Presentation on theme: "Super Pathogens WHAT ARE THEY AND HOW TO AVOID THEM Evan Collette Ashley Tourigney."— Presentation transcript:
Super Pathogens WHAT ARE THEY AND HOW TO AVOID THEM Evan Collette Ashley Tourigney
Community Based Disease As members of any emergency response team it important for us to be aware of new strains of communicable disease which we may be exposed to and universally approved prevention techniques used to safeguard health care workers.
VRE Vancomycin-resistant enterococci Enterococci is a bacteria. It is present in intestines and female genital tract normally and can live without causing harm. When the bacteria seeds elsewhere it will cause infections including urinary tract, blood, and wound infections.
Vancomycin Vancomycin in an antibiotic used to treat the infections caused by enterococci. In some cases the bacteria has become resistant to this antibiotic. They call this resistant bacteria VRE (vancomycin-resistant enterococci).
How is VRE spread? VRE is usually passed to others by direct contact with stool, urine or blood containing VRE. It can also be spread indirectly via the hands or on contaminated environmental surfaces. VRE usually is not spread through casual contact such as touching or hugging. VRE is not spread through the air by coughing or sneezing.
People at increased Risk Individuals who have been treated in the past with vancomycin and combinations of other antibiotics. People in hospitals, esp. on antibiotics for long durations. People with weak immune systems or who have had surgical procedures. People with indwelling percutaneous medical devices and catheters.
Treatment Most VRE infections can be treated with antibiotics other than vancomycin. The treatment of VRE is determined by laboratory testing to determine which antibiotics are effective. People who are colonized (bacteria are present, but have no symptoms of an infection) with VRE do not usually need treatment.
Prevention Always wash your hands thoroughly after using the bathroom and before preparing food. Wash with soap and water (particularly when visibly soiled) or clean with alcohol-based hand cleaner. Use a household disinfectant or a mixture of one-fourth cup bleach and one quart of water to clean those areas and surfaces that are touched frequently. Wear gloves if you may come in contact with body fluids that may contain VRE, such as stool. Always wash your hands after removing gloves.
Hepatitis Hepatitis means an inflammation of the liver. There are 5 viruses that can cause hepatitis. Some of the viruses can change over time making it difficult for the body to fight.
Hepatitis Hepatitis AHepatitis A: is a liver disease caused by the hepatitis A virus (HAV). Hepatitis A can affect anyone. In the United States, hepatitis A can occur in situations ranging from isolated cases of disease to widespread epidemics.
Hepatitis Hepatitis BHepatitis B: is a serious disease caused by a virus that attacks the liver. The virus, which is called hepatitis B virus (HBV), can cause lifelong infection, cirrhosis (scarring) of the liver, liver cancer, liver failure, and death.
Hepatitis Hepatitis CHepatitis C: is a liver disease caused by the hepatitis C virus (HCV), which is found in the blood of persons who have the disease. HCV is spread by contact with the blood of an infected person.
Hepatitis Hepatitis DHepatitis D: is a liver disease caused by the hepatitis D virus (HDV), a defective virus that needs the hepatitis B virus to exist. Hepatitis D virus (HDV) is found in the blood of persons infected with the virus.
Hepatitis Hepatitis EHepatitis E: is a liver disease caused by the hepatitis E virus (HEV) transmitted in much the same way as hepatitis A virus. Hepatitis E, however, does not occur often in the United States.
Acute Hepatitis – Clinical Symptoms Asymptomatic > Symptomatic > Fulminant Liver Failure > Death Symptoms (if present) are the same, regardless of cause (e.g., A, B, C, other viruses, toxins) Nausea, vomiting Abdominal pain Loss of appetite Fever Diarrhea Light (clay) colored stools Dark urine Jaundice (yellowing of eyes, skin)
NUMBER OF YEARS REPORTED INCIDENCE OF HEPATITIS A EXCEEDED 10 CASES PER 100,000, BY COUNTY,
Hepatitis A Transmitted through close personal contact (e.g., household contact, sex contact, child day-care centers), contaminated food, water (e.g., infected food handlers), blood exposure (rare) (e.g., injection drug use, rarely by transfusion) It occurs most often in children and young adults, esp. in autumn and winter. Symptoms include: jaundice, malaise, nausea, diarrhea, abdominal pain, and lack of appetite for a period of 2 days-3 weeks.
