How are influenza viruses transmited from human to human?
Seasonal and pandemic influenza are highly contagious diseases and are spread primarily by coughing and sneezing. When they sneeze, people release tiny droplets of fluid into the air. Those tiny droplets can fly up to 1 metre and infect persons nearby by reaching susceptible cells of the respiratory tract. The virus can also be spread indirectly when a person touches objects such as door knobs, tap handles or phones that are contaminated with the influenza virus through sneezing or touch. The influenza virus may remain infectious on surfaces for up to three months in cool temperatures, and in water at 0 °C for more than 30 days or in water at 22 °C for up to 4 days.
People who are infected with an influenza virus can pass along the virus even before the symptoms kick in, and may remain infectious for about five days after they start sneezing. Young children can be infectious even longer and seven days is no exception.