Transcript MICR 454L
MICR 454L Emerging and Re-Emerging Infectious Diseases Lecture 1: Identifying the Problem Dr. Nancy McQueen & Dr. Edith Porter Overview – the course Course requirements and challenge for the students Quizzes Midterm Research paper presentation and discussions Hot topics presentations Case studies Comprehensive final exam Quote “There will come yet other new and unusual ailments in the course of time. And this disease will pass away, but it will later be borne again, and be seen by our descendents.” Written 450 years ago! Written by Girolamo Frascatoro Written about syphilis The Problem: Emerging and Reemerging Infectious diseases Overview – the problem Identifying the problem Factors responsible for emerging infections World population growth Urbanization Ecological disturbances Technological advances Microbial evolution and adaptation Human behavior and attitudes The problem of emerging infections The problem is a worldwide challenge by microbes whose survival is linked to ours The vast majority of microbes are beneficial The small minority of microbes that produce disease are called pathogens. History of the current problem From the 1950’s through the 1970’s microbial diseases appeared to be on their way out Vaccinations Antibiotics and other antimicrobics Improved world economy and decreased poverty However, from 1980 to 1992 the CDC reported a 22% increase (excluding AIDS) in infectious diseases The problem of emerging infections Emerging infections are defined as those infections whose incidence in humans has increased in the past two decades or will increase in the future. Emerging infections can be defined as In 1996, published data indicated that since 1980 there was a greater than 50% increase in deaths caused by microbes in the United States. New Reemerging Drug resistant infections Emergence is a two step process Introduction of the infectious agent into a new population. The agent may be: Already present Located within another species A variant of an existing pathogen Dissemination of the infectious agent What are some of these emerging infections? Emerging and Re-emerging Infectious Diseases avian Red names are newly emerging infectious diseases; Blue names are re-emerging infectious diseases; Black names are emerging bioterrorism infectious diseases; Names circled in green are RNA viruses Adapted from Morens, D. M., et al. 2004. The Challenge of Emerging and Re-emerging Infectious Diseases. Nature 430: 242-249 Recent outbreaks of infectious diseases Leading causes of death Leading causes of death 6% 9% Infectious diseases 25% 5% Cardiovascular diseases Cancers Injuries 11% Maternal complications 13% Respiratory and Digestive diseases 31% Other Leading causes of death,1998. There were 53.9 million deaths world-wide in 1998. Cancers, cardiovascular, and respiratory and digestive diseases can also be caused by infections. Thus , the percentage of deaths due to infectious diseases may be even higher than shown. (Source: WHO report, 1999.) Leading causes of death in Africa versus the Americas Africa 2002: 10.7 million deaths 2% 5% 2% 7% Infections Cardiovascular 7% Cancers Injuries 4% Maternal and perinatal Respiratory 63% 10% Intentional Other The Americas 2002: 6 million deaths 11% 14% Infectious 4% Cardiovascular 2% Cancers Injuries 7% 32% 4% Maternal and perinatal Respiratory Intentional Diabetes 7% Other 19% Causes of death in the Americas and Africa, 2002, by percentage of cause. There were 10.7 million deaths in Africa, 6.7 million due to infectious diseases. There were 6 million deaths in the Americas, 623,000 due to infectious diseases. Intentional deaths include murder, suicide, and war. Leading infections disease killers Leading infectious disease killers 4 Deaths in millions 3.5 3 2.5 Over age 5 2 Under age 5 1.5 1 0.5 0 Acute respiratory infection AIDS DiarrhealTuberculosis Malaria diseases Measles Leading infectious killers. The graph shows millions of deaths world-wide in 1998 for persons of all ages. Pneumonia and influenza are included in acute respiratory infections. Deaths among HIV-positive individuals with tuberculosis are included under AIDS. (Source: WHO report, 1999. Factors responsible for emerging diseases World population growth – most important Urbanization (changes in demographics) Ecological disturbances Technical advances Air travel Unsafe blood supplies Human behavior and attitudes Deforestation – disturbances to natural habitat Climate changes Natural disasters (drought, flooding) Complacency Migration Societal factors Microbial evolution and adaptation Antimicrobial resistance Evasive strategies World population growth 10 9 8 7 6 5 4 3 2 1 0 19 45 19 55 19 65 19 75 19 85 19 95 20 05 20 15 20 25 20 35 20 45 Population (in billions) World Population Growth Year World population, 1950 to 2050. Projections are based on an estimated annual growth rate of 1.25%. (Source: U.S. Census Bureau, International Dada Base, May 10, 2000. World population growth is central to the issue Increased urbanization Changes in human behavior and activities Technological advances Population growth Increased transmission Ecological disturbances Advances in biology and medicine How does increased population result in an increase of infectious diseases? Increased transmission Population density Person to person transmission is facilitated by population density increases Distribution of the population The elderly are more susceptible to disease and can