Lecture 15 Emerging Infectious Diseases PDF

Emerging infectious Disease Disease of infectious origin whose incidence in humans has increased over the past two decades or threatens to increase in the near future Can be novel = unknown to man ○ re-emerging ○ Spreading beyond historic range Can be changing in virulence ○ Or adapting to pesticide...

Emerging infectious Disease Disease of infectious origin whose incidence in humans has increased over the past two decades or threatens to increase in the near future Can be novel = unknown to man ○ re-emerging ○ Spreading beyond historic range Can be changing in virulence ○ Or adapting to pesticide/frug-resistance Contributory Factors Adaptations of existing animal disease to new human host = zoonosis Transfer from one species to another ○ Known as crossing xenographic barrier Mobility of human populations transports diseases ○ Air travel = quicker then symptoms become apparent ○ Aggregates many people in close proximity Transport of raw materials ○ Introduces animal vectors and their pathogens Climate Change ○ expands habitable ranges/lengthens seasons of vectors and pathogens Public Health programs International ○ WHO Worldwide health has improved through eradication / reduction of diseases Contributes to population crisis however, overcrowding, inadequate sanitation, and overstretched public health infrastructures ○ Allowed expansion of diseases ○ Current = More people vulnerable to diseases than ever, and food insecurity Factors Contributing to the Emergence of Infectious Diseases 1. Ecological changes 2. Human Demographic Changes 3. Travel 4. Technology and Industry (globalization) 5. Microbial Adaptation/ change 6. Breakdown of Public Health measures Ecological changes Ag. And Suburban development ○ Local to regional ○ People expand to where host animals thrive ○ Animal host expand to human living areas ○ Mod. Of environment increases human-animal interactions ○ Decline in natural predators Climate ○ Regional to global ○ Extreme weather patterns from natural uctuations or man-made changes lead to disease outbreaks ◆ El Niño Dengue Hemorrhagic Fever Epidemeology ○ Complacency of mosquito programs has lead to return of dengue viruses ○ Greatest emergence in central and South America The Disease ○ Normal Dengue ◆ urban tropical disease ◆ Severe u-like symptoms ◇ Break-bone fever = severe body aches and pains ○ DHF fl ○ fl ◆ leaky capillary syndrome ◇ Blood vessels leak into tissue resulting in shock and death if not treated ○ Four antigenically distinct viral serotypes ◆ No protective cross-immunity for all 4, meaning a person can get multiple dengue infections ◆ Subsequent dengue infections are more likely to lead to hemorrhagic variety Current status ○ >3 billion people vulnerable ○ 80-100 million cases of dengue fever annually ○ Increased incidence by 30X from 1960-2010 Human demographic Changes urbanization ○ Uneven Pressure ○ 1900 = 5% world population. In cities ○ 2025 = 65% in cities, 70X more then 1900 ○ Increased population density in urban areas surpasses basic services ◆ Clean water supplies, sanitary conditions, adequate housing ○ Public health measures in overcrowded cities are strained or unavailable Public health paradox = Those most susceptible to infectious disease have fewest/worst facilities Travel Single largest factor allowing rapid spread of emerging diseases is transportation Increased economic activity internationally across boundaries has led to increase travel ○ Diseases without boundaries Severe Acute Respiratory Syndrome (SARS) Near pandemic 2002-2003 More susceptible the older you are for mortality 2003 = WHO identi ed coronavirus was of cial cause of SARS fi fi fi ○ Ful lled Koch’s postulates, was causative agent 2003 ○ Wild animals sold as food found with SARS coronavirus ○ Palm civets ○ virus crossed xenographic barrier from civets to humans 2004 = found in raccoons, badgers, and domestic cats 2005 = Chinese bats Conclusion ○ SARS coronavirus originated in bats and spread to humans directly form animals sold in markets ○ Bats = asymptomatic, but reservoirs of SARS Treatment ○ Fever reducers/ supplemental oxygen/ ventilator support ○ Steroid and other immune-modulating agents Technology and Industry Globalization ○ In uences on public health ○ Disease is moving rapidly around the globe since technology and economic interdependence has increased ◆ Travel ◆ Food processing ◆ Movement of raw and processed materials ◆ Medical technology Microbial Adaptation & Change past 70 years only cured one individual of communicable disease ○ Bred resistant microorganisms ○ Selected microorganisms with ability to develop resistance quickly Antibiotic Resistance ○ Wide distribution of antimicrobials ○ Antibiotic residue are detected in municipal WWTP ef uents fl ○ Hand sanitizer are generally ineffective fl ○ >80% antibiotic use in U.S. is for preventative treatment and growth promotion of livestock ○ First generation antibiotics ◆ Penicillin and tetracycline ◇ Now limited use ◇ Used in vet applicants ○ Vancomycin = drug of last resort Methicillin-resistant Staphylococcus aureus (MRSA) strain of bacterium Now resistant to many antibiotics Two types ○ HA-MRSA ◆ Healthcare-associated ○ CA-MRSA ◆ Community-associated HA-MRSA ○ Greater spectrum of drug resistance 1. Patients with open wounds, invasive medical devices, weak immune system at greater risk of infection 2. Hospital staff that dont follow proper sanitation can transfer Staph to patient 3. Visitors to MRSA patients advised to follow protocol to prevent infection CA-MRSA ○ Initial = red bumps, fever/rash ○ Bump turns into deep pus- lled boils ○ cause more severe illness then HA-MRSA ○ Can penetrate body wall to vital organs ○ Due to cytotoxins fi U.S. MRSA infection rates have increased signi cantly fi Spread of CA-MRSA antibiotic use in intensive animal farming MRSA bacteria found in water at beaches along Florida’s coastline Sand and beach water alone west coast MRSA at Risk Populations Weak immune systems ○ Children ○ Elderly ○ Patients Person in health care facility for n extended period of time People who spend time in con ned spaces with other people ○ Prisoners ○ Soldiers ○ College student in dorms Maryland not keep of cial records on # of MRSA cases Breakdown of Public Health Measures 18th and 19th century advancements in public health improved overall health of populations, especially in urban settings Public health and sanitation measures that minimized spread of infectious diseases in humans ○ Vector control ○ Chlorination of water ○ Pasteurization of milk ○ Immunization ○ Proper sewage disposal Complacency, distraction, re-prioritization, and distrust of science has lead to diseases fi returning from the lapse measure of the public health fi