Influenza, commonly known as the flu, is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptoms begin one to four (typically two) days after exposure to the virus and last for about two to eight days. Getting vaccinated every year is the best way to avoid getting sick with the flu. The flu, common cold and COVID-19 have similar symptoms. The flu and COVID-19 can be severe, but colds rarely are. What is the flu (influenza)? The flu is an illness you get from the influenza virus. Flu, also called influenza, is an infection of the nose, throat and lungs, which are part of the respiratory system. The flu is caused by a virus. Influenza viruses are different from the stomach flu viruses that cause diarrhea and vomiting. Most people with the flu get better on their own. In a typical year, flu season occurs from fall to early spring — and with it comes sniffling, sneezing, coughing, fatigue, and all the familiar trappings of the flu. The severity of the illness. Where is flu active today? Get Cold & Flu Activity Report for San Jose, CA (95160). Check Cold & Flu conditions in your area. Flu is a contagious respiratory illness that infect the nose, throat, and sometimes the lungs. Learn about the current flu season and find resources related to flu surveillance and past seasons. Learn more about who is at higher risk of developing potentially serious flu complications. The California Respiratory Virus Dashboard shows statewide and regional, weekly respiratory virus data. It provides an overview of activity and severity for flu, RSV, and COVID-19. A weekly influenza surveillance report prepared by the Influenza Division. All data are preliminary. FluView Interactive, influenza surveillance data the way you want it. Purpose and Methods. During the fall and winter respiratory virus season, two types of flu can circulate: Influenza A viruses can mutate to cause novel viruses. Novel viruses are viruses that have not infected humans before. This means that humans have no immunity to novel viruses, so they cannot quickly fight them off. Flu is spread when you inhale droplets in the air that contain the flu virus, make direct contact with respiratory secretions through sharing drinks or utensils, or handle items contaminated by.