Charles Patrick Davis, MD, PhD
Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.
Melissa Conrad Stöppler, MD
Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.
- Flu (influenza, conventional, and H1N1) facts
- What is influenza?
- What are the causes of the flu?
- What are flu symptoms in adults and in children?
- How is the flu diagnosed?
- What is the key to flu prevention?
- Are there any flu shot or nasal spray vaccine side effects in adults or in children?
- Why should the influenza vaccine be taken every year?
- What are some treatments an individual can do at home for the flu?
- When should a person go to the emergency department for the flu?
- Who should receive the flu vaccine, and who has the highest risk factors? When should someone get the flu shot?
- What is the prognosis (outlook) and complications for patients who get the flu?
- What is the bird (avian) flu?
- Do antiviral agents protect people from the flu?
- Is it safe to get a flu shot that contains thimerosal?
- Where can I find additional information about the flu?
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- Patient Comments: Flu (Influenza) - Side effects
Flu (influenza, conventional, and H1N1) facts
- Influenza, commonly called "the flu," is caused by viruses that infect the respiratory tract.
- Influenza viruses are divided into three types, designated A, B, and C, with influenza A types usually causing the most problems in humans.
- Most people who get the conventional or seasonal flu recover completely in one to two weeks, but some people develop serious and potentially life-threatening medical complications, such as pneumonia.
- Much of the illness and death caused by conventional or seasonal influenza can be prevented by annual influenza vaccination.
- Influenza A undergoes frequent antigenic changes that require new vaccines to be developed and people to obtain a new vaccination every year. New vaccine technology is being developed.
- In April 2009, a new flu virus termed novel H1N1 swine flu developed in Mexico, rapidly spread worldwide, and caused the WHO to declare a flu pandemic. Eventually, the WHO declared the pandemic over in 2010. In 2012, a new type of flu strain developed, H3N2v, but has not developed into any epidemic situations currently.
- Like the influenza virus, drug treatments are constantly changing and improving, but currently, timely vaccination is still considered to be the best defense against the flu. However, the CDC considers antivirals an important adjunct to flu vaccine in the control of the disease process.
- People should be aware that flu pandemics can cause severe flu symptoms and sometimes death in many individuals who may be more susceptible to the pandemic flu than the conventional flu; however the previous pandemic flu virus (H1N1) has been available in vaccines and is considered part of the conventional circulating flu viruses.
- Individuals should check with their doctors to determine if they are considered to be at higher risk of getting severe flu symptoms than the normally healthy population.
What is influenza?
Influenza, commonly called "the flu," is an illness caused by RNA viruses that infect the respiratory tract of many animals, birds, and humans. In most people, the infection results in the person getting fever, cough, headache, and malaise (tired, no energy); some people also may develop a sore throat, nausea, vomiting, and diarrhea. The majority of individuals has symptoms for about one to two weeks and then recovers with no problems. However, compared with most other viral respiratory infections, such as the common cold, influenza (flu) infection can cause a more severe illness with a mortality rate (death rate) of about 0.1% of people who are infected with the virus.
The above is the usual situation for the yearly occurring "conventional" or "seasonal" flu strains. However, there are situations in which some flu outbreaks are severe. These severe outbreaks occur when a portion of the human population is exposed to a flu strain against which the population has little or no immunity because the virus has become altered in a significant way. These outbreaks are usually termed epidemics. Unusually severe worldwide outbreaks (pandemics) have occurred several times in the last hundred years since influenza virus was identified in 1933. By an examination of preserved tissue, the worst influenza pandemic (also termed the Spanish flu or Spanish influenza) occurred in 1918 when the virus caused between 40-100 million deaths worldwide, with a mortality rate estimated to range from 2% to 20%.
In April 2009, a new influenza strain against which the world population has little or no immunity was isolated from humans in Mexico. It quickly spread throughout the world so fast that the WHO declared this new flu strain (first termed novel H1N1 influenza A swine flu, often later shortened to H1N1 or swine flu) as the cause of a pandemic on June 11, 2009. This was the first declared flu pandemic in 41 years. Fortunately, there was a worldwide response that included vaccine production, good hygiene practices (especially hand washing) were emphasized, and the virus (H1N1) caused far less morbidity and mortality than was expected and predicted. The WHO declared the pandemic's end on Aug. 10, 2010, because it no longer fit into the WHO's criteria for a pandemic.
Haemophilus influenzae is a bacterium that was incorrectly considered to cause the flu until the virus was demonstrated to be the correct cause in 1933. This bacterium can cause lung infections in infants and children, and it occasionally causes ear, eye, sinus, joint, and a few other infections, but it does not cause the flu.
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