640 Infectious Disease Microbiology for Teachers

Respiratory Tract Infections

Background

• Anatomy and associated host defense factors
  • upper respiratory tract - nares (nostrils), oral cavity, pharynx (throat)
    • physical - sneezing, nasal hairs and mucus (filtration), continual sloughing of epithelium, flushing of oral cavity and pharynx by saliva
    • chemical - enzymes in saliva, mucus
    • cellular - phagocytes (PMN), normal microbiota
  • lower respiratory tract - epiglottis, trachea, bronchi, bronchioles, alveoli
    • physical - coughing, ciliated mucosal epithelium ("mucus escalator")
    • chemical - mucus, enzymes
    • cellular - phagocytes (alveolar macrophages)
• Epidemiology
  • transmission - personal interaction, respiratory droplets inhalation ... Respiratory Tract Infection Alert web site
  • predisposing factors - dry air, low exercise level, immunodeficiency

Respiratory Diseases

• Acute Common Coryza (Common Cold)
  • epidemiology: transmitted via respiratory secretions (both directly and indirectly), ~120 Rhinovirus strains, ~30 Adenovirus strains, Respiratory Syncytial Viruses, and others (coronaviruses, Coxsackie viruses, echoviruses, reoviruses) cause millions of colds each year in US ... especially in children
  • pathogenesis: nasal epithelial infection causes pharyngitis (cell damage, inflammation) which causes nasal secretions, sneezing, sore throat, coughing, fever (how to distinguish between colds and flu); complications - croup (persistent, hoarse cough in infants)
  • treatment: TLC - symptomatic relief; antibiotics not useful (treatment advice from a pharmacist)
  • prevention: avoid contact with respiratory secretions of infected persons

  Thrush

  • epidemiology: Candida albicans, a fungal member of normal microbiota, is an opportunistic fungus that frequently infects immunocompromised patients
  • pathogenesis: throat inflammation with superficial damage (unless the patient is immunocompromised, then infection is chronic and damaging)
  • treatment: nystatin
  • prevention: avoid broad spectrum antibiotics, immunocompromise

  Streptococcal Pharyngitis (strep throat)

  • epidemiology: Streptococcus pyogenes (bacterium); occurs mostly in children and young adults; frequently related to tonsillitis and its complications
  • pathogenesis: bacteria produce pyrogenic toxin which causes pharyngitis (cell damage, inflammation leads to sore throat, coughing); complications include scarlet fever ( more info), rheumatic fever and toxic shock syndrome ... check out the online diagnostic form for strep throat!
  • treatment: penicillin (erythromycin if patient is allergic to penicillin); symptomatic relief
  • prevention: avoid contact with respiratory secretions of infected persons

  Diphtheria

  • epidemiology: Corynebacterium diphtheriae (bacterium) - few cases in US due to vaccine-induced herd immunity (less than 10 cases per year in the US)
  • pathogenesis: pharyngitis (cell damage, inflammation leads to sore throat, coughing); diphtheria toxin causes pseudomembrane formation in the throat, then toxin goes systemic to cause heart, kidney and CNS damage (inhibits cellular protein synthesis); complications include paralysis, death; diagnosis
  • treatment: antitoxin, then penicillin
  • prevention: DPT vaccine @ 2, 4, 6, 18 months and Td vaccine boosters at 7-10 year intervals) ; avoid contact with respiratory secretions

  Pertussis (whooping cough)

  • epidemiology: Bordetella pertussis (bacterium) - human reservoir; ~7200 cases in US per year (~250,000 cases in 1950; low now due to vaccine use)
  • pathogenesis: 2-5 day incubation period leads to pharyngitis (cell damage, inflammation due to pertussis toxin causes sore throat, coughing), then progresses to bronchitis (loss of ciliated epithelial cells) causing bronchial accumulation of mucus and repetitive coughing; complications - 0.5-10% die
  • treatment: erythromycin
  • prevention: DPT vaccine @ 2, 4, 6, 18 months; avoid contact with respiratory secretions

