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, 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.
If you've got fever, cough, or one of the other symptoms of the flu, you may
be wondering if you have contracted the H1N1 swine flu virus. The reality is
that it isn't possible to know unless specialized testing is ordered, and for
uncomplicated cases of the flu in non-hospitalized patients, routine testing for
the H1N1 virus is not being carried out.
Experts recommend that people who suspect that they have H1N1 infection stay
home and avoid contact with other people. The only time you should leave home is
to access medical care if needed. That said, it is important to remember that
the vast majority of flu cases (even H1N1 cases) produce only a mild illness for
which doctor's visits and/or antiviral drugs are not necessary. So, the presence
of cough and fever in an individual who is not at high risk for complications
(see below) and who does not have warning signs of a medical emergency should
not be a reason to visit an ER. The emergency department should be used for the
treatment of people who are very sick or who have life-threatening emergencies
(listed below). If you're in doubt, a call to your health-care practitioner can
help you decide whether or not you need to access medical care.
What is swine flu (novel H1N1 influenza A swine flu)?
Swine flu (swine influenza) is a respiratory disease caused by viruses (influenza viruses) that infect the respiratory tract of pigs and result in nasal secretions, a barking-like cough, decreased appetite, and listless behavior. Swine flu produces most of the same symptoms in pigs as human flu produces in people. Swine flu can last about
one to two weeks in pigs that survive. Swine influenza virus was first isolated from pigs in 1930 in the U.S. and has been recognized by pork producers and veterinarians to cause infections in pigs worldwide. In a number of instances, people have developed the swine flu infection when they are closely associated with pigs (for
example, farmers, pork processors), and likewise, pig populations have occasionally been infected with the human flu infection. In most instances, the cross-species infections (swine virus to man; human flu virus to pigs) have remained in local areas and have not caused national or worldwide infections in either pigs or humans. Unfortunately, this cross-species situation with influenza viruses has had the potential to change.
Investigators think the 2009 swine flu strain, first seen in Mexico, should be termed
novel H1N1 flu since it is mainly found infecting people and exhibits two main surface antigens, H1 (hemagglutinin type 1) and N1 (neuraminidase type1). Recent investigations show the eight RNA strands from novel H1N1 flu have one strand derived from human flu strains, two from avian (bird) strains, and five from swine strains.
Why is swine flu (H1N1) now infecting humans?
Many researchers now consider that two main series of events can lead to swine flu (and also avian or bird flu) becoming a major cause for influenza illness in humans.
First, the influenza viruses (types A, B, C) are enveloped RNA viruses with a segmented genome; this means the viral RNA genetic code is not a single strand of RNA but exists as
eight different RNA segments in the influenza viruses. A human (or bird) influenza virus can infect a pig respiratory cell at the same time as a swine influenza virus; some of the replicating RNA strands from the human virus can get mistakenly enclosed inside the enveloped swine influenza virus. For example, one cell could contain
eight swine flu and eight human flu RNA segments. The total number of RNA types in one cell would be 16;
four swine and four human flu RNA segments could be incorporated into one particle, making a viable
eight RNA segmented flu virus from the 16 available segment types. Various combinations of RNA segments can result in a new subtype of virus (known as antigenic shift) that may have the ability to preferentially infect humans but still show characteristics unique to the swine influenza virus (see Figure 1). It is even possible to include RNA strands from birds, swine, and human influenza viruses into one virus if a cell becomes infected with all three types of influenza (for example,
two bird flu, three swine flu, and three human flu RNA segments to produce a viable
eight-segment new type of flu viral genome). Formation of a new viral type is considered to be antigenic shift; small changes in an individual RNA segment in flu viruses
are termed antigenic drift and result in minor changes in the virus. However, these can accumulate over time to produce enough minor changes that cumulatively change the virus' antigenic makeup over time (usually years).
Second, pigs can play a unique role as an intermediary host to new flu types because pig respiratory cells can be infected directly with bird, human, and other mammalian flu viruses. Consequently, pig respiratory cells are able to be infected with many types of flu and can function as a "mixing pot" for flu RNA segments (see Figure 1). Bird flu viruses, which usually infect the gastrointestinal cells of many bird species, are shed in bird feces. Pigs can pick these viruses up from the environment and seem to be the major way that bird flu virus RNA segments enter the mammalian flu virus population.