serve as a source of infection Other potential effects: Greater likelihood of global warming Larger numbers of travelers More frequent wars Increased numbers of refugees and internally displaced persons How does increased population result in an increase of infectious diseases? Increased hunger and malnutrition More crowded living in urban slums Increased numbers of people living in poverty Inadequate potable water supply More large dam construction and irrigation projects Urbanization In the past 50 years, about 25% of the population have left their rural environment for the cities By 2030, more than 65% of the world’s population will live in cities Urbanization Percent of world population living in cities 5 billion 70 60 2.5 billion 50 750 million 40 30 20 240 million 10 0 1900 1950 1995 2030 Year Progressive urbanization of our planet. The different colors for 2030 indicate proportions of urban population that are projected to live in developed countries (20%) and underdeveloped countries (80%) Urbanization The magnitude of the effect of urbanization on infectious diseases depends upon: Economy of the country Public health infrastructure necessary to cope with the increasing population density Urbanization and poverty Drain on natural resources and increased pollution Decreased public Malnutrition health infrastructure and decreased and *Sanitation health services *Rodent increase *Immunization Increased infectious diseases Slums and shanty towns. Poverty is associated with a lack of sanitary facilities, an increase in rodent populations, a lack of safe drinking water, and other circumstances that contribute to infectious diseases Urbanization Emergence of diseases due to urbanization Dengue fever – is caused by a flavivirus Causes Dengue fever and Dengue hemorrhagic fever Is transmitted by Aedes mosquitoes that are unable to fly long distances House–to-house infestation of the mosquito occurs in cramped urban living conditions Disease has moved into the U.S. as the virus can now infect a different species of Aedes mosquito West Nile virus – is also caused by a flavivirus Is also transmitted by a mosquito vector First identified in the U.S. in New York City in 1999. Spread of WNV in the United States Even in developed countries urbanization often leads to poverty and disease Ecological disturbances Deforestation Deforestation. As people move into and/or develop agriculture in areas that were formerly forests, there is increased contact with animals, including insects, that harbor infectious microbes. In search of food, the displaced animals return to neighborhoods that were once their lands, sometimes transmitting new diseases. Ecological disturbances Deforestation Eastern U.S. Lyme, Connecticut in 1970’s Raccoons foraging for food rabies (zoonotic disease - transmitted from animal to human) Intersection of humans with rodent-deer life cycle of B. burgdorferi infected ticks emergence of Lyme disease in humans Guanarito region of central Venezuela Humans in contact with excretions of infected rodents Venezuelan hemorrhagic fever Central railroad in Brazil Aswan High Dam in Egypt New snail habitat schistosomiasis Aswan High Dam in Egypt Indigenous mammals displaced Kissing bugs feeding on humans Chagas disease Flood lands Mosquitoes Rift valley fever Establishment of piggeries close to tropical forest in Malaysia Nipah virus from fruit batspigs pig farmers Ecological disturbances Deforestation A village with a high incidence of leishmaniasis. Leishmaniasis is a protozoan infection transmitted by infected sand flies. Sand flies are poor fliers, but they can traverse the short distance from their forest habitat. Leishmania Deforestation The interspecies leap. AIDS, which originated in Africa, is presumed to have jumped the species barrier from infected monkeys to humans. HIV Hurdles to interspecies transfer Pathogen must adapt in such a way as to be able to replicate in human cells, a complex problem Hantavirus, Nipah virus, WNV, and avian influenza virus Humans are a dead-end host It must be able to configure itself so that it can be transmitted from human to human HIV, SARS, Viral hemorrhagic fevers Ecological disturbances Climatic changes including global warming may favor the outbreak of many infectious diseases: Vibrio parahaemolyticus - ocean borne Malaria - mosquitoes Rift Valley fever - mosquitoes Hantavirus - mice Cholera - waterborne Hepatitis - waterborne Lyme disease - ticks Dengue fever - mosquitoes Cryptosporidosis - waterborne Ecological disturbances Climatic changes are likely to particularly effect vectorborne diseases (diseases carried to humans by arthropods) May effect the vector May effect the microbe Disease Malaria Population at risk, millions Prevalence of infection Present distribution Possible change of distribution as a result of climatic change 2,100 270 million Tropics, subtropics Highly likely Lymphatic filariasis 900 90.2 million Tropics, subtropics Likely Onchocersiasis 90 17.8 million Africa, Latin America Likely Schistosomiasis 600 200 million Tropics, subtropics African trypanosomiasis 50 25,000 new cases per year Leishmaniasis 350 12 million infected + 400,000 new cases per year Dracunculiasis 63 1 million Dengue NA NA Tropics, subtropics Yellow fever NA NA Africa, Latin America Likely Japanese encephalitis NA NA East and Southeast Asia Likely Other arboviral diseases NA NA Tropical to temperate zones Likely Tropical Africa Asia, Southern Europe, Africa, South