Dr.Charles Patrick 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, 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.
Influenza, or the "flu," is a illness of the breathing
system (respiratory system) and muscles caused by a virus. While a vaccine is
available to prevent the flu, its effectiveness varies according to the degree
of match between the viral strains used to prepare the vaccine and those strains
actually in circulation in a given year. Not everyone receives the flu vaccine, and even
some of those who do can develop symptoms of the flu.
Mild cases of the flu may seem like common colds. But most cases of the flu
can be distinguished from colds because the symptoms (cough, muscle aches and
pains, sore throat, fatigue, and headache)
are more severe than those of the common cold. Flu symptoms also tend to occur suddenly and include high fevers
(temperatures of 101 degrees F or more).
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 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. 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%-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 (termed novel H1N1
influenza A swine flu, often 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.
What are the causes of the flu?
The flu (influenza) viruses
Influenza viruses cause the flu and are divided into three types, designated A, B, and C. Influenza types A and B are responsible for epidemics of respiratory illness that occur almost every winter and are often associated with increased rates of hospitalization and death. Influenza type C differs from types A and B in some important ways. Type C infection usually causes either a very mild respiratory illness or no symptoms at all; it does not cause epidemics and does not have the severe public-health impact of influenza types A and B. Efforts to control the impact of influenza are aimed at types A and B, and the remainder of this discussion will be devoted only to these two types.
Influenza viruses continually change over time, usually by mutation (change in the viral RNA). This constant changing often enables the virus to evade the immune system of the host (humans, birds, and other animals) so that the host is susceptible to changing influenza virus infections throughout life. This process works as follows: a host infected with influenza virus develops antibodies against that virus; as the virus changes, the "first" antibody no longer recognizes the "newer" virus and infection can occur because the host does not recognize the new flu virus as a problem until the infection is well under way. The first antibody developed may, in some instances, provide partial protection against infection with a new influenza virus. In 2009, almost all individuals had no antibodies that could recognize the novel H1N1 virus immediately.
Type A viruses are divided into types based on differences in two viral surface
proteins called the hemagglutinin (H) and the neuraminidase (N). There are at
least 16
known H subtypes and nine known N subtypes. These surface proteins can occur in
many combinations. When spread by droplets or direct contact, the virus, if not
killed by the host's immune system, replicates in the respiratory tract and
damages host cells. In people who are immune compromised (for example, pregnant individuals, infants, cancer patients, asthma patients, people with pulmonary disease and many others), the virus can cause viral pneumonia or stress the individual's system to make them more susceptible to bacterial infections, especially bacterial pneumonia. Both pneumonia types, viral and bacterial, can cause severe disease and sometimes death.
Antigenic shift and drift
Influenza type A viruses undergo two kinds of changes. One is a series
of mutations that occurs over time and causes a gradual evolution of the
virus. This is called antigenic "drift." The other kind of
change is an abrupt change in the hemagglutinin and/or the neuraminidase
proteins. This is called antigenic "shift." In this case, a new
subtype of the virus suddenly emerges. Type A viruses undergo both kinds
of changes; influenza type B viruses change only by the more gradual
process of antigenic drift and therefore do not cause pandemics.
A diagram that illustrates both antigenic shift and drift can be found at http://www.medicinenet.com/swine_flu/page5.htm and shows how both mechanisms can lead to antigenically diverse virus strains. The 2009 pandemic-causing H1N1 virus is a classic example of antigenic shift. The U.S. Centers for Disease Control and Prevention (CDC) has indicated that novel H1N1 swine flu has an RNA genome that contains five RNA strands derived from various swine flu strains, two RNA strands from bird flu strains, and only one RNA strand from human flu strains. They suggest mainly antigenic shifts over about 20 years have led to the development of novel H1N1 flu virus.
Listeria is a type of bacteria that can cause food poisoning. Listeriosis symptoms include diarrhea, nausea and fever. Pregnant women are 20 times more likely than other healthy adults to get listeriosis. Listeria infection is treated with antibiotics.