Preventing Hepatitis A Vaccine: 97%-100% of children, adolescents, and adults have protective levels of antibody within 1 month of receiving first dose; essentially 100% have protective levels after second dose. Serum titers for up eight years. Hygiene (e.g., hand washing) Sanitation (e.g., clean water sources) Hepatitis A vaccine (pre-exposure) Immune globulin (pre- and post-exposure)
Hepatitis B hepatitis B virus hepatitis B virus hepatitis B virus hepatitis B virus hepatitis B virus hepatitis B virus hepatitis B virus hepatitis B virus
Hepatitis B Hepatitis B is a serious disease caused by a virus that attacks the liver. The virus, which is called hepatitis B virus (HBV), can cause lifelong infection, cirrhosis (scarring) of the liver, liver cancer, liver failure, and death. About 30% of persons have no signs or symptoms. Signs and symptoms are less common in children than adults. It occurs in people of all ages with about the same incidence throughout the year.
Hepatitis B Occurs when blood from an infected person enters the body of a person who is not infected. HBV is spread through having sex with an infected person without using a condom, by sharing needles, needlesticks or sharps exposures on the job, or from an infected mother to her baby during birth. Persons at risk for HBV infection might also be at risk for infection with hepatitis C virus (HCV) or HIV.
Hepatitis B The hepatitis B virus takes about 2 months to show up in your blood. It may stay in your blood for months or years. Acute Hepatitis B: 9 out of every 10 adults will get rid of the virus from their bodies after a few months. The symptoms will go away on their own within a few weeks there is no treatment other than alleviating the symptoms. Chronic Hepatitis B: 1 out of every 10 adults will never get rid of the virus from their bodies. They are called carriers. After having the virus the person has immunity to it and for others a vaccine is available.
Hepatitis C Hepatitis C can lead to cirrhosis or liver cancer, it is a leading reason for liver transplants. It is transmitted person to person by blood or body fluids. Although the disease usually is mild or seemingly inapparent, the infection can be severe in compromised individuals and will become chronic in about 80% of those infected.
Hepatitis C There is no cure or vaccine for Hepatitis C. No immunity is developed following an infection. Some medications are currently used to help control the disease.
Staphylococcus aureus “staph” Staphylococcal InfectionsStaphylococcal Infections -Staph is short for Staphylococcus, a type of bacteria. There are over 30 types, but Staphylococcus aureus causes most staph infections, including Skin infections, Pneumonia, Food poisoning, and Toxic shock.
Staphylococcus aureus “staph” This bacteria is carried on the skin or in the nose of healthy people. Not everyone gets infections from “staph” bacteria when it is present on their body. Some people do get skin infections such as pimples and boils, they are treatable. In other cases the infection can be serious causing wound infections, bloodstream infections, and pneumonia.
Methicillin-resistant Staphylococcus aureus (MRSA) MRSA is a type ot “staph” infection that is resistant to antibiotics called beta-lactams. β-lactam antibiotics are a broad class of antibiotics that include penicillin derivatives, cephalosporins, monobactams (imipenem), carbapenems (aztreonam), and β-lactamase inhibitorsantibioticspenicillincephalosporins monobactamscarbapenemsβ-lactamase inhibitors Of 25-30% of people colonized with staph about 1% is colonized with MRSA.
Methicillin-resistant Staphylococcus aureus (MRSA) Methicillin-resistant Staphylococcus aureus (MRSA) are identified as nosocomial pathogens throughout the world. People who get MRSA are frequently in hospitals and healthcare facilities, with weakened immune systems. Recently, however, cases of MRSA have been documented in healthy community-dwelling persons without established risk factors for MRSA acquisition.
How do you get MRSA? You can get MRSA by having physical contact with someone who is infected with it or carrying it on their body. Another way is to touch an object that has MRSA on it, ex: a door knob. Normal skin of people does not allow the infection to develop, however an abrasion or cut on the skin will allow it to.
MRSA Signs and Symptoms Infection of the skin starting with small red bumps in the skin Pus-filled infections of hair follicles Collections of pus in under the skin Infection of eyelid gland Infections of the skin with openings Pus filled blisters MRSA can spread to internal organs as well and can cause chills, low BP, rash, joint pains, severe headaches and shortness of breath.
