Description
SPHU 1020
Final Exam Review
Basic disease concepts and terms:
● zoonotic diseases: diseases spread between animals and people
● infectious disease control measures
○ WASH
● vectorborne diseases
Malaria
● pathogen: nonmotile protozoan of genus Plasmodium
○ singlecelled, nucleated
○ P. falciparum:
■ potentially fatal — infections cause most deaths
■ can lead to cerebral malaria, which has 1 to 2% mortality
rate
■ can progress rapidly to severe malaria even with
treatment
■ people in endemic areas can have some immunity
■ nonspecific symptoms
○ P. vivax:
■ benign, uncomplicated
■ most people from West Africa are resistant
■ main problem is tendency to relapse
■ acute symptoms
● symptoms:
○ acute — anemia, jaundice, tender liver/spleen, thrombocytopenia
○ general — malarial paroxysm (alternate periods with symptoms and
periods without symptoms), anemia, respiratory distress disease, fever, hypoglycemia, mental status changes, tropical splenomegaly
● transmission:
○ bite of infected female Anopheles mosquitoes
○ shared needles
○ transfusions
○ mothertofetus
● immunity:
○ innate immunity — first line of defense
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○ acquired immunity — mother to child transferred (36 months of
protection)
○ no complete immunity
● treatment and control:
○ personal protection measures
■ repellents with DEET
○ artemisininbased combination therapies (ACTs) Don't forget about the age old question of When does female defense polygyny occur?
■ some resistance to artemisinin, but ACTs still effective
in almost all settings
○ insecticidetreated nets (ITNs)
■ reduce child mortality by around 20%
○ indoor residual spraying (IRS)
○ intermittent prevention treatment of pregnant women If you want to learn more check out What is proven by the first law of thermodynamics?
HIV/AIDS
● movement from simians to humans:
○ consumption of bushmeat in Africa
○ HIV mutated in 1930s from a form exclusive to apes to one possible in
humans
○ first human case found in African man 1959
● transmission:
○ sexual contact with infected partner If you want to learn more check out If someone buys a lemon car, do they get their money back?
○ contact with contaminated blood or blood products
○ sharing bloodcontaminated needles syringes
■ drug use with IV (highest frequency) or accidental
needle use
○ mother to child
■ passage through placenta, contaminated blood or If you want to learn more check out What is fate of exoduses means?
secretions during birth, breast milk — transmission rates lower with
antiretrovirals
○ premastication
■ prechewing food
● trends:
○ 33% reduction in annual new HIV cases from 2001 to 2012
○ new HIV infections among children fell 52%
○ 90% of new HIV infections are in developing countries
○ greater access to antiretrovirals led to a 30 % drop in AIDSrelated
deaths from the peak in 2005
○ U.S.: deaths through Pneumocystis carinii
■ U.S. has one of largest populations of HIVinfected in
the world
■ annual number of new infections is stable (around
50,000)
○ other areas: deaths through tuberculosis
○ 40% of adult infections are women and 15% of infections are in
individuals 1525 years of age
● mechanism:
○ retrovirus — obligate parasite that targets host cell
○ reverse transcriptase used to produce DNA from its own RNA genome
○ new DNA is incorporated in host cell genome
○ host cell treats viral DNA as its own genome
○ HIV exits cell by budding
○ HIV attacks T cells (CD4+) and compromises immune system
● AIDS:
○ acquired immunodeficiency syndrome
○ caused by human immunodeficiency virus (HIV) and is pandemicDon't forget about the age old question of How do taxes affect supply?