Pneumonia is inflammation of one or both lungs with consolidation. Pneumonia is frequently but not always due to infection. The infection may be bacterial, viral, fungal or parasitic. Symptoms may include fever, chills, cough with sputum production, chest pain, and shortness of breath.
Most sore throats are caused by viruses or mechanical causes (such as mouth breathing) and can be treated successfully at home. However, a person should be seen by a health care professional if they have a sore throat that has a rapid onset, and is associated with a fever or tenderness of the front of the neck; a sore throat that causes the person to have difficulty swallowing (not just pain swallowing) or breathing; or if a sore throat lasts for more than a week.
Diarrhea is a change is the frequency and looseness of bowel movements. Cramping, abdominal pain, and the sensation of rectal urgency are all symptoms of diarrhea. Absorbents and anti-motility medications are used to treat diarrhea.
Headaches can be divided into two categories: primary headaches and secondary headaches. Migraine headaches, tension headaches, and cluster headaches are considered primary headaches. Secondary headaches are caused by disease. Headache symptoms vary with the headache type. Over-the-counter pain relievers provide short-term relief for most headaches.
Chronic cough is a cough that does not go away and is generally a symptom of another disorder such as asthma, allergic rhinitis, sinus infection, cigarette smoking, GERD, postnasal drip, bronchitis, pneumonia, medications, and less frequently tumors or other lung disease. Treatment of chronic cough is dependant upon the cause.
Nausea is an uneasiness of the stomach that often precedes vomiting. Nausea and vomiting are not diseases, but they are symptoms of many conditions. The causes of vomiting differ according to age, and treatment depends upon the cause of nausea and vomiting.
Although a fever technically is any body temperature above the normal of 98.6 degrees F. (37 degrees C.), in practice a person is usually not considered to have a significant fever until the temperature is above 100.4 degrees F (38 degrees C.). Fever is part of the body's own disease-fighting arsenal: rising body temperatures apparently are capable of killing off many disease- producing organisms.
Epilepsy is a brain disorder in which the person has seizures. There are two kinds of seizures, focal and generalized. There are many causes of epilepsy. Treatment of epilepsy (seizures) depends upon the cause and type of seizures experienced.
Influenza (flu) is a respiratory illness caused by a virus. Flu symptoms include fever, cough, sore throat, runny nose, headache, fatigue, and muscle aches. The flu may be prevented with an annual influenza vaccination.
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.
Guillain-Barre Syndrome is an autoimmune disease of the nervous system due to damage to the myelin sheath around nerves. It is the most acquired nerve disease (neuropathy) and usually follows a virus infection but can also be associated with immunizations, surgery, and childbirth. The cause is unknown but appears to be related to autoimmune reaction. Symptoms include weakness beginning in the legs and progressing upward, lost reflexes, and in severe cases breathing can be affected. Patients can expect a slow but progressive recovery over several months maintaining vital functions and passively exercising the muscles. Plasmapheresis (removing toxic substances from the blood) has been shown to improve outcome and shorten the disease as well as intravenous immunoglobulin.
Kids get headaches and migraines too. Many adults with headaches started having them as kids, in fact, 20% of adult headache sufferers say their headaches started before age 10, and 50% report their headaches started before age 20.
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.
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.
Pregnancy and H1N1 influenza (swine flu) introduction
These questions and answers have been updated to include new information on
2009 H1N1 flu in pregnant women. Both seasonal and 2009 H1N1 flu viruses will
circulate during the 2009-2010 flu season. A pregnant woman who thinks she has
the flu should call her doctor right away to see if treatment with an antiviral
medicine is needed. The medicine is most helpful if it is started soon after the
pregnant woman becomes sick. The latest advice for getting seasonal and 2009
H1N1 vaccines during pregnancy is also included.
What if I am pregnant and I get 2009 H1N1?
Call your doctor right away if you have
flu symptoms or if you have close
contact with someone who has the flu. Pregnant women who get sick with 2009 H1N1
can have serious health problems. They can get sicker than other people who get
2009 H1N1 flu. Some pregnant women sick with
2009 H1N1 have had
early labor an...
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