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Chapter Outlines

Chapter 18      Emerging (New) and Re-emerging Viruses

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18.1 Viral Factors: Evolution and Adaptation Emerging virus: new or recently identified virus to humans Reemerging virus: a virus under control from a public health perspective but is making a comeback or reappearance and increasing in incidence and geographical range of exposed human populations Recent Viral Outbreaks in the News Avian Influenza H5N1 Mumps Chikungunya Fever Poliomyelitis in an Amish community Norovirus on cruise ships, in hospitals, hotels, public gatherings Bluetongue virus 3 Types of Factors that Play a Key Role in Influencing Disease Emergence Viral Human Ecological Mutation rate of RNA viruses: 1 mutation per every 104 to 105 nucleotides Mutation rate of DNA viruses: 1 mutation per every 108 to 1011 nucleotides Influenza viruses - antigenic drift Recombination Reassortment or gene swapping or antigenic shift (Influenza viruses) 18.2 Human Factors Human demographics: Sex/gender Race/ethnicity Mobility/travel Occupation Sexual behavior Socioeconomic status Geographic location Family size Population Growth: Density and Crowding Human populations leads to urbanization (migration of people from the countryside to cities) Higher population densities favor the spread of viral diseases. Crowding Sanitation Contamination of drinking water Healthcare facilities Human Movement: Viruses Live in a World Without Borders Air travel allows infected travelers to reach any part of the world in less than 24 hours. SARS pandemic H5N1 Avian flu pandemic? The spread of viral diseases to new areas can happen at any time. WHO Report of Human Cases and Deaths of Avian Influenza. See Table 18-2. Nations Confirmed Cases of H5N1 Influenza in Poultry and Wild Birds. See Figure 18-4. U.S. Geological Survey's National Wildlife Center, Madison, WI Monitors samples taken from migratory waterfowl for avian influenza viruses Early warning system to agriculture, public health and wildlife communities Speculate that the H5N1 strains will enter North America through the Pacific flyway Cruise vacations increased by 50% from 1993-1998 In North America, 6.8 million passengers board cruise ships each year Floating minicities with constantly changing populations of people in a confined space Increase in gastrointestinal illness caused by noroviruses Norovirus Outbreaks 2002 new norovirus variant emerged in hospitals in the UK and Ireland and on U.S. cruise ships Noroviruses cannot be cultured in the lab No animal model for noroviruses Hard to determine the genetic changes in the virus that triggers outbreaks that are more severe CDC started the Vessel Sanitation Program (VSP) in the early 1970's as a result of several disease outbreaks on cruise ships Vessel Sanitation Program Routine inspections of: Water supply Spas and pools Food Employee hygiene practices General cleanliness and physical condition of the ship Training programs Viruses Without Borders: War, Famine, Natural Disasters Refuge camps and temporary shelters Poor sanitation Crowding Lack of assess to clean water Poor nutritional status of people Limited medical care Aircraft - way to move: Virus-infected animals Arthropod vectors (e.g. mosquitoes) West Nile Virus (WNV) Leading theory is the WNV - mosquitoes flew across the Atlantic Ocean from Israel on aircraft Aircraft cabin spaces were not routinely sprayed with insecticides on intercontinental flights entering the U.S. WNV Human, Avian, Animal Cases or Mosquito Infections in 1999. See Figure 18-6. WNV Human, Avian, Animal Cases or Mosquito Infections in 2006. See Figure18-6. WNV Transmitted to Humans Via 4 Novel Routes Blood transfusion Organ transplantation Transplacental transfer Breastfeeding Human Exposure to Zoonotic Diseases: Pasture, Hunting and Fishing Practices Zoonoses-infectious diseases transmissible from animals to humans or from humans to animals Zoon (animal) and nosos (disease) Zoonotic Disease Statistics 208 human pathogenic viruses or prions 77 (37%) of these are emerging or reemerging pathogens 56 of the 77 (73%) of the emerging or reemerging pathogens are known to be zoonotic Crossing the Species Barrier Close proximity of wildlife to humans may contribute to viruses crossing the species barrier Monkeypox, U.S. exotic pet trading (praire dogs) Free-Range Farming Method of farming in which animals or birds are allowed to roam freely instead of contained in any manner Common in small rural farms in Asia Live Markets Wild animals are captured and sold in live markets or kept in cages in restuarants waiting for consumption. Chinese culture: fresh foods made from wild animals are considered a delicacy called "wild taste." Beavers, badgers, civet cats, domestic cats, hares, raccoon dogs, snakes and pangolin. Animals which may be infected are in stacked cages--their blood, secretions, feces and urine contaminate the cages. Food handlers subsequently butcher the animals while having direct contact with the fluids. SARS outbreak, 2003, Southern China Example of a live market transfer from animal to humans Infected civet cat/chefs and food handlers? Natural reservoir is likely the Chinese horseshoe bat Bushmeat Bushmen hunting animals for food Slaughter pathogen-infected nonhuman primates Bushmen come in contact with raw bushmeat, blood, bodily fluids of the butchered animals (also SIV) See Chapter 16 on the origin of HIV Viral Hemorrhagic Septicemia (VHS) Virus Serious pathogen of fresh and saltwater fish. Cause of an emerging disease in the Great Lakes region of the U.S. and Canada Infected fish show signs of: Bulging eyes Hemorrhaging in the eyes, gills, skin and the base of the fins Bloated abdomens Inactive or overactive behavior Genetic tests show that this VHS strain likely came from the Atlantic Ocean located near New Brunswick, Canada VHS Declared a Federal Emergency in 2006: Major Fish Health