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Introduction to Human Diseases

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1 Introduction to Human Diseases
Infectious Diseases Chapter 4

2 Definitions: Infection Communicable or contagious
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
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: No specific treatment
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 Treatment Mortality
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 Inhalational Gastrointestinal
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 Bioterrorism Penicillin
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: Bimodal age pattern of incidence: Treatment:
CN palsy, carditis, meningitis, chronic arthritis, chronic neuropathy Bimodal age pattern of incidence: 5-9 YOA and 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 Sources of infection: Treatment:
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: Most common infections: 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: Prevention: 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 Virus or bacteria directly invades mucosa
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 Peak incidence of pharyngitis
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 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 ( 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 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 days

47 SARS Stage 1—flu-like prodrome Stage 2—Lower respiratory phase
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: Mortality: Supportive, non-specific 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: Diagnostic testing: 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

51 CFS Clinical Syndrome: Often follows an infection
Associated with Type A personality Associated with depression due to CFS Short-term memory problems, verbal dyslexia Fatigue: often post-exertional, not relieved by sleep or rest

52 CFS Treatment: No medicines are effective
Changes in activity and daily routines are advised

53 HIV Infection & Acquired Immunodeficiency Syndrome
HIV (Human immunodeficiency virus) A Lentivirus, subgroup of retroviruses Known for latency, persistent viremia, nervous system infection, & weak host immune responses. High affinity for CD4 T-lymphocytes and monocytes Virus becomes internalized, becomes incorporated into host DNA

54 HIV Infection & AIDS First recognized in 1981 in NYC in homosexual men
Statistics: US: 944,000 AIDS dx so far Estimated 1 to 1.2 million asymptomatic HIV Worldwide: 20 million deaths to date

55 HIV Infection & AIDS Transmission: Sexual contact (over 70% cases)
More common in heterosexual males and females worldwide than homosexual males Parenteral contact IV drug use, contaminated blood products, occupational exposure to needlestick Perinatal transmission From maternal blood

56 AIDS: Diseases of immune compromise:
Virtually every organ can be involved Various malignancies Kaposi sarcoma, leukemias, lymphomas Opportunistic infections PCP (most common), fungal infections and thrush Syphilis, TB, Herpes zoster, histoplasmosis Cryptococcal meningitis and pneumonia

57 AIDS Diagnostics: Latency: Treatment:
CD4 count less than 200 cells/ mm3 Latency: Median of 11 years after infection Treatment: HAART (Highly active antiretroviral therapy) Prophylaxis against opportunistic infections

58 Measles (Rubeola) Viral etiology
Transmission via droplets (touch & inhalation) Incubation period: days Peak: winter and spring Most common in school-age children

59 Measles Signs and Symptoms: Rhinitis, slowing increasing fever
Koplik’s spots in mouth by Day 2-3 Cough, fever maximize Characteristic maculopapular rash that begins on the face and spreads inferiorly

60 Measles: Treatment: Prevention:
Supportive, fever control, fluids, etc. Prevention: Routine vaccinations Gamma globulin within 5 days of exposure Handwashing, etc.

61 German Measles (Rubella)
Viral etiology Incubation period: 2-3 weeks Most common in teenages & young adults Not as contagious as measles Severe fetal malformations for rubella in pregnant women

62 German Measles (rubella)
Clinical: Up to 50% cases are asymptomatic URI-like early symptoms Rash (papular or diffuse bright red) begins on face, spreads inferiorly, rapidly clears, may itch or peel Treatment: Supportive, fever & pruritis control, etc.

63 German Measles Prevention: Vaccination
Not in pregnant females or females trying to become pregnant within next 3 months Gamma globulin shortly after exposure Handwashing, etc

64 Fifth Disease (Erythema Infectiosum)
Parvovirus etiology Transmission via direct contact/secretions Incubation period: days Peak: winter & spring Most common in elementary and high school age patients Contagious prior to appearance of symptoms

65 Fifth Disease Clinical: Treatment: supportive
Flulike symptoms, red facial rash (slapped cheek appearance), lacy rash on rest of body, rash may recur 20-60% may be asymptomatic Treatment: supportive Prevention: hygiene & disposal of secretions

66 Mumps Etiology: paramyxovirus Incubation period: 18 days
Transmission: airborne/ droplets Peak: winter and spring Most common in school age children and young adults

67 Mumps: Clinically: Treatment: supportive Prevention:
Fever, parotitis and inflammation of other salivary glands, orchitis Treatment: supportive Prevention: Vaccination, avoid contact with mumps patients, hygiene & disposal of secretions

68 Chickenpox (varicella)
Etiology: a herpesvirus Incubation period: days Transmission: respiratory droplets & direct contact Most common in children

69 Chickenpox (varicella)
Clinical: Characteristic itchy rash, lesions in all stages of macules, papules, and vesicles, also fever Treatment: Supportive, antiviral medicines if used early in the course of disease Prevention: Highly contagious (avoidance, good hygiene, etc) Vaccination, VZIG within 3 days of exposure

70 Diphtheria Etiology: Corynebacterium diphtheriae
Incubation period: 2-5 days Most common in children less than 10 YOA Transmission: close contact with infected secretions and skin lesions Bacterial toxin affects heart, kidneys, peripheral nerves

71 Diphtheria Clinically: Fever, malaise Breath odor
Fragile membrane over posterior pharynx and other respiratory surfaces Symptoms of cardiac, renal, peripheral nervous systems

72 Diphtheria Treatment: Prevention:
Diphtheria antitoxin, supportive care Prevention: vaccination

73 Pertussis (Whooping Cough)
Etiology: Bordetella pertussis Incubation period: days Transmission: respiratory secretions Treatment: antibiotics (zithromax) at the early catarrhal stage Prevention: vaccination and disposal of contaminated secretions, etc.

74 Pertussis: Clinical Stages
Catarrhal stage URI-like symptoms, mild fever Paroxysmal stage 3-4 weeks, paroxysmal cough followed by stridor (whoop) Decline Gradual decrease of cough and other symptoms

75 Tetanus (lockjaw) Etiology: Clostridium tetani Source: soil mostly
Spores make toxin that acts on CNS and on voluntary muscles (contractions) Source: soil mostly Children at higher risk Prevention: Vaccination, protection against wounds and soil contact

76 Tetanus Clinically: abrupt or gradual onset
Stiffness of neck, jaw, esophageal muscles Later lockjaw (rigidity), vocal changes Facial muscle contractures (grimace) Spasm of back, extremities Finally fever, sweating, tachycardia, dysphagia, severe pain

77 Tetanus Treatment: Wound cleansing TIG Muscle relaxants, pain relief
Mechanical ventilation Often long-term care (6-7 weeks)

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