nfluenza A virus is one of the most prevalent pathogens, causing respiratory illness. These virus outbreaks are usually associated with mild symptoms, such as fever, headache, sore throat, sneezing and nausea, accompanied by decreased activity and food intake. In general, influenza virus infection is able to induce bronchitis and pneumonia. Influenza virus evolves rapidly because of a high mutation rate and may escape acquired immunity. Although influenza virus itself can lead to severe pneumonia, mortality is most often caused by complications of the infection or by pre-existing conditions, such as asthma, chronic obstructive pulmonary disease, pulmonary fibrosis or cardiovascular disease. Viruses are well known to cause exacerbations of asthma