Treatments for MRSA Most MRSA can be treated by certain antibiotics like vancomycin and linezolid. The entire dosage of antibiotic needs to be taken to “cure” the infection.
Avoid getting MRSA by… Cover any skin breaks with antiseptic cream and a Band-Aid Use excellent hygiene practices Wash clothes in contact with MRSA patients or carriers Use disposable items when treating MRSA patients Use antiseptic solutions and wipes to clean both hands and surfaces that may contact MRSA
Clostridium difficile (C.difficle) This is a bacterium that causes diarrhea and more serious intestinal conditions. There is an increased risk when on antibiotics, because the antibiotic alters the bodies levels of good bacteria in the intestines. Clindamycin is the antibiotic most frequently associated with C. difficile infections followed by ampicillin and cephalosporins.
Clostridium difficile The elderly and people in the hospital are at greater risk, healthy people are not usually affected. Once C. difficile has established its self in an environment it is difficult to remove. Symptoms of this colitis include abdominal cramps, diarrhea, fever, electrolyte imbalance, and potential perforation of the colon in severe infections.
Modes of Transmission Contact Transmission Vector Transmission Vehicle Transmission
Contact Transmission Direct contact transmission requires body contact between individuals. In the health care worker these can be spread through unhygienic practice. An example would be direct fecal-oral transmission transfers fecal pathogens to mouth via unwashed hands. Staphylococcal infections, warts and STD’s are of major concern.
Contact Transmission Indirect contact transmission occurs through non-living objects that can harbor and transmit an infectious agent. Examples include soiled handkerchiefs, dishes, eating utensils, doorknobs, bar soap and money. Tetanus, common cold, enterovirus and ringworm are commonly transmitted this way.
Contact Transmission Droplet transmission occurs when a person speaks, coughs, or sneezes near others. The area of greatest exposure is within one meter of the infected person. Common cold, influenza, measles, pneumonia, and whooping cough are commonly spread this way.
Vehicle Transmission Waterborne pathogens thrive in water contaminated by untreated sewage. Cholera, shigellosis and Campylobacter infections can be transmitted this way. Of major concern would be indirect fecal transmission when pathogens of feces of one organism affect another organism.
Vehicle Transmission Airborne microorganisms including dust particles can be transients from soil, water, plants or animals. Chickenpox, tuberculosis, measles and influenza are commonly transmitted this way. Pathogens are said to be airborne if they travel more than one meter this way.
Vehicle Transmission Foodborne transmission has been a mode of spreading hepatitis A, staphylococcal food poisoning, salmonellosis, typhoid fever and botulinum toxin. They are usually the result of poorly refrigerated, incompletely cooked or poorly processed foods. They manifest themselves through gastrointestinal symptoms.
Vector Transmission Mechanical transmission (on insect bodies such as flies) spreading diseases. These include E. coli diarrhea, salmonellosis and trachoma. Pathogens are spread from insects to food which is then ingested by humans.
Best Defense USE GLOVES AND DON’T TOUCH BODY FLUIDS UNPROTECTED
Best Defense WASH HANDS OFTEN
Best Defense Use of masks are recommended when exposure to infected individuals is identified but it is important to note that even surgical masks will not prevent the spread of all droplets.
Best Defense Masks are very useful in impeding the spread of airborne disease but of even greater impact is the cleaning of areas of exposure with wet mops and damp cloths.
Best Defense In the event of an emergency, drinking of bottled water would be advised.
Best Defense In an emergency situation when food goods are being supplied dried packaged foods are the best safe source of nutrition.
Best Defense Keeping these insects and other potential vectors away from the food supply.
Bioterrorism the deliberate release of viruses, bacteria, or other germs (agents) used to cause illness or death in people, animals, or plants
Bioterrorism Agent Categories Category A Pose the highest risk to the public and national security because: They can be easily spread or transmitted from person to person They result in high death rates and have the potential for major public health impact They might cause public panic and social disruption They require special action for public health preparedness
Category B These agents are the second highest priority because: They are moderately easy to spread They result in moderate illness rates and low death rates They require specific enhancements of CDC's laboratory capacity and enhanced disease monitoring.
Category C Include emerging pathogens that could be engineered for mass spread in the future because: They are easily available They are easily produced and spread They have potential for high morbidity and mortality rates and major health impact.
