epidemiology: transmitted via respiratory
secretions (both directly and indirectly), ~120
Rhinovirus
strains, ~30 Adenovirus strains, Respiratory
Syncytial Viruses (more
about RSV), and others
(coronaviruses, Coxsackie viruses,
echoviruses, reoviruses) cause millions
of colds each year in US ... especially
in children; Severe
Acute Respiratory Syndrome (SARS) emerged in China in 2003; this
disease is casued by a novel coronavirus
(SARS-CoV) ... WHO reported that 8,098 people worldwide developed
SARS during the 2003 outbreak, and 774 of them died; the most recent cases of SARS were
laboratory-acquired infections in China in April 2004
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
epidemiology:
Corynebacterium diphtheriae (bacterium) - few
cases in US due to vaccine-induced "herd" immunity
(fewer than 10 cases per year in the US); Elisha Otis,
the inventor of the elevator, died of diphtheria; countries of the former Soviet Union
have reported >150,000
cases in an epidemic the began in 1990
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
treatment: antitoxin, then penicillin
prevention: vaccine (DPT
vaccine @ 2, 4, 6, 18 months and Td
vaccine boosters at 7-10 year intervals);
avoid contact with respiratory secretions
epidemiology:
Bordetella pertussis (bacterium) - human
reservoir; 25,616
cases in US during 2005 (~250,000 cases in 1950;
lower now because of 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
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 9 killer in the US ...50,003 people died of this combination in 2004;
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) shorten length of
illness by one day (if taken at onset of signs and
symptoms) ... more
treatment info
~5 million cases reported each year in
the US; 50,003 people died of pneumonia (together with influenza) in 2010 ... making this combination the number
9 killer in the US
Streptococcus
pneumonia (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)
pathogenesis:
infection of alveoli leads to accumulation of fluid in
lungs, which causes congestion (difficulty breathing,
loss of energy, fever); complications include
congestive heart failure, meningitis, death
CTAs for bacteria ... penicillin for
S. pneumoniae; tetracycline or erythromycin
for M. pneumoniae, C. pneumoniae, or L.
pneumophila
CTAs for P. carinii ...
pentamidine, sulfa drugs (SxT)
TLC, including symptomatic relief,
for viruses such as RSV
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)
epidemiology:
Mycobacterium tuberculosis (bacterium) -
14,097 cases (and ~1500 deaths) in 2005 in the US;
during the 1940s, ~100,000 cases each year (and
~40,000 deaths); there are now ~2 billion infected
people worldwide,
with ~8 million new cases and ~3 million deaths each
year in the world ... TB is the leading cause of death
from a single identifiable infectious disease in the world as a whole, and the main cause
of preventable death people ages 15-40
pathogenesis: survives
inside macrophages; chronic
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)
epidemiology:
Histoplasma capsulatum (fungus) - inhalation of
spores present in bird droppings transmits;
~500,000 new cases per year in US; highest incidence
in people between 15-34 years old; H. capsulatum infections clustered
geographically (primarily SE 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 ... mortality rate of 0.05
per 100,000 (138 deaths per year)
treatment: amphotericin B, ketoconazole or
itraconazole
prevention: avoid contact with bird
droppings (which contain spores)
