Pandemic
From Wikipedia, the free encyclopedia
Please improve this article if you can. (December 2007)
A pandemic (from Greek παν pan all + δήμος demos people) is an epidemic of infectious disease that spreads through human populations across a large region; for instance a continent, or even worldwide.
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[edit] Definition
According to the World Health Organization (WHO), a pandemic can start when three conditions have been met:
A disease or condition is not a pandemic merely because it is widespread or kills many people; it must also be infectious. For instance, cancer is responsible for many deaths but is not considered a pandemic, because the disease is not infectious or contagious (although certain cases of some types of cancer might be).
[edit] WHO pandemic influenza phases
The World Health Organization Global Influenza Preparedness Plan defines the stages of pandemic influenza, outlines the role of the WHO and makes recommendations for national measures before and during a pandemic. The phases are:
Interpandemic period:
Pandemic alert period:
Pandemic period:
[edit] Pandemics and notable epidemics through history
There have been a number of significant pandemics recorded in human history, generally zoonoses which came about with domestication of animals — such as influenza and tuberculosis. There have been a number of particularly significant epidemics that deserve mention above the "mere" destruction of cities:
There are also a number of unknown diseases that were extremely serious but have now vanished, so the etiology of these diseases cannot be established. The cause of English Sweat in 16th-century England, which struck people down in an instant and was more greatly feared than even the bubonic plague, is still unknown.
[edit] Concern about possible future pandemics
[edit] Ebola virus and other quickly lethal diseases
Lassa fever, Rift Valley fever, Marburg virus, Ebola virus and Bolivian hemorrhagic fever are highly contagious and deadly diseases, with the theoretical potential to become pandemics. Their ability to spread efficiently enough to cause a pandemic is limited, however, as transmission of these viruses requires close contact with the infected vector. Furthermore, the short time between a vector becoming infectious and the onset of symptoms allows medical professionals to quickly quarantine vectors, and prevent them from carrying the pathogen elsewhere. Genetic mutations could occur, which could elevate their potential for causing widespread harm; thus close observation by contagious disease specialists is merited.
[edit] Antibiotic resistance
Antibiotic-resistant microorganisms, sometimes referred to as "superbugs", may contribute to the re-emergence of diseases which are currently well-controlled. For example, cases of tuberculosis that are resistant to traditionally effective treatments remain a cause of great concern to health professionals. The World Health Organization (WHO) reports that approximately 50 million people worldwide are infected with multiple-drug resistant tuberculosis (MDR TB), with 79 percent of those cases resistant to three or more antibiotics. In 2005, 124 cases of MDR TB were reported in the United States. Extensively drug-resistant tuberculosis (XDR TB) was identified in Africa in 2006, and subsequently discovered to exist in 17 countries, including the United States.
In the past 20 years, common bacteria including Staphylococcus aureus, Serratia marcescens and Enterococcus, have developed resistance to various antibiotics such as vancomycin, as well as whole classes of antibiotics, such as the aminoglycosides and cephalosporins. Antibiotic-resistant organisms have become an important cause of healthcare-associated (nosocomial) infections (HAI). In addition, infections caused by community-acquired strains of methicillin-resistant Staphylococcus aureus (MRSA) in otherwise healthy individuals, have become more frequent in recent years.
[edit] HIV infection
HIV — the virus that causes AIDS — is of pandemic proportions, with infection rates as high as 25% in southern and eastern Africa. Effective education about safer sexual practices and bloodborne infection precautions training have helped to slow down infection rates in several African countries sponsoring national education programs. Infection rates are rising again in Asia and the Americas. See AIDS pandemic.
[edit] SARS
In 2003, there were concerns that SARS, a new, highly contagious form of atypical pneumonia caused by a coronavirus dubbed SARS-CoV, might become pandemic. Rapid action by national and international health authorities such as the World Health Organization helped slow transmission, and eventually broke the chain of transmission, ending the localized epidemics before they could become a pandemic. The disease has not been eradicated, however, and could re-emerge unexpectedly, warranting monitoring and case reporting of suspicious cases of atypical pneumonia.
[edit] Influenza
Wild aquatic birds are the natural hosts for a range of influenza A viruses. Occasionally, viruses are transmitted from these species to other species, and may then cause outbreaks in domestic poultry or (rarely) give rise to a human pandemic. [10][11]
[edit] H5N1
In February 2004, avian influenza virus was detected in birds in Vietnam, increasing fears of the emergence of new variant strains. It is feared that if the avian influenza virus combines with a human influenza virus (in a bird or a human), the new subtype created could be both highly contagious and highly lethal in humans. Such a subtype could cause a global influenza pandemic, similar to the Spanish Flu, or the lower mortality pandemics such as the Asian Flu and the Hong Kong Flu.
From October 2004 to February 2005, some 3,700 test kits of the 1957 Asian Flu virus were accidentally spread around the world from a lab in the US[2].
In May 2005, scientists urgently call nations to prepare for a global influenza pandemic that could strike as much as 20% of the world's population.[citation needed]
In October 2005, cases of the avian flu (the deadly strain H5N1) were identified in Turkey. EU Health Commissioner Markos Kyprianou said: "We have received now confirmation that the virus found in Turkey is an avian flu H5N1 virus. There is a direct relationship with viruses found in Russia, Mongolia and China." Cases of bird flu were also identified shortly thereafter in Romania, and then Greece. Possible cases of the virus have also been found in Croatia, Bulgaria and the United Kingdom [3].
By November 2007, numerous confirmed cases of the H5N1 strain had been identified across Europe [4]. However, by the end of October only 59 people had died as a result of H5N1 which was atypical of previous influenza pandemics.
Despite sensationalizing media reporting, avian flu cannot yet be categorized as a "pandemic", because the virus cannot yet cause sustained and efficient human-to-human transmission. Cases so far are recognized to have been transmitted from bird to human, but as of December 2006 there have been very few (if any) cases of proven human-to-human transmission. Regular influenza viruses establish infection by attaching to receptors in the throat and lungs, but the avian influenza virus can only attach to receptors located deep in the lungs of humans, requiring close, prolonged contact with infected patients, and thus limiting person-to-person transmission. The current WHO phase of pandemic alert is level 3, described as "no or very limited human-to-human transmission", according to the WHO website.