Anthrax Bacillus Caused by the spore-forming bacterium, Bacillus anthracis Zoonotic disease in herbivores (e.g., sheep, goats, cattle) follows ingestion of spores in soil Human infection typically acquired through contact with anthrax-infected animals or animal products or atypically through intentional exposure Three clinical forms Cutaneous Inhalational Gastrointestinal
Anthrax: Current Issues in the U.S. Anthrax remains an endemic public health threat through annual epizootics. B. anthracisis one of the most important pathogens on the list of bioterrorism threats Aerosolized stable spore form Human LD50 8,000 to 40,000 spores, or one deep breath at site of release
Anthrax: Cutaneous Begins as a papule, progresses through a vesicular stage to a depressed black necrotic ulcer (eschar) Edema, redness, and/or necrosis without ulceration may occur Form most commonly encountered in naturally occurring cases Incubation period: 1–12 days Case-fatality: Without antibiotic treatment—20% With antibiotic treatment—1%
Left image: forearm lesion on Day 7—vesiculation and ulceration of initial macular or papular anthrax skin lesion. Right image: eschar of the neck on Day 15, typical of the last day of lesion. From Binford CH, Connor DH, eds. pathology of tropical and extraordinary diseases. Vol 1. Washington DC: AFIP:1976:119. AFIP negative NEJM 1999:341: Anthrax Cutaneous
Anthrax: Inhalational A brief prodrome resembling a “viral- like”illness, characterized by myalgia, fatigue, fever, with or without respiratory symptoms, followed by hypoxia and dyspnea, often with radiographic evidence of mediastinal widening. Meningitis in 50% of patients Rhinorrhea (rare)
Anthrax: Inhalational Extremely rare in United States (20 reported cases in last century) Incubation period: 1–7 days (possibly ranging up to 42 days) Case fatality: Without antibiotic treatment—97% With antibiotic treatment—75%
Mediastinal widening and pleural effusion on Chest X-Ray in inhalation anthrax Anthrax: Inhalational
Anthrax: Gastrointestinal Abdominal distress, usually accompanied by bloody vomiting or diarrhea, followed by fever and signs of septicemia Gastrointestinal illness sometimes seen as oropharyngeal ulcerations with cervical adenopathy and fever Develops after ingestion of contaminated, poorly cooked meat. Incubation period: 1–7 days Case-fatality: 25–60% (role of early antibiotic treatment is undefined)
Disinfecting Effective sporicidal solutions Commercially-available bleach, 0.5% hypochlorite (1 part household bleach to 9 parts water) Rinse off concentrated bleach to avoid caustic effects Approved sporicidal agents Incinerate infected material, and suspect material.
Brucellosis Zoonotic infection transmitted from animals to humans by ingestion of infected food products, direct contact with an infected animal, or inhalation of aerosols. This last method of transmission is remarkably efficient given the relatively low concentration of organisms (as few as bacteria) needed to establish infection in humans and has brought renewed attention to this old disease. Its relatively long and variable incubation period (1-8 wk), as well as the fact that many infections are asymptomatic, has made it a less desirable agent for weaponization.
But… Because of the predilection to affect joints and the vague symptoms and chronic nature of the disease, symptoms can result in relatively long- term disability. The potential for long-lasting infection that can disable workers in either military or civilian circles makes Brucella species an appealing choice for a biological weapon. Mortality from brucellosis is rare and is usually secondary to endocarditis (which occurs in approximately 2% of patients). Nearly all patients respond to appropriate antibiotic therapy, with fewer than 10% relapsing.
Treatment Given the nonspecific patient complaints, a diagnosis of brucellosis is unlikely in the ED. With an appropriate history, an astute clinician may suspect it. Respiratory isolation/masks usually is not necessary unless close contact with the respiratory tract for intubation, suctioning, or other maneuvers that may expose the caregiver to a large concentration of aerosolized particles. The appropriate antibiotic therapy for brucellosis is combination therapy with doxycycline and rifampin or streptomycin. There is some evidence of growing resistance to rifampin in some areas, though ciprofloxacin and aminoglycosides maintain good coverage.
Botulism Botulism is a muscle-paralyzing disease caused by a toxin made by a bacterium called Clostridium botulinum.
