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
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
or from a student health center)
prevention:
avoid contact with respiratory secretions of infected persons ... other
tips
epidemiology: Influenza
Viruses cause 100-150
million cases per year in the US ... leading to 10,000-40,000
deaths each year (~36,000/year 1990-1999); 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 in 18 months, beginning
in March 1918 ... Want to know where/when the flu is likely
to be worst in the US? Check out this site ... FluWatch!
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 8 killer in
the US (61,472 people died of this combination in 2004 ...
2.6% of all deaths); Guillain-Barre syndrome; Reye's Syndrome (aspirin
induces Reye's Syndrome in children?)
~5 million cases reported each year in the
US and ~1.3% of them die ... making pneumonia
(in combination with influenza) the number 8 killer in
the US (61,472 people died of this combination in 2004 ...
2.6% of all deaths in the US)
Streptococcus
pneumonia (this bacterium generally causes secondary
infection); other bacteria, including Legionalla pneumophila,
which causes Legionaires' Disease (2014 cases reported in
2003), 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)
SARS (severe acute respiratory syndrome) is caused by a newly-emerged
coronavirus (8 cases in 2003 in US)
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; when their death rates
are combined, influenza
and pneumonia constitute the number
8 killer in the US (61,472 people died of this combination
in 2004 ... 2.6% of all deaths)
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: S. pneumoniaevaccine -
prevnar for children, pneumovax
II for adults;avoid contact with respiratory secretions of infected
persons ... especially those with influenza; disinfection of water-based
evaporative air conditioning systems (L. pneumophila)
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)
treatment: TLC (much bed rest, little strenuous
exercise, no alcohol)
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
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
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
epidemiology: Mycobacterium
tuberculosis (bacterium ... aka tubercle bacillus or TB) ~15,000
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 active 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)
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
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)
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
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 million people
(mostly children) per year worldwide); not teratogenic, but
intrauterine rubeola infection can cause stillbirth, premature
delivery, fatal congenital encephalitis; SSPE (subacute
sclerosing panencephalitis)
epidemiology:
Herpes
Varicella-Zoster Virus is transmitted via respiratory
secretions; most contagious human disease; ~50,000 cases per
year in US (85% in 0-9 year-olds; 13% in 10-15 year-olds)
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; 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 (zovirax), famvir or
valtrex; for
encephalitis, vidarabine (Vira-A) or famvir
for shingles, Zostrix (OTC analgesic)
prevention:
vaccine (more
vaccine info); avoid contact with respiratory
secretions of infected persons; varicella-zoster immune
globulin (VZIG)
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%) ...
Chest X-ray showing granulomas
Smallpox lesions on torso (from CDC)