For just about everyone, the flu conjures up unpleasant memories of days spent lying in bed, suffering from fever, fatigue, and congestion. Influenza isn’t just unpleasant—it’s one of the leading causes of death in the United States, and costs nearly a trillion dollars a year in medical costs and lost earnings. With flu season right around the corner, Stacker compiled 25 essential flu facts from a range of authoritative healthcare sources to help make sure you’re prepared.
The flu can take a number of forms, from the deadly 1918 Spanish flu to the more recent 2009 swine flu outbreak. The two main types of influenza that cause seasonal epidemics are influenza A and B, and because the flu virus can evolve so rapidly, the World Health Organization closely monitors influenza in over 100 countries to predict which virus will dominate the upcoming flu season.
While the flu vaccine is the best method for preventing the flu, recent medical studies have uncovered a number of remedies that can help shorten the length of the illness and relieve symptoms if you do catch a virus. These flu facts come from the Centers for Disease Control and Prevention (CDC), the World Health Organization (WHO), and peer-reviewed medical studies on influenza.
In 2015, 2.1% of all deaths in the United States were caused by influenza and pneumonia. This places influenza among the ten leading causes of death in the country.
A 2007 study in the journal Vaccine estimated that the U.S. loses $87.1 billion each year due to the flu. This includes direct medical costs of $10.4 billion annually and another $16.3 billion in lost earnings due to illness and death.
History’s deadliest flu epidemic struck in 1918, infecting one in five people around the world. The influenza epidemic killed an estimated 50 million people worldwide—more than three times the number of people who died during World War I.
CDC analysis of the 2015-2016 flu season, based on vaccine coverage, effectiveness, and influenza hospitalization rates, concluded that approximately 5.1 million cases of influenza were prevented by the vaccine. Furthermore, the vaccine prevented 2.5 million medical visits and 71,000 hospitalizations.
Every year, the World Health Organization coordinates an international effort to design a new flu vaccine. The Global Influenza Surveillance and Response System (GISRS) collects data from over 100 countries on influenza, and five laboratories, located in the U.S., United Kingdom, Australia, Japan, and China, predict and design a flu vaccine.
Because the flu virus is constantly evolving, and multiple viruses often circulate in a single flu season, the vaccine’s effectiveness can vary. The World Health Organization has to predict what viruses to include in the vaccine each year. However, the CDC emphasizes that a less than optimal match can still protect against related viruses, especially for those at the greatest risk of flu complications.
It takes approximately two weeks for the flu vaccine to provide immunity, so the CDC recommends that everyone over 6 months of age receives a flu vaccine by the end of October—before the height of flu season.
It’s never too late to get a flu shot—the Advisory Committee on Immunization Practices reports that in 80% of flu seasons since 1976, the peak flu activity is in January or later, and in 60% of seasons, the peak was in February or later.
Babies can receive the flu vaccine starting at age 6 months. Based on an analysis of the 2016-2017 flu season, the CDC found that 76.3% of children 6 months to 23 months old were vaccinated representing the highest rate for any age group.
During the 2016-2017 flu season, the CDC found that only 33.6% of adults aged 18 to 49 received a flu vaccine, the lowest vaccination rate for any age group.
Contrary to popular belief, you cannot catch the flu from a flu vaccine—the viruses in the vaccine are either inactivated or weakened so that they cannot cause influenza. In fact, some flu vaccines contain no flu viruses at all. In spite of that, the myth that vaccines can cause illness dates back to the birth of the vaccine in the 18th century.
The CDC recommends a few good health habits to stop the spread of germs. First, avoid close contact with people who are sick, and avoid touching your eyes, nose, or mouth. Second, if you are sick, stay home and always cover your cough. Finally, make sure to wash your hands.
Hygiene is important to prevent the spread of the influenza virus. Both washing hands with soap and water and using hand sanitizer are effective at eliminating the virus, but a 2009 study published in the journal Clinical Infectious Diseases found that soap and water were statistically superior to alcohol-based hand rubs, by a small margin.
Once someone has been exposed to the influenza virus, it typically incubates for one to four days before symptoms appear. The CDC reports that adults may be infectious one day before symptoms develop and for up to a week after becoming sick.
Unlike a cold, which may develop slowly, the influenza virus has a rapid onset that typically includes a fever. Flu symptoms also include fatigue, aches, and a runny or stuffy nose.
Serious flu complications can be deadly. It is important to know the warning signs that you should seek medical attention. Children who have difficulty breathing, a bluish skin color, severe lethargy, or a fever with a rash should receive immediate medical attention. Adults that show signs of dizziness, confusion, severe vomiting, or difficulty breathing should also see a doctor.
A 2000 study published in the Journal of Alternative And Complementary Medicine found that drinking five to six cups of echinacea herbal tea at the onset of flu symptoms can help relieve symptoms and shorten the course of the illness.
A 1999 study evaluated the effectiveness of Vitamin C in alleviating the symptoms of virus-induced respiratory infections. The results demonstrated that flu and cold symptoms decreased by 85% when the test group received a megadose—1000 mg three times a day—of Vitamin C.
In 2012, a study published in Clinical Nutrition found that continuous use of aged garlic extract could reduce flu symptoms and result in 58% fewer days of work or school missed due to illness.
Prescription antiviral drugs can alleviate flu symptoms and shorten the course of the illness by 1 or 2 days, as well as prevent serious complications like pneumonia. Doctors may prescribe antiviral drugs for high-risk groups and those with severe flu symptoms.
The CDC reports that uncomplicated cases of influenza typically resolve after 3 to 7 days, though malaise and coughing can continue for another week. The vast majority of influenza cases do not require medical intervention—they just require rest and time.