Mary D. Nettleman, MD, MS, MACP is the Chair of the Department of Medicine at Michigan State University. She is a graduate of Vanderbilt Medical School, and completed her residency in Internal Medicine and a fellowship in Infectious Diseases at Indiana University.
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.
Bird flu is caused by strains of the influenza virus
that have evolved to be specially adapted to enter avian cells. There are three
main types of influenza: A, B, and C. The virus that causes bird flu is an
influenza A type with eight RNA strands that make up its genome. Influenza
viruses are further classified by analyzing two proteins on the surface of the
virus. The proteins are called hemagglutinin (H) and neuraminidase (N). There
are many different types of hemagglutinin and neuraminidase proteins. The
current highly pathogenic bird flu virus has type 5 hemagglutinin and type 1
neuraminidase. Thus, it is a "H5N1" influenza A virus.
There are many types of
influenza viruses, and most prefer to live in a limited number of animals. Thus,
swine flu primarily infects swine and bird flu primarily infects birds. Human
influenza is best adapted to humans. A few cases may occur in an accidental
host, such as when people who have extensive contact with sick birds get the
bird flu. In addition to humans and birds, we know that pigs, tigers, leopards,
ferrets, and domestic cats can sometimes be infected with avian influenza
viruses.
Influenza viruses mutate easily and often. These mutations can arise
spontaneously in a single virus or can occur when two different influenza
strains get close enough together to exchange genetic material. There are two
major types of mutations in influenza viruses: antigenic shifts, where large RNA
segments are interchanged between different influenza virus type, and antigenic
shifts, where small RNA sequences are changed. The antigenic shifts are usually
responsible for developing new strains. For example, the 2009 swine flu pandemic
was caused by a virus that included genetic material from pig influenza, avian
influenza, and human influenza strains. New mutations can allow the virus to
evade the body's immune system and makes older vaccines ineffective. In 2011,
one strain of the highly pathogenic avian influenza virus mutated in this way,
making the existing vaccine used against avian flu ineffective against the new
strain. Sometimes a flu virus will mutate in a way that makes it able to infect
a new species.
Serious pandemic influenza occurs when a relatively new strain of
the influenza virus arises that is highly contagious to humans. The most deadly
pandemic in modern history was the 1918 influenza, also known as the Spanish
flu (although it did not originate in Spain). The 1918 virus spread rapidly and
killed tens of millions of people worldwide. Mortality was especially high in
healthy young adults. Although the 1918 virus was a human influenza virus it, had
many genes that likely came from a strain of bird flu. One reason that health
officials carefully watch for and try to limit human contact with birds that
develop avian flu is to avoid chances for a new strain to arise that may prefer
to develop in human tissue.
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.
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.
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.
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).
Travelers should prepare for their trip by visiting their physician to get the proper vaccinations and obtain the necessary medication if they have a medical condition or chronic disease. Diseases that travelers may pick up from contaminated water or food, insect or animal bites, or from other people include malaria, meningococcal meningitis, yellow fever, hepatitis A, typhoid fever, polio, and cholera.
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