The role of genetics in influenza is not well researched, but it may be a factor in influenza mortality. Epidemiology
Influenza is typically characterized by seasonal epidemics and sporadic pandemics. Most of the burden of influenza is a result of flu seasons caused by IAV and IBV. Among IAV subtypes, H1N1 and H3N2 currently circulate in humans and are responsible for seasonal influenza. Cases disproportionately occur in children, but most severe causes are among the elderly, the very young, and the immunocompromised. In a typical year, influenza viruses infect 5–15% of the global population, causing 3–5 million cases of severe illness annually and accounting for 290,000–650,000 deaths each year due to respiratory illness. 5–10% of adults and 20–30% of children contract influenza each year. The reported number of influenza cases is usually much lower than the actual number of cases.During seasonal epidemics, it is estimated that about 80% of otherwise healthy people who have a cough or sore throat have the flu. Approximately 30–40% of people hospitalized for influenza develop pneumonia, and about 5% of all severe pneumonia cases in hospitals are due to influenza, which is also the most common cause of ARDS in adults. In children, influenza is one of the two most common causes of ARDS, the other being the respiratory syncytial virus. About 3–5% of children each year develop otitis media due to influenza. Adults who develop organ failure from influenza and children who have PIM scores and acute renal failure have higher rates of mortality.
Pharmaceutical measures are effective but may not be available in the early stages of an outbreak.In health care settings, infected individuals may be cohorted or assigned to individual rooms. Protective clothing such as masks, gloves, and gowns is recommended when coming into contact with infected individuals if there is a risk of exposure to infected bodily fluids. Keeping patients in negative pressure rooms and avoiding aerosol-producing activities may help, but special air handling and ventilation systems are not considered necessary to prevent the spread of influenza in the air. In residential homes, new admissions may need to be closed until the spread of influenza is controlled. When discharging patients to care homes, it is important to take care if there is a known influenza outbreak.Since influenza viruses circulate in animals such as birds and pigs, prevention of transmission from these animals is important. Water treatment, indoor raising of animals, quarantining sick animals, vaccination, and biosecurity are the primary measures used. Placing poultry houses and piggeries on high ground away from high-density farms, backyard farms, live poultry markets, and bodies of water helps to minimize contact with wild birds. Closure of live poultry markets appears to the most effective measure and has shown to be effective at controlling the spread of H5N1, H7N9, and H9N2.