Crisis U.S. Dept. of Agriculture's Animal and Health Inspection Service (APHIS) issued the emergency Banned the importation of 37 species of live fish from 2 Canadian provinces into the U.S. VHS Biosecurity and Preventative Measures Rinsing boats and any other equipment that have been in VHS waters with hot water or drying it for at least 5 days Never moving fish eggs or live fish to other waters Reporting fish dieoffs to the local Department of Natural Resources (DNR) representative or conservation warden Cleaning and disinfecting all fishing gear Agricultural Practices, Deforestation, and Dam Construction Agricultural practices: The extension of farmland into unused land exposes farmers to zoonotic diseases (especially rodents carrying viruses) Example: 1958-1974, Argentine hemorrhagic fever (caused by Junin viruses carried by rodents) Deforestation Removal of trees in forests (e.g. Amazon) 2005 Brazil, vampire-bat related rabies 1998-1999 Malaysia, Nipah virus infecting pigs, humans, dogs and cats 1994-1995 Australia, Hendra virus infecting racehorses, horse trainers, and stablehands 2006, China, Porcine Reproductive and Respiratory Syndrome (PRRS) Also referred to as "blue-ear pig disease" Becoming one of the most important economically significant diseases The virus attacks macrophages, crippling their immune system (allows viruses and other pathogens to do damage e.g. severe pneumonia) China strain is particularly virulent Virologists are concerned that this virus may cross the species barrier from pigs to humans Dam Construction 1930's - several mosquito-borne outbreaks of viral diseases during dam construction 1987 -Rift Valley Fever in Mauritania occurred after a dam was constructed on the Senegal River (West Africa) Global Commerce Buying and selling of foods occurs between nations Developing countries may contain viral contaminants through the use of raw human sewage as fertilizer Hepatitis A Noroviruses Enteroviruses Astroviruses Rotaviruses Coronaviruses Most commonly contaminated foods are iceberg lettuce, strawberries, raspberries, green onions, diced tomatoes, shredded cabbage, raw oysters Colony Collapse Disorder (CCD) of Bees 2006-2007: 23% of beekeeping operations in the U.S. suffered from CCD Metagenomic survey results: Israeli Acute Paralysis Virus (IAPV) fouind in 25 of 30 CCD hives and only 1 of healthy hives IAPV likely imported into the U.S. with infected bees from Australia Importing Animals for Biomedical Research and Vaccine Production 1967, Infected African green monkeys imported to Marburg, Germany and Belgrade, Yugoslavia for research and preparation of poliovirus vaccine Monkeys infected with Marburg virus - cause of hemorrhagic fever in humans (high mortality rate) First people infected were laboratory workers who had contact with monkey blood or organs or prepared cell cultures. Human Social Behavior: Sex and Intravenous Drugs Multiple sex partners increases risk of acquiring STDs such as HIV, Hepatitis B and C and human papillomaviruses. HIV spread primarily via homosexual contact or by sharing contaminated needles used for intravenous drug use. Human Social Behavior: Cultural Traditions 2005 Marburg Hemorrhagic Fever Outbreak in the Angolan province of Uige 374 cases, 329 deaths First victims were hunters who ate an infected monkey. Traditional funeral rites of washing kissing the body spread the virus via blood-to-blood contact. Human Social Behavior: Research Laboratories Research on dangerous pathogens is performed in BSL-3 and BSL-4 laboratories. The chances of a viral pathogen "escaping" are rare. Mishap with a Deadly Influenza A Virus In 2005, an Asian H2N2 Influenza A virus strain present in diagnostic kits was sent to thousands of labs in different countries. This strain caused a pandemic in 1957-1958. Anyone born after 1958 would have little or not immunity. Within days, all packages of the kits containing the deadly strain were recovered and destroyed. Human Medicine and Susceptibility to Infection Health-related infections Unsafe medical practices (e.g. reusing syringes and overuse of antimicrobials) Blood transfusions Immunosuppression Xenotransplantation (See Chapter 9) Breakdown in public health measures (e.g. lack of vaccination, sanitation problems) Bloodborne infections are a problem in developing countries and developed countries (e.g. 2006, U.S. outpatient and long-term care facilities investigated because of several outbreaks of bloodborne illnesses) U.S. blood supply is excellent. HIV and HCV prevalent in Chinese communities 1980's-1990's contaminated blood supply (pooled blood for plasma) Immune-Comprised Populations U.S. had 10-20 million immune-compromised in 2006 Use of immune-suppressive drugs used during organ or bone marrow transplants Kidney dialysis Chronic corticosteroid treatment Chemotherapy Common Opportunistic Viral Infections Human cytomegalovirus Varicella zoster Herpes Simplex I Epstein Barr Virus Human Herpes Virus Type 6 Human Herpes Virus Type 7 Adenoviruses Hepatitis viruses Vaccine-Preventable Diseases are on the Rise in the U.S. College setting Measles Mumps Amish Community Poliomyelitis 18.3 Ecological Factors: Climate Variability Many emerging infectious disease outbreaks occur after environmental disruptions such as: Hurricanes Tsunamis Extreme floods Increase rainfall Droughts Global change continues Predicted rise of vectorborne diseases Examples of Viral Outbreaks Correlated with Environmental Changes 1993: 4 Corners Area, U.S. Sin Nombre hantavirus outbreak (deer mouse was the carrier of the virus) Correlated with rainfall increase, more pinon nuts (food for deer mice) 1999 West Nile Virus (WNV) outbreak, NYC Correlated with a dry spring and summer that decreased the mosquito predators and breeding sites Mosquitoes thrived in drainpipes and sewer puddles that attracted birds in search of water Mosquitoes fed on WNV-infected birds Reasons for the Emergence or Reemergence of Viral Diseases. See Table 18-3