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Introduction to Human Diseases

Introduction to Human Diseases. Infectious Diseases Chapter 4. Definitions:. Infection A disease caused by microorganisms, especially those that release toxins or invade body tissues Most common microorganisms are bacteria of all kinds, viruses, fungi, protozoa, helminths

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Introduction to Human Diseases

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  1. Introduction to Human Diseases Infectious Diseases Chapter 4

  2. Definitions: • Infection • A disease caused by microorganisms, especially those that release toxins or invade body tissues • Most common microorganisms are bacteria of all kinds, viruses, fungi, protozoa, helminths • Communicable or contagious • Able to be transmitted from one individual to another • Modes of transmission • Droplets, touch, fecal-oral, blood products, sexually transmitted, etc.

  3. Factors that increase the prevalence of infectious diseases • Microbial adaptation & change • Host susceptibility • Climate, weather, changing ecosystems • Host demographics & behavior • Travel & commerce, technology & industry • Economics, land development • Poverty, war, famine, political issues • Breakdown of public health measures • Biological warfare

  4. Malaria • Protozoa in infected mosquitoes transmitted to human via bite • Live in/ develop in hepatocytes & RBC • Cause hemolysis, fever, chills, body aches, anemia, jaundice, “black water fever” • Dx: via blood smear • Rx: antimalarial drugs vary with region, now many multidrug resistant strains,

  5. Malaria • High-risk areas • subSahara Africa, SE Asia, Central & South America, Middle East, India • Malaria resistance associated with sickle cell anemia trait and disease • Prophylactic medication advised • Prevention is key • Insect repellant, mosquito nets, clothing, etc.

  6. Malaria: More Information • 300-500 million cases worldwide • Most in subSahara Africa • Annual mortality: 2 million • US cases: • 1300 cases/yr (travelers, military, immigrants) • Antimalarial medications: • Chloroquine, quinine, hydroxychloroquine (Plaquenil), mefloquine, doxycycline

  7. West Nile Virus (WNV) • Mosquito bites birds infected with WNV • Mosquito transmits WNV to human host • First noted in No. America in 1999 • Clinical features: • 80% asymptomatic • 20% mild viral-like syndrome • 1 / 150 encephalitis

  8. West Nile Virus (WNV) • Incubation period (post-bite): 3-14 days • Usual symptoms: • Fever, headache, myalgias, nausea, vomiting • Lymphadenopathy, skin rash • Encephalitis: • Additional nuchal rigidity, stupor, coma • Seizures, paralysis, vision loss, paresis

  9. West Nile Virus • Populations at greater risk: • Patients over 50 YOA • Patients spending more time outdoors • No specific treatment • Prevention measures • Prevent mosquito bites

  10. Smallpox (Variola) • Infection by Orthopoxvirus genus • Formerly epidemic illness • Vaccine (innoculation with milder cowpox virus) in 1796 by Edward Jenner • Brought to New World • Last known case in October 1977 • Declared eradicated in 1980 by WHO • Now exists only in labs, a bioterrorism agent

  11. Smallpox • Spread by inhalation of droplets • Virus =largest animal virus • Some larger than bacteria • Reproduce in respiratory tract epithelium • Then series of viremias • First minor viremia, then massive • Spreads to skin, intestines, lungs, kidney, and brain • Virus remains viable on surfaces for 1 week

  12. Smallpox • Incubation period 7-17 days • Signs and symptoms • Fever, chills, HA, backache, malaise, vomiting • Characteristic rash • Sequential: papule, vesicle, pustule • Deep seated pustules (14 days) • Scarring • Most contagious just after rash appearance

  13. Smallpox • Diagnosis • Culture of viruses from skin lesions • Treatment • Supportive, non-specific • Mortality • 30% (prior to 1980)

  14. Anthrax • Known since ancient times • Described in classic literature of Greeks, Romans, Hindus and Book of Genesis • Most common today in: • Middle East, India, Africa, Asia, Latin America

  15. Anthrax • Disease of herbivores largely • Infection with Bacillus antracis • Spores: remain indefinitely in environment • Toxins made by bacillus • Higher risk populations: • Work with leather, hides, meats • Vets • Animal handlers, herders