  Influenza

  • epidemiology: Influenza Viruses cause 100-150 million cases per year in the US ... leading to 10,000-40,000 deaths each year (incidence this year); named from the Italian phrase influenza de freddo (influence of the cold); virus continually changes its surface structures by antigenic drift and antigenic shift, thus generating "new" strains which are able to infect people who had previously been infected with the "old" strains; this disease is the world's record-holder for the most people killed in the shortest time ... it spread throughout the world and killed more than 20 million people, beginning in March 1918
  • pathogenesis: after 1-4 days (average of 2 days), nasal epithelial infection leads to abrupt onset of rhinitis (inflammation causes nasal secretions, sneezing), then pharyngitis (inflammation causes sore throat, coughing), then bronchitis (due to ciliated epithelial cell loss) which leads to malaise, chills, fever, headache, nonproductive cough, muscle aches, joint soreness, weariness; the disease itself usually lasts for several (5-7) days, but the cough and malaise can last for 2 or more weeks ( how to distinguish between colds and flu); complications include primary influenza viral pneumonia or secondary bacterial pneumonia; together, influenza and pneumonia together constitute the number 7 killer in the US ... 63,686 people died of this combination in 1999 ... 1,663 of influenza and 62,023 of pneumonia); Guillain-Barre syndrome; Reye's Syndrome (aspirin induces Reye's Syndrome in children?)
  • treatment: TLC - symptomatic relief (but don't treat children with aspirin); amantadine prevents influenza A; neuraminidase inhibitors (Relenza, Tamiflu) reduce the chance of developing influenza by 70-90% (if taken within 48 hours of onset of signs and symptoms) ... more treatment info
  • prevention: vaccine ( who should get it? ... elderly, diabetics, anemics; cardiac, pulmonary, renal patients), avoid contact with respiratory secretions of infected persons

    Did ya know...?

    Influenza costs more than $20 billion per year in treatment and lost productivity in the US

  Pneumonia

  • epidemiology:
    • ~5 million cases reported each year in the US and ~65,000 of them die ... making pneumonia (in combination with influenza) the number 7 killer in the US (63,686 people died of this combination in 1999 ... 1,663 of influenza and 62,023 of pneumonia)
    • Streptococcus pneumoniae (this bacterium generally causes secondary infections); other bacteria, including Legionalla pneumophila, which causes Legionaires' Disease, and Mycoplasma pneumoniae or Chlamydia pneumoniae which both cause primary atypical or "walking" pneumonia; Pneumocystis carinii (opportunistic fungus that infects mostly immunocompromised individuals); Respiratory Syncytial Virus (causes disease mostly in children under the age of two)
    • Severe Acute Respiratory Syndrome (SARS) is a newly-emerging disease casued by a novel coronavirus ... As of 6/24/2003, WHO reported a cumulative total of 8458 cases of SARS, with 807 deaths (~10% mortality rate) in 32 countries (338 suspected and 75 probable SARS cases distributed among 41 states in the US) ... sadly, Carlo Urbani, the WHO epidemiologist who first figured out that a new microbe was starting to spread around the world died a few days after contracting the disease while studying it
    • Legionnaire's Disease is caused by Legionella pneumophila (first detected at an American Legion convention in 1976 in Philadelphia, when it was linked to inhalation of water droplets from water-cooled air conditioning systems); ~1000-1300 cases of this form of pneumonia (with malaise, myalgia, headache, cough and moderate fever) reported each year in the US, but there may be as many as 25,000
    • Hantavirus Pulmonary Syndrome is caused by Hantavirus, which is transmitted via inhalation of aerosolized deer mouse urine, feces or saliva; new strains emerged in four corners area of southwestern US in 1993; more than 180 cases of HPS in the US since then ... with ~50% mortality; this respiratory infection leads to development of fever, muscle aches, mild respiratory distress; complications include ARDS that develops about 5-6 days after initial onset of symptoms and causes sudden death due to fluid accumulation in the lungs (10-70% death rate)
  • pathogenesis: infection of alveoli leads to accumulation of fluid in lungs, which causes congestion (difficulty breathing, loss of energy, fever, cough, headache in some cases); complications include congestive heart failure, meningitis, death (up to 80,000 people in the US die of pneumonia each year ... this disease (together with influenza) is currently the number 7 killer in the US )
  • treatment:
    • CTAs for bacteria (penicillin for S. pneumoniae; tetracycline, erythromycin for Legionella pneumophila, M. pneumoniae, C. pneumoniae)
    • CTAs for P. carinii (pentamidine, sulfa drugs (SxT))
    • TLC ... symptomatic relief to minimize fluid accumulation in lungs for viruses, especially Hantavirus
  • prevention: vaccine (S. pneumoniae); avoid contact with respiratory secretions of infected persons ... especially those with influenza; disinfection of water-based evaporative air conditioning systems (L. pneumophila); avoid contact with deer mouse urine, feces or saliva (Hantavirus)