America Tropics (Africa, Asia) Very likely Likely Not known Unlikely Arboviral diseases Very likely Ecological disturbances Natural disasters Flooding malaria and cholera in Africa Drought famine disease in Africa Increased humidity crop of pine needles mouse deer populationemerging Hantavirus infections in Four Corners area of U.S. Technological advances International travel – SARS, penicillin-resistant gonorrhea, monkeypox Approximate flying time from New York City Sydney, Australia: 22 hours (1 stop) Tokyo, Japan: 14 hours (nonstop) Tel Aviv, Israel: 10 hours (nonstop) Nairobi, Kenya: 16 hours (1 stop) Incubation period for selected diseases Whooping cough: 7-10 days Gonorrhea: 2-6 days Salmonella food poisoning: 8-48 hours Ebola fever: 4-16 days Measles: 12-32 days Chicken pox: 10-23 days It’s a small world after all. In a span of a couple of days, President Bill Clinton demonstrated the truth of this cliché. He flew from Washington to New York and back. Then he flew to Cincinnati, Denver, and Aspen. After briefly returning to Washington again, he flew to Morocco. From there he returned to Washington one more time. All that travel took place in one weekend. Technological advances Blood transfusions - hepatitis, HIV, malaria, trypanosomiasis, syphilis, Chaga’s disease. Organ transplants and immunosuppressive drugs - CMV, mad cow disease Microbial evolution and adaptation Antimicrobic resistance In the last 50 years antibiotics and antimicrobics have saved the lives of innumerable individuals with infections However now the microbes are becomimg resistant to antimicrobics - why? GROSS MISUSE of antimicrobics Microbial evolution and adaptation • Development of antimicrobic resistance: Developing countries Developed countries Insufficient use of antimicrobics Overuse of antimicrobics Too expensive Available virtually on demand Save it for a rainy day Used when not necessary Failure to complete dose Failure to complete dose Antimicrobic resistance Emergence of antimicrobial drug resistant bacteria Increasing resistance of selected pathogens Methicillin resistant Staphylococcus aureus Microbial evolution and adaptation Examples of drug-resistant diseases: Bacterial disease Viral disease Protozoan disease Typhoid fever HIV infection Malaria Tuberculosis Hepatitis B Visceral leishmaniasis Gonorrhea Staphylococcal infection Shigellosis Pneumococcal infection Enterococcal infection Microbial evolution and adaptation Microbes change their surface structures to evade host defenses Antibody can bind to antigen Antibody can’t bind to antigen Changing one’s coat. Trypanosomes and other microorganiams can form new surface antigens not recognized by antibodies. This is an important evasion strategy. Microbial evolution and adaptation Acquisition of new proteins introduced by lysogenic bacteriophages Mutations and evolution of viruses. Toxins produced by Streptococcus pyogenes that lead to necrotizing fasciitis (flesh eating bacteria). Mainly RNA viruses Include Ebola virus, SARS virus, Hantavirus, Avian influenza virus More on this later Adaptation of insect vectors Mosquitoes become resistant to DTT Malaria ? West Nile virus Human behavior and attitudes Complacency - “it can’t happen to me” Return to risky sexual behavior and AIDS and gonorrhea Failure to immunize your children - measles Failure to get immunizations when traveling to foreign countries - yellow fever and malaria Human behavior and attitudes Human migration -wars and conflicts resulting from political differences result in refugees or internally displaced persons who move from one part of the country to another A refuge camp. Refuge camps are hotbeds of infection. Crowding and lack of hygiene and sanitation favor the incidence and transmission of disease Human behavior and attitudes Societal factors Increased numbers of women workers in child care centers Intestinal parasites Diarrhea Middle ear infections Meningitis Increased longevitynursing homes, day care centers for adults, and assisted living environments Food production and dietary habits lead to food-borne diseases Centralized food processing –E. coli from spinach Fast food and take-out restaurants Import of agricultural produce - hepatitis A from strawberries and onions from Mexico, Cyclospora from Guatamalan raspberries Human behavior and attitudes Tattooing and body piercing and Staphylococcus aureus infections: Tattooing and skin piercing. Tattooing and skin piercing are a risky part of popular culture. The skin is invaded, potentially resulting in serious infection because of he use of unclean instruments Take Home Message Infectious disease deaths decreased from the 1950s through the 1970s. Infectious disease deaths started to rise again in the 1980s. New, emerging, and reemerging infections are a major health problem today. The world population growth is central to the issue of emerging infections. Other contributing factors include: Urbanization Ecological disturbances Technological advances Microbial evolution and adaptation Human behavior and attitudes Resources The Microbial Challenge, by Krasner, ASM Press, Washington DC, 2002. Brock Biology of Microorganisms, by Madigan and Martinko, Pearson Prentice Hall, Upper Saddle River, NJ, 11th ed, 2006. Microbiology: An Introduction, by Tortora, Funke and Case; Pearson Prentice Hall; 9th ed, 2007. Emerging Infectious Diseases. Michael A. Palladino, series editor; Benjamin Cummings speical topics in biology, 2006.