○ signs and symptoms:
■ HIVpositive
■ low CD4+ (helper T) cell count
■ one or more opportunistic infections (bacterial, viral,
protozoal, fungal)
■ swollen lymph nodes
■ sudden weight loss
■ Kaposi sarcoma (rare vascular cancer)
○ HIVpositive individuals progress to clinical AIDS without treatment
over an incubation period that can vary in time
■ opportunistic diseases cause death
■ anyone with AIDS will die within 4 years
● treatment and control:
○ antiretroviral drugs (ARVs)
■ highly active antiretroviral therapy (HAART) is a
combination of antiretroviral drugs that are used to control retroviruses
■ can extend years between infection and onset of AIDS,
as well as years between onset of AIDS and death
○ treatment of opportunistic infections
○ prevention measures
■ preexposure (PreP) and postexposure (PEP)
○ testing
■ antibody tests; ELISA; western blot; rapid assessment;
PCR tests
■ if positive, then test for CD4+ count, viral load, and drug
resistance
Tuberculosis (TB)
● causative agent: Mycobacterium tuberculosis
● manifestations:
○ infection (latent): 2 billion people infected with no sickness or symptoms
○ disease (active): 1/10 of infected people get the contagious form of the
infection and have symptoms; 89 million new cases worldwide per year
● transmission:
○ airborne
○ each person with active TB without treatment will infect an average of
10 to 15 people annually
● current status:
○ in the U.S. and other developed countries, TB is a reemerging disease
○ TB is the leading cause of death for individuals with HIV/AIDS
■ TB and HIV coinfection — each accelerates the other’s
progress
■ those infected by HIV are 800x more likely to develop
active TB
○ emergence of multiple drug resistance and extremely drug resistant TB
due to complacency and travel/immigration
● treatment and control:
○ 69 months of daily antibiotics, good nutrition, and rest
■ failure to take combination of drugs daily leads to drug
resistance
○ DOTS (directly observed treatment)
● prevention:
○ improved social conditions (housing, water, nutrition)
○ vaccine is controversial
■ 80% protection in children and 50% protection in adults
○ DOTS implementation
Food and WaterBorne Diseases
● water, sanitation, and hygiene (WASH):
○ basic human needs
○ prerequisite to human health and development
○ sanitation: disposal of human excreta
■ 6 F’s: feces, fields, fluid, fingers, food, flies
● waterborne diseases (WBDs):
○ caused by pathogenic microbes that can be directly spread through
contaminated water
○ most waterborne diseases cause gastrointestinal or diarrheal illness
● types of toxins:
○ food intoxication/poisoning: ingestion of bacterial toxins (with or
without the microbe)
○ foodborne infection: bacteria multiply in the intestinal tract, secrete an
enterotoxin, and may invade cells of the intestinal tract
● food intoxication/poisoning:
○ Botulism:
■ caused by deadly botulism neurotoxin of Clostridium
botulinum (g+ sporeforming bacillus)
● found in soil and improperly home
canned foods
■ treatment of antitoxin and mechanical ventilation
■ signs and symptoms: double vision, droopy eyelids,
slurred speech, muscle weakness, dry mouth, difficulty swallowing
○ Staphylococcus
■ caused by Staphylococcus aureus (g+ coccus)
● found in nasal passages
● heat stable enterotoxin
■ most common type of food poisoning
■ signs and symptoms: abdominal cramps,
nausea/vomiting/diarrhea (NVD)
■ also causes blistering from scalded skin syndrome and
toxicshock syndrome
■ Methicillinresistant Staphylococcus aureus (MRSA):
● identified in 1970s in health care
settings; leading cause of nosocomial infections in U.S.
● signs and symptoms: boils, rashes, skin
and soft tissue infections, etc.
○ necrotizing fasciitis,
also known as "flesheating bacteria”
● health careassociated MRSA:
potentially deadly strain with antibiotic resistance
● communityassociated MRSA: seen in
young, healthy; more virulent; less resistant to antibiotics
● foodborne infection:
○ Salmonellosis
■ caused by species in genus Salmonella (g bacilli)
● found in eggs, meats, seafood, fruits
vegetables
■ signs and symptoms: gastroenteritis, abdominal cramps,
NVD, fever
■ typhoid fever: in lessdeveloped countries; infection
from fecallycontaminated food or hands; transmission by flies or fomites ● organism invades cells lining small
intestine and causes ulcers and bloody stool
○ Shigellosis
■ caused by species in genus Shigella (g bacilli)
■ around 1 million annual deaths in developing countries
■ in U.S., daycares are prone to outbreaks
■ transmission: fecaloral route
■ toxins: very destructive
■ signs and symptoms: gastroenteritis, dysentery
● food and waterborne diseases
○ Cholera
■ caused by Vibrio cholerae (g curved rod)
● produces enterotoxin that promotes
secretion of fluid and electrolytes into lumen of gut
● found in brackish water
■ transmission: consumption of fecallycontaminated food
and water
■ signs and symptoms: watery diarrhea, projectile
vomiting
■ treatment of replacement of fluids, IV drugs, antibiotics
■ complications:
● severe dehydration
● hypovolemic shock
● acute renal failure
● death
● electrolyte imbalance
● hypoglycemia in children
○ Escherichia Coli
■ normally commensal organism, but can be pathogenic
■ 73,000 annual cases in U.S.
