Influenza B is a type of flu that is similar to influenza A. However, while A usually afflicts people in the early winter, influenza B can infect any time of the year. Another difference between the two, according to Dr. Vincent Racaniello, a professor at Columbia University, and author of "The Virology Blog," is that type B can only pass from human to human unlike type A bird flu or swine flu. However, researchers have found that gray and harbor seals can contract influenza B as well.
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Type A and B share many symptoms.
One of the earliest symptoms of type B influenza is a fever. The National Institute of Health reports that the fever can come on quickly and go as high as 106 degrees. However, according to the Penn State College of Medicine, while A and B influenza share the same symptoms, type B generally produces much milder symptoms, so the fever will not be as acute. Also, the National Institutes of Health (NIH) reports that adults usually have a lower fever temperature than children do. The fever is often accompanied by body aches and fatigue.
Penn State Medical Center also reports that as the fever begins to leave, respiratory symptoms begin to develop. These symptoms are a stuffy or runny nose, cough and sore throat. These symptoms can become worse over time, and even turn into bronchitis or pneumonia if not treated. While these symptoms will usually disappear within a week, the cough can remain for several weeks.
There are times when type B influenza can affect the stomach also, which is why some people refer to it as the "stomach flu." The stomach flu is not a different type of flu virus; it is simply symptoms of the flu that affect the stomach. Some of these symptoms, as listed by the NIH, include vomiting, nausea and loss of appetite.
Influenza B symptoms, while the same as influenza A symptoms, are not quite as severe in their intensity. When you get a flu shot, it is meant to protect you from both influenza A and B strains.