Herpes simplex infections are common and when they appear around the mouth and lips, people often refer to them as "cold sores" and "fever blisters." Canker sores are different than cold sores. Air droplets can spread the virus, as can direct contact with the fluid from the blisters. Cold sore treatment include over-the-counter medication as well as prescription medications.
Bronchitis is a disease of the respiratory system in which the bronchial passages become inflamed. There are two types of bronchitis, acute and chronic. Symptoms of acute bronchitis include frequent cough with mucus, lack of energy, wheezing, and possible fever. Treatment may require medication such as bronchial inhalers and predinsone. Supportive treatment is focused on relieving the symptoms with fever reducers, cough suppressants, and rest. Treatment may be more aggressive in patients with pre-existing conditions such as empyema, COPD, or cigarette smoking.
An upper respiratory infection is a contagious infection of the structures of the upper respiratory tract, which includes the sinuses, nasal passages, pharynx, and larynx. Common causes of an upper respiratory infection include bacteria and viruses such as rhinoviruses, group A streptococci, influenza, respiratory syncytial, whooping cough, diphtheria, and Epstein-Barre. Examples of symptoms of upper respiratory infection include sneezing, sore throat, cough, fever, and nasal congestion. Treatment of upper respiratory infection are generally with OTC medication and home remedies.
The Eustachian tube is a membrane lined tube that connects the middle ear space to the back of the nose. Problems include partial or complete blockage which can cause popping, clicking, and ear fullness. Allergies, sinus and ear infections, or the common cold can cause this blockage, while altitude changes can cause symptoms in those persons with Eustachian tube problems. Treatment includes several maneuvers (swallowing, chewing gum, yawning etc.), which can be done to improve Eustachian tube function.
Bird flu (avian flu, avian influenza) infection in humans may result from contact with infected poultry. There is a vaccine to prevent human infection with the H5N1 strain of the avian flu virus.
Mercury is a naturally occurring element found in water, soil, and the air. Mercury is also contained in some fish, some of the products we use in the home, school, or dentist. Information about sources of mercury exposure, potential health effects, symptoms of exposure, fish that may contain mercury, consumer products that contain mercury, and ways to reduce your exposure to mercury is important for the health of you, and your family.
Plague is an infectious disease caused by the Yersinia pestis bacteria, which is primarily found in rodents the fleas that feed off of them. The bacteria are passed to humans through flea or rodent bites. There are three forms of plague: bubonic, septicemic, and pneumonic. The symptoms and method of transmission vary with each form of plague. Plague can be treated with antibiotics.
Chronic bronchitis is a cough that occurs daily with production of sputum that lasts for at least three months, two years in a row. Causes of chronic bronchitis include cigarette smoking, inhaled irritants, and underlying disease processes (such as asthma, or congestive heart failure). Symptoms include cough, shortness of breath, and wheezing. Treatments include bronchodilators and steroids. Complications of chronic bronchitis include COPD and emphysema.
Before treating a cold, the flu, or allergies with over-the-counter (OTC) medications, it's important to know what's causing the symptoms, which symptoms one wishes to relieve, and the active ingredients in the OTC product. Taking products that only contain the medications needed for relieving your symptoms prevents ingestion of unnecessary medications and reduces the chances of side effects.
Novel H1N1 influenza A virus infection (swine flu) is an infection that generally is transferred from an infected pig to a human, however there have been reported cases where infection has occured with no contact with infected pigs. Symptoms of swine flu are "flu-like" and include fever, cough, and sore throat. Treatment is generally with the antibiotics oseltamivir (Tamiflu) or zanamivir (Relenza).
Fatigue can be described in various ways. Sometimes fatigue is described as feeling a lack of energy and motivation (both mental and physical). The causes of fatigue are generally related to a variety of conditions or diseases for example, anemia, mono, medications, sleep problems, cancer, anxiety, heart disease, drug abuse, and more. Treatment of fatigue is generally directed toward the condition or disease that is causing the fatigue.