■ signs and symptoms: watery stool, vomiting, mild
abdominal pain, moderate fever, moderate to severe dehydration
■ Hemolytic Uremic Syndrome (HUS):
● hemolytic anemia (anemia caused by
destruction of red blood cells), acute kidney failure (uremia), and a low platelet count (thrombocytopenia)
○ Campylobacteriosis
■ caused by Campylobacter jejuni (g curved bacilli)
■ most frequent cause of bacterial diarrhea in U.S.
■ signs and symptoms: severe diarrhea
■ transmission: raw meat, undercooked meat,
unpasteurized milk
○ Leptospira
■ zoonotic disease in tropic areas
■ found in infected animal urine
■ signs and symptoms: flulike
■ treatment of antibiotics
○ Listeriosis (“Deli Disease”)
■ caused by Listeria monocytogenes (g+ bacillus)
● distributed worldwide in cold cuts, hot
dogs, soft cheeses, etc. (grows in refrigeration)
■ mild in healthy adults and children
○ Pseudomembranous colitis
■ caused by Clostridium difficile (g+ sporeforming
bacilli)
■ transmission: fecaloral route
■ cause of nosocomial infection
● viruses:
○ Noroviruses
■ Norwalk/Norwalklike viruses with many different
strains
■ easily transmitted and can persist in environment
■ outbreaks associated with cruise ships, food service
workers, hospitals, etc.
○ Rotaviruses
■ 200,000 emergency room visits in U.S.
■ signs and symptoms: flulike before diarrhea, fever,
cough, vomiting
● very common cause of diarrhea in U.S.
■ easily transmitted with low lethality and available
vaccines
○ Hepatitis A
■ around 1.4 million cases globally per year
■ transmission: ingestion of contaminated food and water,
direct contact
● associated with lack of safe water, poor
sanitation
■ signs and symptoms: fever, malaise, loss of appetite,
diarrhea, nausea, abdominal discomfort, darkcoloured urine and jaundice ■ no treatment, but available vaccines
● recovery usually complete without
chronic infection; rarely fatal, but can be debilitating
○ liver failure is
associated with high mortality
○ Hepatitis E
■ around 20 million cases globally per year
● over 3 million acute cases
● 56,600 hepatitis Erelated deaths
■ transmission: fecaloral route (contaminated water)
● protozoan diseases:
○ Giardiasis
■ caused by Giardia lamblia (flagellated protozoan)
■ common waterborne disease in U.S.
● 2.5 million cases per year in U.S.
● 200 million cases per year globally
■ cysts:
● spread by human, wild mammal, and
bird reservoirs
● persistent in environment
● destroy the intestinal villus
● resistant to chlorine and ID is only 10
cysts
■ transmission: swallowing cysts in contaminated water,
fecaloral route
■ signs and symptoms: abdominal pain, nonbloody
diarrhea
● not lifethreatening, but can last 26
weeks
○ Cryptosporidiosis
■ caused by Cryptosporidium parvum (nonmotile
protozoan)
● variety of mammal, bird, and reptile
reservoirs
■ transmission: oocysts enter water in fecal material and
are ingested
● oocysts resistant to chlorine and ID is
only 10 oocysts
■ signs and symptoms: severe and longlasting diarrhea (7
10 days), fever, nausea, abdominal pain
■ usually selflimiting (treatment options limited)
● lifethreatening for
immunocompromised or AIDS patients
○ Amebiasis
■ caused by Entamoeba histolytica
● occurs worldwide in water, fruits and
vegetables washed in contaminated water
■ 10% fatality rate while being one of most common
parasitic diseases
■ signs and symptoms: 90% asymptomatic or have mild
diarrhea and stomach pain
● severe dysentery causes fever, bloody
stools, and stomach pain
● amoebas can cause deep ulcers and
invade the kidneys, skin, brain, spleen, and liver (hepatitis)
○ Toxoplasmosis
■ caused by Toxoplasma gondii (nonmotile protozoan)
● domestic and feral cats are reservoir and
host
■ worldwide zoonotic disease
■ transmission: ingestion of oocysts from cat feces or
undercooked meats
■ signs and symptoms: asymptomatic, sore throat, fever,
enlarged lymph nodes — all mild
■ dangerous for pregnant women and
immunocompromised patients
Meningitis
● disease caused by inflammation of protective membranes covering brain/spinal cord (meninges)
○ two common bacterial types — Haemophilus influenzae type B (HiB has
vaccine) and Neisseria meningitidis (leading cause of meningitis)
● symptoms: headache, fever, vomiting, lethargy, neck stiffness, rash, seizures ○ can appear quickly or over several days
● complications: bloodstream infection, rash
○ requires early treatment with antibiotics
○ disfigurement, amputation, kidney failure, death still possible with
treatment
● relation to military in the past
○ now associated with college students (freshmen living in dorms)
Influenza
● respiratory disease caused by enveloped RNA viruses
○ RNA viruses enter using spikes or endocytosis and leaves by budding