  Tuberculosis

  • epidemiology: Mycobacterium tuberculosis (bacterium ... aka tubercle bacillus or TB) - 10-20 thousand cases (and up to ~2000 deaths) per year in US; during the 1940s, ~100,000 cases each year (and ~40,000 deaths); there are ~2 billion TB infected people worldwide, with ~54 million new cases and 1.5-3 million deaths each year in the world ... TB is the leading cause of death from a single identifiable infectious disease, worldwide, and the main cause (26%) of preventable death people ages 15-40; it is especially prevalent in people with AIDS
  • pathogenesis: lung infection leads to granuloma formation, causes poor lung function (cough, bloody sputum, pain, lack of energy, weight loss, night sweats); complications include chronic progressive lung disease, death (50% mortality without treatment)
  • treatment:
    • 6-24 months combination CTA therapy (usually including rifampin, isoniazid and pyrazinamide)
      • Directly Observed Therapy Short-course (DOTS) strategy using daily combination therapy (up to four CTAs) for 6-8 months is used frequently
      • DOTS-Plus is a new approach in which patients take up to seven CTAs daily for 18-24 months (better cure rate)
    • there is much concern about drug resistant TB ... see where it is most problematic
    • with the currently recommended treatment, 249 million additional cases and 90 million deaths are predicted during the next 30 years
  • prevention: avoid contact with respiratory secretions of infected persons; early detection, treatment prevents spread; BCG vaccine (effective primarily against childhood TB) is used in parts of Europe and Asia

  Histoplasmosis

  • epidemiology: Histoplasma capsulatum (fungus) - inhalation of spores present in bird droppings transmits; 50,000-200,000 cases per year in US
  • pathogenesis: lung infection (5-18 days) leads to granuloma formation and causes loss of lung function (lack of energy) together with fever, chills, cough that brings up mucus or pus, and possible joint stiffness; very similar to TB, but less serious; complications - chronic, progressive lung disease, spread via blood to other organs (more likely in immunosuppressed people or in very young children); death
    • Chest X-ray showing granulomas
  • treatment: amphotericin B, ketoconazole or itraconazole
  • prevention: avoid contact with bird droppings (which contain spores)

  Otitis Media

  • epidemiology: Streptococcus pneumoniae, Haemophilus influenzae (bacteria) or various viruses; most often affects children aged 3 months to 3 years old, but may occur at any age
  • pathogenesis: microbes invade the middle ear via the eustacean tube, causing inflammation that results in swelling and fluid accumulation which can result in pain, fever, discharge and damage to the eardrum, causing impaired hearing (and sometimes affecting balance); complications include perforation of the eardrum or necrosis of the middle ear, leading to conductive hearing loss
  • treatment: antibiotics in conjunction with corticosteroids
  • prevention: avoid contact with respiratory secretions of infected persons

  Meningitis

  • epidemiology: Streptococcus pneumoniae (affects children most); Haemophilus influenzae (this bacterium mostly affects children 6 months to 2 years old); Neisseria meningitidis (~2500 cases per year ... affects young adults most); Listeria monocytogenes (actually infects via the gastrointestinal tract, but ends up causing the same syndrome as the others) - all these microbes are bacteria, but viruses and fungi can also cause meningitis; ~8000 cases of aseptic (viral) meningitis per year in the US
  • pathogenesis: damage to meninges (headache, coma) - complications include disseminated intravascular coagulopathy (DIC), kidney and skin damage, death (~250 per year in the US)
  • treatment: ampicillin (Haemophilus); penicillin ( Listeria, Neisseria, and Streptococcus); amphotericin B (fungi); TLC, symptomatic relief (viruses)
  • prevention:
    • vaccines
      • Hib vaccine induces immunity against meningitis caused by Haemophilus influenza b
      • Menomune induces immunity against major strains of Neisserial meningitis
      • Prevnar protects against Streptococcal meningitis
    • avoid contact with respiratory secretions of others

  Infectious Mononucleosis

  • epidemiology: Epstein-Barr Virus ( EBV) and Cytomegalovirus ( CMV) are transmitted by close oral contact (kissing); prevalent among teens in US; ~90% of adults in the US have antibodies against EBV
  • pathogenesis: First, sore throat (pharyngitis) with swollen glands (cervical lymphadenitis) and fever develops; then mononucleosis (monocytosis), muscle aches and fatigue develop; acute illness usually lasts 7-14 days, but it is important not to overexert for up to 6 weeks; complications include hepatitis, meningitis, myocarditis, paralysis, ruptured spleen, facial paralysis, chronic fatigue syndrome ("yuppie flu"), and death (rare)
    • EBV pathogenesis overview
    • CMV pathogenesis overview
  • treatment: TLC (much bed rest, little strenuous exercise, no alcohol)
  • prevention: avoid contact with respiratory secretions of infected persons