Botulism There are three main kinds of botulism: Foodborne botulism occurs when a person ingests pre- formed toxin that leads to illness within a few hours to days. Foodborne botulism is a public health emergency because the contaminated food may still be available to other persons besides the patient. Infant botulism occurs in a small number of susceptible infants each year who harbor C. botulinum in their intestinal tract. Wound botulism occurs when wounds are infected with C. botulinum that secretes the toxin.
Botulism Treatment An antitoxin, available in the U.S. from the Centers for Disease Control and Prevention, stops progression of the disease and can prevent onset of disease following exposure. Vaccine No vaccine is available for the general public. An investigational vaccine is available for the military and lab workers
Botulism Symptoms nausea and vomiting (occurs in natural cases when bacteria are ingested; may not appear if purified toxin is spread on food) difficulty speaking, seeing, and/or swallowing drooping eyelids muscle weakness starting in the trunk and moving to the limbs muscle paralysis and difficulty breathing
Plague Plague is an infectious disease of animals and humans caused by a bacterium named Yersinia pestis. Yersinia pestis is easily destroyed by sunlight and drying. Even so, when released into air, the bacterium will survive for up to one hour, depending on conditions.
Plague Pneumonic plague can be transmitted from person to person; bubonic plague cannot. Pneumonic plague affects the lungs and is transmitted when a person breathes in Y. pestis particles in the air. Bubonic plague is transmitted through the bite of an infected flea or exposure to infected material through a break in the skin. Symptoms include swollen, tender lymph glands called buboes. Buboes are not present in pneumonic plague.
Plague When bubonic plague is left untreated, plague bacteria invade the bloodstream. Infection of the lungs with the plague bacterium causes the pneumonic form of plague, a severe respiratory illness. The infected person may experience high fever, chills, cough, and breathing difficulty and may expel bloody sputum. If plague patients are not given specific antibiotic therapy, the disease can progress rapidly to death. About 14% (1 in 7) of all plague cases in the United States are fatal.
Plague The typical sign of the most common form of human plague is a swollen and very tender lymph gland, accompanied by pain. The swollen gland is called a "bubo." Bubonic plague should be suspected when a person develops a swollen gland, fever, chills, headache, and extreme exhaustion, and has a history of possible exposure to infected rodents, rabbits, or fleas. A person usually becomes ill with bubonic plague 2 to 6 days after being infected.
Plague To prevent a high risk of death, antibiotics should be given within 24 hours of the first symptoms. Several types of antibiotics are effective for curing the disease and for preventing it. Available oral medications are a tetracycline (such as doxycycline) or a fluoroquinolone (such as ciprofloxacin). For injection or intravenous use, streptomycin or gentamicin antibiotics are used. Early in the response to a bioterrorism attack, these drugs would be tested to determine which is most effective against the particular weapon that was used.
Smallpox The only known reservoir for the virus is humans; there are no known animal or insect reservoirs or vectors. The most frequent mode of transmission is person-to-person spread via direct droplets onto the nasal, oral, or pharyngeal mucosal membranes or in the alveoli of the lungs from close, face-to- face contact with an infectious individual. Indirect spread (not requiring face-to-face contact with an infectious individual) via fine-particle aerosols or fomites has been reported but is less common.
Smallpox Symptoms usually begin within 12 to 14 days (range 7 to 17) following the exposure. The initial symptoms usually consist of high fever, malaise, fatigue, and severe headache and backache followed by the appearance of a maculopapular rash (eruptive stage) that progresses to papules (1 to 2 days after appearance of rash), vesicles (~ 4 th to 5 th day), pustules (by ~ 7 th day), and finally scab lesions (~ 14 th day). The rash generally appears first on the oral mucosa, face, and forearms and then spreads to the trunk and legs. Lesions are also seen on the palms of the hands and soles of the feet.
These are smallpox lesions on the skin of the trunk. This photograph was taken in Bangladesh in 1973 Smallpox
Smallpox vaccine, a live-virus vaccine made from vaccinia virus, is highly effective at inducing immunity against smallpox prior to exposure. If administered within 3 days after exposure to smallpox virus, it may prevent disease, or decrease the severity of disease and risk of death. Smallpox vaccine production ceased in the early 1980s and current supplies of smallpox vaccine are limited.
