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Query: UMLS:C0023241 (Legionella)
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Medical science has made tremendous strides in overcoming infectious diseases in the 20th century. Despite this, several epidemics of previously unrecognized diseases have occurred during the last 15 years. These diseases include Lyme disease, Legionnaires' disease, toxic shock syndrome, and AIDS. Examination of past epidemics, including the plague of Athens, the black death, syphilis, and influenza, suggests that the sudden occurrence of diseases that were previously unrecognized is not unusual. Analysis of the new infectious disease indicates that while all four appeared suddenly, isolated cases of the disease occurred before the actual epidemic. Further, all four new diseases were found to be due to agents or toxins that were not previously recognized. Epidemics due to new infectious diseases may arise by several mechanisms, including mutation of the pathogen to a virulent form and introduction of an infectious agent into a nonimmune population. Environmental and behavioral factors may play an important role, as illustrated by toxic shock syndrome, Legionnaires' disease, and AIDS. On the other hand, epidemic diseases tend to abate over time because of changes in the infecting pathogen and in the host. Hence, epidemics can be seen as cycles; new diseases will arise periodically, occasionally with a devastating outcome. With time the effects of these diseases on the population will ameliorate. The cycle will begin again when a new disease emerges.
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PMID:Plagues--what's past is present: thoughts on the origin and history of new infectious diseases. 192 88

Emerging diseases are those which have shown an increased in humans over the last 20 years. Re-emerging diseases are those which have reappeared after a period of significant decrease in incidence. The etiological agents of these diseases in the Western Hemisphere are viruses (HIV, dengue, oroupuche, sabia, guanarito, or hanta), bacteria (Vibrio cholera, Borrellia burgdorferi, Legionella pneumofila, Eseherichia coli 0157:H7, or other bacteria with a new pattern of antibiotic resistance), or parasites (Cryptosporidia, Cyclosporidia or drug resistant Plasmodium falciparum). Due to the widespread geographical distribution of these infectious diseases in the Americas, and an increasing number of travellers (more than 87 million persons within the region in 1997), there are many opportunities to contract an infection when travelling in developed or undeveloped countries. The infection may present with symptoms during the trip, or following the traveler s return to his or her place of origin. However, too often practicing physicians do not inquire about the travel history of their patients and, when they do, they often lack the information about diseases relevant to travelers. From the regional perspective, the emerging or reemerging agents that pose a higher risk to tourists or travelers are: 1) those that cause enteric infections; 2) sexually transmitted diseases; and 3) vector-borne diseases, including those present in ecotourism areas. Emerging and re-emerging diseases that physicians may encounter in their clinical practice while caring for travelers returning from different countries of the Western Hemisphere are briefly described (Lyme disease, legionellosis, dengue, yellow fever, P. falciparum malaria, cyclosporidiosis and cryptosporidiosis). This report attempts to draw attention to the fact that new clinical and etiological entities are present in several geographical areas of the Americas; to place each of these entities into an epidemiological context; and to end the misconception that only travel to poor countries carries a risk of acquiring an infection. By knowing which infectious agents occur in each area and the incubation period of each disease, the treating physician can often treat patients successfully. Health care professionals must be aware of the organisms circulating in the region so that they have them in mind during their clinical practice.
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PMID:Tourism and Emerging and Re-emerging Infectious Diseases in the Americas: What Physicians Must Remember for Patient Diagnosis and Care. 1109 91