  16. Anthrax • Three forms: • Cutaneous • Mortality less than 1% with treatment • Inhalational • Mortality approximately 45% with or without treatment • Gastrointestinal • Very rare in US • Consumption of contaminated meats

  17. Anthrax • Cutaneous form (incubation: 1-7 days) • “malignant pustule” • Central coagulation necrosis (ulcer) • Thin rim of vesicles • Black eschar at ulcer site • Spread from lesion via lymphatics • Into bloodstream from liver, spleen, kidney • Remains in capillaries of infected organs

  18. Anthrax • Inhalational form • Inculation beriod of 1-3 days • S/S at first: nonspecific fever & cough • Then period of improvement • Rapidly progressive deterioration of respiratory failure

  19. Anthrax • Treatment • Nonbioterrorism • Penicillin • Bioterrorism • Quinolone (Cipro) • Doxycycline • Clindamycin (addition) for antiexotoxin effect

  20. Hantavirus Pulmonary Syndrome • Potentially lethal viral illness • First identified in Korean War • Named after Hantaan River in Korea • Old World strain, also in Russia & Scandanavia • Increasing concern in US over last 12 or more years • Four Corners area cases, 1993

  21. Hantavirus • Rodents are reservoir • Vector is often the deer mouse • Infection via inhalation of infected rodent saliva, feces, urine, etc. • Outbreaks in spring & fall (farming cycles)

  22. Hantavirus Statistics • National annual incidence: • 20-30 cases • Most risk in • Four Corners area, No. Idaho, Dakotas, E. WA, some parts of CA • Seen in 31 states

  23. Hantavirus Cardiopulmonary Syndrome (HCPS) • Old World Hantavirus infection: • Fever, hypotension, renal failure, thrombocytopenia & DIC (bleeding) • HCPS: • More virulent form • Fever, myalgias, then cough & dyspnea • Finally cardiovascular collapse • Initial mortality was 80%, now 30%

  24. Hantavirus Cardiopulmonary Syndrome • Most deaths within 24 hours of admission • Incubation period from 1-5 weeks • COD: sudden noncardiogenic pulmonary edema • Recovery is equally precipitous • Sequelae: several months of fatigue and decreased exercise tolerance • Treatment: supportive

  25. Lyme Disease • Infection with tick-transmitted spirochete • Borrelia burgdorferi • Tick host is field mouse, white-tailed deer • Tick must be attached for 2-3 days for infection • 30% pts do not recall tick bite • Reportable disease • 90%+ cases are on east coast

  26. Lyme Disease: Phases • 1. Erythema chronicum migrans (ECM) • Near or on bite, lasts 2-3 weeks w/o Rx. • 2. Malaise & fatigue • Only 2/3rds proceed to next phase • 3. Arthritis (within 6 mos of ECM) • Migratory, polyarticular at first • Evolves into monoarticular • Knee, ankle or wrist

  27. Lyme Disease: • Other S/S: • CN palsy, carditis, meningitis, chronic arthritis, chronic neuropathy • Bimodal age pattern of incidence: • 5-9 YOA and 50-54 YOA • Treatment: • Tick removal & one dose Doxycycline within 72 hrs or 30 days of Doxycycline

  28. E. Coli O157:H7 • E. Coli • Facultatively anaerobic gram negative bacillus • Exists as normal flora in GI tract and is throughout many environments • Five main pathotypes • The most common enteropathogen in developing countries • Traveler’s diarrhea, etc.

  29. E. Coli • Cause of many types of illness • Diarrheal illnesses • Most common, more serious disease in pediatrics • Hemolytic-uremic Syndrome • Microangiopathic hemolytic anemia, renal insufficiency, & thrombocytopenia • Urinary tract infections (UTI’s) • Neonatal sepsis & meningitis

  30. E. Coli • Various pathotypes • Some invasive (GI), other make toxin • Sources of infection: • Contaminated meat, water, stool of infected person • Treatment: • Varies with particular disease

  31. E. Coli • Note: Antibiotics for diarrheal illness increase the risk of HUS • Prevention: • Cook meat to internal temp of 160 degrees • Pasteurized milk and juices • Handwashing and cleaning of food, utensils

