fly from one state to the next. On Monday, health leaders in Iowa said more than 5 million hens would have to be euthanized after bird flu was detected at a commercial laying facility there. In the United States, some 3.5 million birds had already been euthanized to prevent the spread of the disease, according to the USDA. Iowa has about 60 million laying hens, according to the Iowa Egg Council and is the top egg producer in the country. California and Minnesota, two of the country's top 10 egg producing states have also seen cases. The news is bad for the birds, but not for humans. The CDC considers the likelihood of bird to human transmission of the virus "low" according to Dr. Alicia Fry, a medical officer with the CDC national Center for Immunization and Respiratory Disease, Influenza Division, Epidemiology and Prevention Branch. "That said, human infections have occurred" with another strain of the virus, found in Africa and in Asia, so the CDC cannot rule out the possibility of human infection, Fry said. "We are cautiously optimistic" that it won't spread to humans, but "we are prepared for the possibility," she added. They are studying the current virus and creating candidate vaccines which could be used if one were ever needed. The USDA is also working on a potential vaccine for the birds. These are typical routine public health preparedness measures. The CDC said it is also monitoring at least 100 people who have worked with sick birds. None of the workers have gotten sick themselves. Most of the people who have become infected with the other strains of the virus in Asia and Africa have had direct or prolonged contact with infected birds. The virus does not spread through people eating chickens or eggs. Birds that are sick die quickly, according to Clifford. Incubation period is three to five days generally. With turkeys, they go off their water and their feed when they are sick and become lethargic or have a condition called "torticollis" or "stargazing" he said, and they die shortly after that. Farmers also see a drop in egg production. Commercial growers have taken extra precautions to disinfect vehicle tires and any equipment that comes into contact with the birds. Workers must also disinfect their shoes and hands when they go from building to building to reduce contamination. With popular backyard birds, the USDA suggests people try and protect their animals from coming into contact with wild water fowl that may carry the virus. The CDC said, as with any evolving public health situation, they will continue to provide updated information as it becomes available. The good news is the virus doesn't like warm weather or strong sunlight, according to the USDA. So the cases should go down over the summer, but they are going to monitor the situation knowing that it could come back in the Fall.
target: The CDC says "the risk to humans is low," but, as always, they are preparing for the worst case .
  You can't get bird flu from eating poultry or eggs .
  At least 100 people who worked with the sick birds are being monitored for any sign of sickness .
  So far 3.5 million birds have been euthanized .