Influenza virus B is a genus in the virus family Orthomyxoviridae. Influenza B viruses are only known to infect humans and seals, giving them influenza. This limited host and range is apparently responsible for the lack of Influenza virus B-caused influenza pandemics in contrast with those caused by the morphologically similar Influenza virus A as both mutate by both antigenic drift and reassortment. Common body symptoms including fever, fatigue and body aches. In most cases respiratory symptoms, including cough, runny nose and sore throat will disappear within one week. Many Many strains of influenza B will cause irritation in the stomach, which include nausea, loss of appetite or vomiting.