  32. Multidrug Resistant Organisms • Methicillin-resistant Staphylococcus aureus

  33. Methicillin-Resistant Staphylococcus aureus (MRSA) • First seen in 1960 • Now colonizes 25-65% US population • Both hospital-acquired (HA) and community acquired (CA) forms • Distinction is less clear now

  34. MRSA • Colonization sites: • Nares most common • Axillae, groin, GI tract • Most common infections: • Abscesses and cellulitis • Common recurrences • Multiple sites

  35. MRSA • Risk factors for infection with MRSA: • History of colonization with MRSA • History of recent MRSA infection • Known close contact with person colonized or infected with MRSA • Incarceration • Military service • Athletes • IV drug use

  36. MRSA • Treatment: • Surgical drainage of abscesses • Antibiotic use (Sulfa, clindamycin, doxycycline) • Prevention: • Hand hygiene, daily washing of laundry, personal items, nasal application of topical mupirocin, systemic antibiotics (rifampin)

  37. Upper Respiratory Infections • URI’s, acute coryza, “common cold” • Most common acute out-patient illness • May be viral or bacterial etiology • Usually mild, self-limiting disease • Affects nasopharynx, pharynx, larynx, trachea

  38. URI • Person to person spread • Inhalation of droplets • Touching infected person, tissues, etc • Virus or bacteria directly invades mucosa • Incubation period varies with infecting organism (usually 1-7 days) • Highest incidence in fall and winter

  39. URI • Peak incidence of nasopharyngitis • Less than 5 years of age • Peak incidence of pharyngitis • 4-7 year olds • Group A strep accounts for 5-15% of all pharyngitis (strep throat) • Treatment: supportive

  40. Influenza • Respiratory infection due to influenza virus • Orthomyxoviridae, SS RNA viruses • Three antigenic types: A, B, C • Epidemic disease • Pandemic of 1918-19 • 20-50 million deaths worldwide • Over one half million deaths in US

  41. Influenza • Spreads by inhalation of infected respiratory secretions • Virus invades upper airway and lower respiratory tract cells • Systemic S/S are due to inflammatory mediators • Incubation period: 18 hrs to 3 days

  42. Influenza • Signs and Symptoms • Often abrupt onset • Fever (100-104 degrees F) • Myalgias • Weakness and severe fatigue (prostration) • Sore throat, initially mild cough and rhinitis that worsen • Pleuritic chest pain

  43. Influenza • Peak season: November through March • Duration illness: classically 5 days • Mortality: 20,000 deaths annually • Extremes of ages at higher risk • Prevention: annual immunization • Treatment: antiviral drugs • Amantadine, Tamiflu, Relenza, etc.

  44. Severe Acute Respiratory Syndrome (SARS) • Infection with Coronavirus family • Coronavirus is 2nd most common cz of URI’s • Higher death rate than influenza and other URI’s • Begins as flu-like illness and may progress to pneumonia, respiratory failure, death

  45. SARS • Originated in Guandong province of southern China • Spread to Hong Kong, SE Asia, Canada and US in 2002-3 • No new cases since July 2007 • SARS probably originated in livestock and small mammals and spread to people

  46. SARS • Transmission via close person-to-person contact • Droplet inhalation or touch • Household contacts of SARS patients, caretakers, some airplane contacts • Incubation period usually 2-7 days • Some reports as long as 10-14 days

  47. SARS • Stage 1—flu-like prodrome • Fever, myalgias, fatigue • Diarrhea possibly • Duration 3-7 days • Stage 2—Lower respiratory phase • Starts 3 or more days after resolution Stage 1 • Nonproductive cough, dyspnea, progressive hypoxemia, abnormal CXR, respiratory failure

  48. SARS • Treatment: • Supportive, non-specific • Mortality: • Overall: 10% • Geriatric: over 50% • Quarantine (containment) period: 20 days

  49. Chronic Fatigue Syndrome (CFS) • Disease of unknown etiology • Probable infectious basis with immunological manifestations • Clinical criteria: • Fatigue of at least 6 months duration • Cognitive difficulties • Also called encephalomyalgia

  50. CFS • Demographics: • Females more than males • Young to middle-aged patients • Diagnostic testing: • No specific test proves diagnosis • High serum IgG levels to various viruses • Diagnosis of exclusion • CFS is not EBV infection

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