Factors that influence the spread of influenza center on exposure to the virus in aerosol form. The three kinds of influenza spread at different rates, but the all of them are spread through the coughing and sneezing of infected individuals. Hygienic precautions like hand washing and avoiding proximity to sick people during the height of their infection reduces the spread of the virus. Vaccination can slow down influenza infection rates and protect vulnerable populations.
Influenza is an infectious respiratory virus spread by aerosol droplets emitted by those infected. Infection comes from direct inhalation into the lungs and exposure through the nose and mouth. The spread of influenza from one person to another can occur even before infected individuals experience flu symptoms, but is worst during the height of fever. Children spread influenza more efficiently than do adults. The virus needs moisture and will dry out quickly if exposed to ultraviolet radiation or dry air, which may account for the prevalence of influenza during humid and darker winter weather.
In moist droplets, the influenza virus can survive outside of the body for a time on things like railings, dishes, and doorknobs. Through these it is spread by hand-to-mouth contact when someone touches an object contaminated with the aerosols and then touches his or her own mouth. Sharing cups and utensils with infected individuals increases the risk of infection. For this reason, consistent hand washing with soap and water and properly washing dishes and utensils helps reduce the spread of influenza.
Two major factors in the spread of influenza depend on the strain of the virus and its rate of mutation, since flu strains constantly mutate as they compete with host immune systems. Influenza B and C are milder forms, but influenza A produces more serious cases of illness. Pandemics occur when a virulent strain of flu infects millions of people around the world, typically due to new mutations that have migrated from other animals to humans. The 1918 Spanish Flu outbreak, for instance, resulted from a mutated strain related to avian influenza that caused hemorrhage and other unusually severe symptoms.
Vaccination prevents the spread of influenza in common forms, particularly of influenza B, but it does not guarantee protection from the spread of new mutations. It is recommended for the elderly, who are at greater risk of serious complications. Hand washing, covering the mouth and nose while sneezing, and avoiding contact with individuals during the peak of their infections are important. If flu sufferers rest at home and avoid public places until recovery, they are less likely to expose others to the virus.