Drug resistance (antimicrobial resistance) is the ability of bacteria, fungi, parasites, and viruses to grow, even in the presence of a drug that would normally kill it (or limit it's growth). Drug resistance is a growing problem, particularly for infections such as MRSA, VRE (vancomycin-resistant enterococci), tuberculosis, HIV, STDs, gonorrhea, flu, pneumonia, malaria, E. coli, salmonella, Campylobacter, which causes diarrhea and gastroenteritis. Learn how to protect yourself from resistance to drugs.
Adenovirus infection, particularly Ad14, or the "killer cold virus" has been on the increase in the past two years. Symptoms range from those experienced with colds, sore throat, bronchitis, pneumonia, diarrhea, pinkeye, fever, bladder infection, and neurological conditions. Diagnosis and treatment options need to be discussed with your physician.
Reye's syndrome (RS, or Reye syndrome) is a sudden, sometimes fatal, disease of the brain with degeneration of the liver. Reye syndrome occurs in children and comes after the chickenpox or an influenza-type illness, is also associated with taking medications containing aspirin. Symptoms include vomiting, listlessness, irritability or combativeness, confusion, delirium, delusions, convulsions, and loss of consciousness. Treatment depends on early diagnosis and focuses on protecting the brain against irreversible damage by reducing brain swelling, reversing the metabolic injury, preventing complications in the lungs, and anticipating cardiac arrest.
Adult-onset asthma is asthma that is diagnosed in people over 20 years of age. Symptoms include wheezing, coughing, shortness of breath and difficulty breathing. Treatment may involve anti-inflammatory medications or bronchodilators.
The most common taste disorder is phantom taste perception; that is, a lingering, often unpleasant taste even though you have nothing in your mouth. We also can experience a reduced ability to taste sweet, sour, bitter, salty, and umami, a condition called hypogeusia. Some people cannot detect any tastes, which is called ageusia.
Severe acute respiratory syndrome (SARS) is a respiratory disease caused by the coronavirus SARS-CoV. Symptoms include fever and shortness of breath. Patients with SARS often require oxygen and severe cases require mechanical ventilation.
If you have a COPD such as emphysema, avoiding chronic bronchitis and colds is important to avoid a more severe respiratory infection such as pneumonia. Avoiding cigarette smoking, practice good hygeine, stay away from crowds, and alerting your healthcare provider if you have a sinus infection or cold or cough that becomes worse. Treatment options depend upon the severity of the emphysema, bronchitis, or cold combination.
Exercise-induced asthma is asthma triggered by vigorous exercise. Symptoms include coughing, shortness of breath, chest tightness, wheezing, and fatigue while exercising. Preventing exercise-induced asthma attacks involves using inhaled medicines before exercising, performing warm-up exercises and cooling down afterward, avoiding exercising outdoors when pollen counts are high, restricting exercise when you have a viral infection, and wearing a mask over your nose and mouth when exercising in cold weather.
Pregnant and women who are breastfeeding are encouraged to receive the seasonal flu shot as well as the 2009 H1N1 influenza (swine flu) vaccine. H1N1 flu is treated with the medications Tamiflu�® (oseltamivir) or Relenza�® (zanamivir). Pregnant women should not receive the H1N1 attenuated nasal spray vaccine. Possible side effects of the H1N1 flu vaccine include muscle aches, fever, nausea, tiredness, or headache.
A bacterium, Yersinia pestis, causes the disease in animals and humans.
Plague is a disease that is transmitted from infected animals, usually by fleas, to humans.
Plague then may be transmitted from humans to others by direct contact or by touching or breathing droplets that contain the bacterium,
Yersinia pestis. Untreated plague causes much suffering and deaths in humans.
Symptoms of plague vary and are grouped into three types:
Bubonic: The lymph nodes become swollen, tender, and are termed
buboes. The patient may also develop fever, chills,
and weakness.
Septicemic: In general, septicemic plague patients do not develop buboes.
Instead symptoms may include fever, chills, weakness, bleeding under the skin, abdominal pain, and septic shock with low blood pressure.
Pneumonic: Shortness of breath,
cough (sometimes with bloody sputum), and chest pain quickly ...