Smallpox No cure for smallpox exists. Historically, variola major is fatal in about 30 percent of people who contract it. Almost no one survives the hemorrhagic and malignant forms of the disease. People who recover from smallpox usually have severe scars, especially on the face, arms and legs. In many cases, smallpox may lead to blindness.
Tularemia Tularemia_Bacteria. health.utah.gov
Tularemia Francisella tularensis is very infectious. A small number (10-50 or so organisms) can cause disease. If F. tularensis were used as a weapon, the bacteria would likely be made airborne for exposure by inhalation. People who inhale an infectious aerosol would generally experience severe respiratory illness, including life-threatening pneumonia and systemic infection, if they are not treated. The bacteria that cause tularemia occur widely in nature and could be isolated and grown in quantity in a laboratory, although manufacturing an effective aerosol weapon would require considerable sophistication.
Tularemia People can get tularemia many different ways: being bitten by an infected tick, deerfly or other insect handling infected animal carcasses eating or drinking contaminated food or water breathing in the bacteria, F. tularensis Tularemia is not known to be spread from person to person. People who have tularemia do not need to be isolated. People who have been exposed to the tularemia bacteria should be treated as soon as possible. The disease can be fatal if it is not treated with the right antibiotics.
Tularemia Symptoms usually appear 3 to 5 days after exposure to the bacteria, but can take as long as 14 days. Symptoms of tularemia could include: sudden fever chills headaches diarrhea muscle aches joint pain dry cough progressive weakness
Tularemia People can also catch pneumonia and develop chest pain, bloody sputum and can have trouble breathing and even sometimes stop breathing. Other symptoms of tularemia depend on how a person was exposed to the tularemia bacteria. These symptoms can include ulcers on the skin or mouth, swollen and painful lymph glands, swollen and painful eyes, and a sore throat.
Viral Hemorrhagic Fevers Viral hemorrhagic fevers (VHFs) refer to a group of illnesses that are caused by several distinct families of viruses. In general, the term "viral hemorrhagic fever" is used to describe a severe multisystem syndrome (multisystem in that multiple organ systems in the body are affected).
Viral Hemorrhagic Fevers VHFs are caused by viruses of four distinct families: Arenaviruses, filoviruses, bunyaviruses, and flaviviruses. Each of these families share a number of features : They are all RNA viruses, and all are covered, or enveloped, in a fatty (lipid) coating. Their survival is dependent on an animal or insect host. The viruses are geographically restricted to the areas where their host species live. Humans are not the natural reservoir for any of these viruses. Human cases or outbreaks of hemorrhagic fevers caused by these viruses occur sporadically and irregularly. With a few noteworthy exceptions, there is no cure or established drug treatment for VHFs.
Viral Hemorrhagic Fevers Specific signs and symptoms vary by the type of VHF, but initial signs and symptoms often include marked fever, fatigue, dizziness, muscle aches, loss of strength, and exhaustion. Patients with severe cases of VHF often show signs of bleeding under the skin, in internal organs, or from body orifices like the mouth, eyes, or ears. However, although they may bleed from many sites around the body, patients rarely die because of blood loss. Severely ill patient cases may also show shock, nervous system malfunction, coma, delirium, and seizures. Some types of VHF are associated with renal (kidney) failure.
Viral Hemorrhagic Fevers Treatment is supportive care. Best measures are preventive by controlling the rodent population and clearing areas of rodent urine and droppings. Presently there is one hemorrhagic fever virus that has been identified as a potential bioterrorism agent. These viruses are of concern because it takes a very small amount to infect.
Resources Division of Viral Hepatitis Centers for Disease Control and Prevention National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention Centers for Disease Control and Prevention, 1600 Clifton Rd, Atlanta, GA 30333, Public Inquiries: (404) / (800) Emergency Preparedness & Response Centers for Disease Control and Prevention, 1600 Clifton Rd, Atlanta, GA 30333, USA CDC Contact Center: 800-CDC-INFO ( ) (TTY) Director's Emergency Operations Center (DEOC): CBRNE- Brucellosis Author:Author: Gerald E Maloney Jr, DO, FAAEM, Senior Instructor, Department Emergency Medicine, Case Western Reserve University School of Medicine; Consulting Staff, Department of Emergency Medicine and Medical Toxicology, Flight Physician, Metro Life Flight, MetroHealth Medical Center. Retrieved from eMedicine March 21, 2008http://www.emedicine.com/emerg/topic883.htm