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; 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
pathogenesis: nasal epithelial infection causes
pharyngitis (cell damage, inflammation) which causes nasal
congestion and secretions, sneezing, sore throat,
and coughing (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
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); frequently cause of tonsillitis; complications include
scarlet fever, rheumatic
fever and toxic
shock syndrome
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
(fewer than 10 cases per year in the US); countries of the former
Soviet Union have reported >150,000 cases in an epidemic the began
in 1990; the Iditarod,
a ten-day dog-sled race commemorates a desperate race against time
to transport diphtheria antitoxin from Anchorage to Nome, Alaska,
during the 1925 epidemic; 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: DTaP
vaccine @ 2, 4, 6, 18 months and Td vaccine boosters at 7-10 year
intervals); avoid contact with respiratory secretions
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)
treatment: TLC (much bed rest, little strenuous exercise, no
alcohol)
prevention: avoid contact with respiratory secretions of infected
persons
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, i.e. CNS damage (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
avoid contact with respiratory secretions of others
Mumps
epidemiology: Mumps Virus is
transmitted via respiratory secretions or saliva before symptoms appear;
~6500 cases of mumps reported in the US each year (most age 5-10); ~one-third
asymptomatic; 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 (down from 152,000
cases in 1968), avoid contact with respiratory secretions or saliva
of infected persons
Rubella (German
measles)
epidemiology: Rubella virus is transmitted via respiratory secretions before
symptoms appear; ~10 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);
complications - congenital rubella syndrome (retardation, deafness,
cataracts, glaucoma, heart defects) from fetal infection in first trimester
of pregnancy
treatment: TLC
prevention: 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 (red and blotchy in people with light skin pigmentation;
fine granular eruption in people with dark skin pigmentation) 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)
treatment: TLC
prevention: MMR
vaccine; avoid contact with respiratory secretions ... MMR vaccine
does NOT cause autism!
Varicella (Chickenpox)
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: Varicella vaccine; avoid contact with respiratory secretions of infected persons;
varicella-zoster immune globulin (VZIG)
Pertussis (whooping
cough)
epidemiology: Bordetella
pertussis (bacterium) - human reservoir ... inhalation of respiratory droplets
containing the bacteria; ~15,000 cases in US per year (~250,000 cases in 1950; lower
now because of vaccine use)
pathogenesis:
1-3 week 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% death rate
epidemiology: Influenza
Viruses cause 100-150 million cases per year in the US
... leading to 10,000-40,000 deaths each year; named from the Italian
phrase influenza de freddo (influence of the cold); biology
of influenza virus; influenza 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;
current activity in the US; the newest influenza threat is avian
influenza
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 ...56,247 people died of this combination in 2006;
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)
prevention: influenza
vaccine (who
should get it? ... elderly, diabetics, anemics; cardiac, pulmonary, renal patients) avoid
contact with respiratory secretions of infected people
Pandemic
Flu: we are not prepared
Pneumonia
epidemiology:
~5 million cases reported each year in the US; 56,247 people died of pneumonia
(together with influenza)in 2006 ... making this combination the number 8 killer
in the US
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
jirovecii (formerly Pneumocystis carinii) an 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
treatment:
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 (Prevnar
for pneumococcal pneumonia);
avoid contact with respiratory secretions of infected persons ... especially those with influenza
Tuberculosis
epidemiology: Mycobacterium
tuberculosis (bacterium) - 13,299 cases (and ~1300 deaths) in
2007 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; etiology of TB was established
by Robert Koch in the late 1800s
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)
treatment:
6-24 months combination CTA therapy (often including rifampin and isoniazid)
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
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, Europe and Asia
Histoplasmosis
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)