Five cases of the infectious children's bacterial disease known as HiB, or Haemophilus influenza type B, were reported in Minnesota in 2008, the most since a vaccine was introduced in the early 1990s, state health officials said Friday. Actually Minnesota hadn't had a Hib death since 1991. Now the state is facing its biggest outbreak since 1992, and it may not be just that one state, warns Anne Schuchat, MD, director of the CDC's National Center for Immunization and Respiratory Diseases.

Authorities are particularly concerned about bacterial meningitis caused by HiB (Haemophilus influenzae type B) in children. Meningitis is the inflammation of the tissue surrounding the brain and spinal cord, and can be caused by viral or bacterial infections.

Three of the five children, including a dead child, had not received any vaccine, due to a decision by their parents. But a shortage of Hib vaccine may also have contributed, CDC officials said. But the thing is that one in 20 children infected with Hib dies, according to the CDC. And survivors of the disease can become deaf; 10 to 30 percent have permanent brain damage.

However it is not the vaccine shortage that caused the infection of the five Minnesota children, federal and state health officials said. Three of the children had not received any vaccination because of their parents' decisions, not because of a vaccine shortage, officials said.

Dr. Anne Schuchat, head of immunization at the federal Centers for Disease Control and Prevention, said Friday that the increase in Minnesota cases in 2008 was "very unusual" and something the CDC has not seen elsewhere.