In the first half of the 20th century, improved living conditions, preventive measures, vaccines and antibiotics led to a marked reduction in morbidity and mortality from infectious diseases. It was predicted that the conquest of all infectious diseases was imminent. However, 50 years later, in 1999, they were still the major cause of disease worldwide, and caused nearly one third of all deaths (a total of 55.9 million). The eradication of smallpox in the 1970s and the approaching eradication of poliomyelitis represent major achievements. The prevalence of measles, pertussis and tetanus neonatorum is also markedly reduced, but still 1.5 million children in developing countries die each year because of lack of vaccines. Malaria and tuberculosis are re-emerging. Tuberculosis and HIV/AIDS are the diseases with known aetiology that cause most deaths, altogether 5 million each year. Respiratory and gastrointestinal infections cause 6.5 million deaths annually. Infections in the immunocompromised host have become a "trade mark" of today's advanced medicine. Almost every year, new diseases related to new micro-organisms are described; over the last 30 years, approximately 40 new diseases/micro-organisms have been diagnosed. Among the best known are HIV/AIDS, peptic ulcer caused by Helicobacter pylori, Legionnaires' disease, borreliosis (Lyme disease), hepatitis C, gastroenteritis caused by rotavirus, and Ebola haemorrhagic fever. Antimicrobial resistance development of micro-organisms has become one of the major health problems worldwide; a number of preventive measures are being introduced.
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PMID:[Microorganisms strike back--infectious diseases during the last 50 years]. 1180 14

The Department of Health and Human Services (DHHS) has played a critical lead role over the past two years in fostering activities associated with the medical and public health response to bioterrorism. Based on a charge from Secretary Donna Shalala in 1998, the Centers for Disease Control and Prevention (CDC) is leading public health efforts to strengthen the nation's capacity to detect and respond to a bioterrorist event. As a result of our efforts, federal, state, and local communities are improving their public health capacities to respond to these types of emergencies. For many of us in public health, developing plans and capacities to respond to acts of bioterrorism is an extension of our long-standing roles and responsibilities. These are stated in the CDC Mission Statement: to promote health and quality of life by preventing and controlling disease, injury, and disability, and the Bioterrorism Mission: to lead the public health effort in enhancing readiness to detect and respond to bioterrorism. CDC's infectious diseases control efforts are summarized below: --Initially formed to address malaria control in 1946; --Established the epidemic Intelligence Service in 1951; --Participated in global smallpox eradication and other immunization programs; --Estimated 800-1,000 + field investigations/year since late 1990s; --New diseases: Legionnaire's Disease, toxic shock syndrome, Lyme disease, HIV, hantavirus pulmonary syndrome, West Nile, etc. -- Today: focus on emerging infections and bioterrorism. Over the past 50 years, CDC has seen a decline in the incidence of some infectious diseases and an increase in some, whereas others continue to present on a more unpredictable basis (i.e., hantavirus). Outbreak identification, investigation, and control have been an integral part of what we do for more than 50 years. We estimate that 800 to 1,000 field investigations have occurred every year since the late 1990s. Today, however, we have a new focus on emerging infectious diseases and bioterrorism.
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PMID:CDC's strategic plan for bioterrorism preparedness and response. 1188 Jun 62

A variety of newly discovered pathogens and new forms of older infectious agents threaten to reemerge. Typical symptoms of acute infection are fever, headache, malaise, vomiting, and diarrhea. Some of the better-known emerging viral infections include dengue, filoviruses (Ebola, Marburg), hantaviruses, hepatitis B, hepatitis C, HIV, influenza, lassa fever, measles, rift valley fever, rotavirus, and yellow fever. Emerging bacterial infections include cholera, Escherichia coli 0157:H7, legionnaires disease (Legionella), lyme disease, streptococcus infections (group A), tuberculosis, and typhoid. Emerging parasitic infections include cryptosporidium and other waterborne pathogens and malaria. The causes of many diseases are still shrouded in mystery; thus, treatments and cures for them are as yet unknown.
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PMID:The threat of emerging infections. 1234 57

In July 1976, the American Legion held a conference at the Bellevue Stratford Hotel in Philadelphia, PA, to celebrate the nation's bicentennial. This convention resulted in transmission of a gram-negative bacterium to over 200 attendees, who developed a respiratory illness; 34 deaths were attributed to the infections. An investigation of the illness revealed a bacterium that had not been documented before. The disease became known as Legionnaires' disease, and the etiological agent was subsequently named Legionella pneumophila. This is the story of Legionella, with special emphasis on its ecological niche, the diagnosis of human infection, and its isolation from the environment. There are only a handful of diseases that debuted in the 20th or 21st century. They include Legionnaires' disease (the subject of this review), Lyme disease, AIDS, severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), and West Nile virus.
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PMID:Legionella: a Fascinating Bacterium Uncovered in the Twentieth Century. 3228 85