The CDC issued a press release on November 25 warning of an increase in bacterial pneumonia infections in flu sufferers. While the two types of infection share some similarities, pneumonia is much more serious and has a higher mortality associated with it.

Streptococcal pneumonia occurs when the bacteria work their way into the lungs and multiply there. In weakened patients... the bacteria can also invade the blood and other bodily sites.

When the flu weakens individuals, they become more susceptible to additional infections from other disease organisms. This re−infection is often called a secondary infection. While secondary infections always rise during a flu epidemic, they generally occur among those 65 or older. The secondary infections being seen now are primarily of younger adults not normally prone to them.

These infections are being caused by strains of the bacterium Streptococcus. Streptococcal pneumonia occurs when the bacteria work their way into the lungs and multiply there. In weakened patients, such as flu sufferers, the bacteria can also invade the blood and other bodily sites.

In Denver, 58 cases of serious streptococcal infections were recorded in October; 20 is the norm. They were nearly all found in people under the age of 60.

Dr. Anne Schuchat of the CDC suspects that a similar increase is occurring nationwide, but has not been noticed because overall surveillance has not been nearly as intensive as it was in Denver.

Unlike the flu, streptococcal infections can be treated with antibiotics. Their severity means that patients and doctors need to keep an eye out for them, so they can be treated quickly. "Having a high fever and cough and then feeling miserable and then feeling better and then suddenly taking a turn for the worse—that is a serious warning sign," Schuchat said.

There is a vaccine called Pneumovax, which protects adults against 23 types of streptococcal bacteria. It is recommended for adults with diabetes, cancer, asthma and other conditions, as well as smokers. But only about a quarter of all adults who should get it do so, Schuchat said. Another vaccine, Prevnar, protects children against seven streptococcal strains.