(surface antigenic protein spikes)
○ disappears within 2 weeks
○ infects humans and other species (highly infectious)
● symptoms: coldlike with headache, fever, muscle pain, severe cough, congestion ● transmission: droplets or aerosol (sneezing/coughing); seasonal outbreaks (winter); crowding; fomites and other people
● strains:
○ type A: causes epidemics and pandemics; infects animals (bird flu)
○ type B: less severe; causes epidemics; no animal reservoir
○ type C: causes mild respiratory illness in humans
● antigenic change:
○ antigenic drift: type A only; major, abrupt antigenic change in spikes
with rapid evolution of new strains that people have no immunity
■ recombination of genetic material from cells infected
with different viral strains
○ antigenic shift: new variants of prevailing strains produced yearly
■ slow accumulation of mutations affect antigenicity of
spikes
● animals’ roles: avian and swine
STDs
● transmitted by sexual contact
○ public health problem due to antibiotic resistant strains and HIV/AIDS
coinfections
● syphilis
○ caused by Treponema pallidum (g spirochete)
○ can be congenital, leading to stillborns or deformities; acquired; late
○ only in humans
○ frequent coinfection with other STDs or HIV/AIDS
○ mostly MSM and aged 2039
○ no vaccine
● gonorrhea
○ caused by Neisseria gonorrhoeae (g diplococcus)
○ only in humans
○ mostly sexually active teens and young adults
○ transmitted through vaginal, anal, and oral sex
● chlamydia
○ caused by Chlamydia trachomatis (g coccobacillus; obligate
intracellular parasite)
○ most common STD
○ mostly sexually active teens and young adults
● Human Papilloma Virus (HPV)
○ DNA virus that infects epithelial cells
○ 100+ strains; persistent and has potential to cause cancer (cervical
cancer)
■ cervical cancer most common in women in 20s to 30s
○ specific control programs
■ PAP screening
■ HPV vaccination (Gardasil and Cervarix)
Cancer
● how infections can trigger cancers: around 2 million cases of cancer from infection ○ some viruses directly affect genes inside cells that control growth
○ some infections cause longterm inflammation; leads to changes in
affected/nearby cells
○ some infections suppress immune system
○ HPV
● leading cancer deaths in U.S.:
○ lung and bronchus
■ high rates of lung and bronchus cancer associated with
in tobacco consumption (2030 year delay)
○ then prostate (men) and breast (women)
■ prostate and breast cancer are more common, but lung
cancer is more deadly
● incidence versus mortality
○ cancer is second leading cause of death in U.S.
● importance of screening and stages of cancer:
○ stages of tumor development:
■ tumor begins to develop; altered cell and its descendants
grow and divide rapidly; descendants divide excessively and look abnormal
● if tumor develops, this is stage 0 (situ)
■ some cells have additional mutations that allow tumor to
invade neighboring tissues and to shed cells into blood or lymph
● tumor is malignant and escaped cells
can establish new tumors
○ best to treat before metastasis
● causes:
○ external and internal factors of metabolism act together or separately to
cause cancer
○ preventable — cigarette smoking, overweight, obesity, nutrition
■ an estimated 3040% of cancers are influenced by diet
■ foods or their components may cause, promote, or
protect against cancer
■ nutrition transition: shift in dietary consumption and
energy expenditure that coincides with economic, demographic, and
epidemiological changes
Risk Factors for Chronic Diseases
● main factors
○ dietary factors associated with 4/10 leading causes of death (coronary
heart disease, cancers, stroke, type 2 diabetes)
■ see above about preventable causes of cancer
○ saturated or trans fats
● types of obesity
○ apple vs. pear (body shape)
■ central abdominal obesity is worse than lower abdominal
obesity
● metabolic syndrome
○ combination of medical disorders or risk factors that increase risk of
cardiovascular disease and diabetes together
Emerging Infectious Diseases
● definitions
○ reemerging: new, reemerging, or drugresistant infections where human
incidence has increased in past 2 decades
■ new form or location, but existed for decades or
centuries already
○ emerging: never been recognized in humans before; difficult to establish
and rare
○ deliberately emerging: introduced (bioterrorism)
● factors involved in the emergence of infectious diseases
○ human cause — population growth, climate change, technological
advances, behavior
○ microbial evolution
○ local and global factors
○ poverty — fundamental cause of disadvantaged populations suffering
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