Stages of the Flu

By jolene

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The flu, or influenza, is an infectious condition caused by the influenza virus. It is one of the commonest infectious disease that is highly contagious. It usually occurs in seasonal epidemics and presents with various symptoms that range from mild fatigue to severe respiratory symptoms and even death.

The United States Centers for Disease Control and Prevention (CDC) has documented that the seasonal influenza accounted for 34,400 to 57,300 deaths throughout the 2018 to 2019 season. Influenza is a condition that results in significant absence from school and work. The rates of mortality are highest among the elderly and infants.

1. Influenza through the Years

Throughout the years, lethal influenza strains have emerged periodically. In the last century, these deadly strains have resulted in three global pandemics with the worst one occurring in 1918. Known as the Spanish flu, this pandemic resulted in an estimated 20 to 50 million deaths globally with 549,000 deaths occurring in the United States alone. Influenza not only affects humans but also different animal species. While some are species specific, there are some strains that spread from animals to humans. For example, avian influenza or bird flu is an influenza strain that mainly affects birds but can spread to humans. Swine influenza is a strain from pigs. In 2009, the influenza pandemic was caused by a strain with a combination of avian, swine, and human segments.