  Mumps

  • epidemiology: Mumps Virus is transmitted via respiratory secretions or saliva before symptoms appear; ~400 cases of mumps reported in the US each year (most age 5-10); ~one-third asymptomatic; down from 152,000 cases in 1968; the name comes from the English word "mump" (to sulk, to be sullen)
  • pathogenesis: parotid salivary gland infection causes fever, accumulation of saliva (parotid swelling, tenderness) after 16-18 days; complications - infection of ovaries, testes, thyroid, pancreas, CNS (meningitis, encephalitis, deafness)
  • treatment: TLC
  • prevention: MMR vaccine, avoid contact with respiratory secretions or saliva of infected persons

  Rubella (German measles)

  • epidemiology: Rubella Virus - transmitted via respiratory secretions before symptoms appear; ~300 cases normally reported each year in the US
  • pathogenesis: upper respiratory infection leads to systemic infection resulting in a mild skin rash ("rubella" = "red, small" rash)
    • Back of child with rubella

    complications - populations that don't get rubella vaccine have high miscarriage rates or congenital rubella syndrome (retardation, deafness, cataracts, glaucoma, heart defects) from fetal infection in first trimester of pregnancy

  • treatment: TLC
  • prevention: MMR vaccine; MMR vaccine; avoid contact with respiratory secretions

  Rubeola (Measles)

  • epidemiology: Rubeola Virus is transmitted via respiratory secretions before symptoms appear; ~100 cases of measles reported in US each year
  • pathogenesis: upper respiratory tract infection (10-14 days; "cold"-like symptoms) leads to systemic infection which results in Koplik spots, then skin rash with high fever, delirium; complications - blindness (vitamin A deficiency), pneumonia (4-7%), encephalitis, seizures, death (~10%; kills 1-1.5 million people per year worldwide); not teratogenic, but intrauterine rubeola infection can cause stillbirth, premature delivery, fatal congenital encephalitis; SSPE (subacute sclerosing panencephalitis)
  • treatment: TLC
  • prevention: MMR vaccine; avoid contact with respiratory secretions ... concerns about link with autism refuted

  Varicella ( Chickenpox)

  • epidemiology: Herpes Varicella-Zoster Virus is transmitted via respiratory secretions; most contagious human disease; ~3 million cases in 1999 in US (85% in 0-9 year-olds; 13% in 10-15 year-olds) ... 7000 hospitalized and 40 died
  • pathogenesis: upper respiratory tract infection ("cold"-like symptoms) leads to systemic infection, which causes fever, vesicular eruptions (lesions) of skin; complications - secondary bacterial infections (pneumonia, encephalitis (coma)), death (20% of adults); Reye's syndrome; congenital defects if infected during first trimester of pregnancy; later in life, shingles or zoster, which results from stress-induced activation of latent virus, leading to painful lesions on the skin or eye ... 700,000-900,000 cases of shingles every year in the US; mostly in the over-50 crowd, peak incidence at 60-79 years of age
  • treatment: TLC, symptomatic relief (for chickenpox - acetaminophen calamine lotion, acyclovir; for encephalitis, vidarabine (Vira-A) for shingles, Famvir (shortens chronic pain period), Zostrix (OTC analgesic)
  • prevention: vaccine; avoid contact with respiratory secretions of infected persons; varicella-zoster immune globulin (VZIG)

  Smallpox (variola)

  • epidemiology: Variola Virus - transmitted via respiratory secretions, vesicular fluid, or lesion crusts from infected persons; thought to be eradicated (last "wild" case in Somalia in 1977)
  • pathogenesis: upper respiratory tract infection leads to systemic infection (fever, chills, headache, backache) which leads to vesicular eruptions (lesions) of skin
    • Smallpox lesions on torso (from CDC)

    complications - disfiguration due to massive scar formation; death in severe cases (up to 90%) ...

    • bioterrorism information
      • CDC on bioterrorism
      • Center for Civilian Defense Studies on bioterrorism
  • treatment: TLC
  • prevention:
    • vaccine
      • we no longer vaccinate against smallpox because there is a bigger chance of harming those who are immunodeficient than there is of saving others (since the disease has been erradicated)
      • perhaps as few as 20% of those vaccinated a generation ago are still immune
    • avoid contact with respiratory secretions, vesicular fluid, or lesion crusts from infected persons

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  © 1997-2009 John R. Stevenson. All Rights Reserved
  

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  Please email questions and comments to:
  John R. Stevenson, Ph.D.
  Associate Professor
  Department of Microbiology
  Miami University
  Oxford, Ohio 45056
  USA

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  This document was last modified on Saturday, 04-Jul-2009 04:18:00 EDT