Human Diseases Flashcards
Airborne Viruses
Chickenpox, Shingles, Influenza, Measles, Mumps, Respiratory Syncytial Virus, Rubella, SARS, Smallpox.
Chickenpox
(Varicella-Zoster Virus). DNA virus.
Airborne; human reservoir
Shingles
(Herpes Zoster). Reactivated chickenpox.
Treatment: acyclovir, antivirals
Influenza
RNA virus.
Airborne; various animal reservoirs.
Secondary infections common (pneumonia)
Treatment: inactivated virus vaccine, symptomatic therapy
Antigenicity constantly changing due to antigenic drift (accumulation of mutations in a geographic area) and shift (reassortment of genomes when two strains infect the same cell).
Influenza Subtypes
Hemagglutinin (HA) and Neuraminidase (NA). Each is a membrane surface protein that function in viral attachment and virulence.
Measles
(Rubeola). RNA Virus.
Airborne; causes subacute sclerosing panencephalitis which is a progressive degeneration of the CNS.
Treatment: symptomatic therapy, MMR vaccine
Mumps
RNA virus.
Airborne; can cause meningitis and orchitis (testes inflamm.)
Treatment: symptomatic therapy, MMR vaccine
Respiratory Syncytial Virus
RNA (-) virus.
Airborne or contact; dangerous for children; causes cold-like symptoms which may progress into bronchitis/pneumonia.
Treatment: inhaled ribavirin, RSV immune-globulin
Rubella
(German Measles). Enveloped RNA virus.
Airborne; causes mild rash; congenital version is bad for pregnancy, can lead to fetal death.
Treatment: MMR vaccine
Severe Acute Respiratory Syndrome
(SARS-associated coronavirus).
Airborne; can be fatal, dry cough, often pneumonia.
Treatment: none approved
Smallpox
(Variola). Linear dsDNA virus.
Airborne or contact; causes rash and high fever.
Smallpox Erradication
Made possible because:
Humans are only reservoir, there are no asymptomatic carriers, the disease has obvious clinical features, and has a short infectivity period
Arthropod-borne Viruses
From blood-sucking arthropods. West Nile Fever.
West Nile Fever
(Encephalitis). RNA virus.
Arthropod-borne; causes fever, rash, possible encephalitis (inflamed brain).
Direct Contact Viruses
Via touching, sex, etc. AIDS/HIV, Cold Sores, Common Cold, Genital Herpes, Mononucleosis, Viral Hepatitis, Warts, Viral Gastroenteritis, Poliomyelitis.
HIV
RNA retrovirus.
Direct contact; can develop into AIDS (last stage) and compromise the host immune system. Course of disease is monitored by Th cell count (below 200/uL is AIDS)
Treatment: No cure, drug cocktails often used
HIV Life Cycle
Virion has a protein spike (gp120) that attaches to CD4+ cells. Reverse transcriptase then transcribes the RNA into dsDNA which is then integrated into the host as a provirus. Can remain latent or direct synthesis of new viruses that are released via budding.
HIV Stages
Acute: few weeks after infection; mild illness; virus replicates throughout body.
Asymptomatic (latent): 6 months-10years; virus is latent, but still replicating.
Chronic Symptomatic: can last for years, virus still replicating, CD4+ count drops significantly, opportunistic pathogens emerge.
AIDS: immune system no longer viable, CD4+ count below 200/uL or 14%.
HIV Drugs
Nucleoside RT Inhibitors (AZT)
Nonnucleoside RT Inhibitors
Protease Inhibitors
Fusion Inhibitors (prevent HIV entry into cells)
Berlin Patient
Only person ever cured of HIV. Received a stem cell transplant from a donor with the CCR5 delta32 mutation (CCR5 is a co-receptor for HIV).
Cold Sores
(Herpes simplex virus 1, HSV-1). Enveloped dsDNA virus.
Direct contact; infect epithelium around mouth, can be active or latent.
Treatment: acyclovir, antivirals, no vaccine
Common Cold
(Rhinoviruses). ssRNA viruses.
Airborne or direct contact
Treatment: symptomatic therapy
Genital Herpes
(HSV-2). Linear, enveloped dsDNA virus.
Direct contact; common STD, can be active or latent
Treatment: acyclovir, antivirals, no vaccine
Mononucleosis
(Epstein-Barr virus, Herpes). Enveloped dsDNA virus.
Direct contact; infects B cells and causes enlarged lymph nodes, flu-like symptoms; lasts 1-6 weeks.
Treatment: symptomatic therapy
Viral Hepatitis
A, B, C, D, and E. Inflammation of the liver.
Hepatitis A
(HAV). Linear RNA (+) virus.
Direct contact; spread by fecal-oral contamination; causes GI infection, jaundice.
Treatment: Killed HAV vaccine, hygiene
Hepatitis B
(HBV). dsDNA virus.
Direct contact, can pass through placenta and breast milk; Dane particle is virion; can cause jaundice, chronic infection can lead to liver cancer.
Treatment: passive immunotherapy, HBV vaccine
Hepatitis C
(HCV). RNA virus.
Direct contact via blood, fecal-oral, mother-fetus, or organ transplant; commonly leads to chronic infection, leading cause of liver transplant in US.
Treatment: combo therapy of Ribovirin and Interferon-alpha
Hepatitis D
(HDV, Delta agent). RNA virus.
Direct contact; dependent on HBV to provide envelope protein (HbsAG); causes severe acute and chronic infections in those with HBV.
Hepatitis E
(HEV). RNA virus.
Direct contact via fecal-oral route; high mortality in pregnant women, common in developing countries.
Warts
(Verrucae, human papillomavirus). DNA virus.
Direct contact; infect epithelium and mucous membranes; four types- genital warts is a major cause of cervical cancer.
Treatment: physical destruction, podophyllum, IFN-alpha
Viral Gastroenteritis
GI inflammation and diarrhea caused by rotavirus, adenovirus, astrovirus, or norovirus. Leading cause of childhood death in developing countries.
Polio
(Poliomyelitis). RNA (+) enterovirus.
Direct contact; usually asymptomatic or mild, but can enter CNS and cause paralysis.
Treatment: vaccine
Zoonotic Viruses
Viruses with animal reservoirs that are transmitted to humans. Ebola, Marburg, Hantavirus, Rabies, Lassa fever, Nipah virus.
Ebola Hemorrhagic Fever
(Filoviridae). ssRNA virus (-).
Zoonotic or direct contact; 80% fatal; causes internal hemorrhaging.
Treatment: none, supportive therapy
Marburg Hemorrhagic Fever
(Filoviridae). RNA virus.
Zoonotic; causes multi-organ dysfunction
Treatment: none
Hantavirus Pulmonary Syndrome
(HPS). ssRNA virus (-).
Zoonotic, fecal-oral inhalation from rodents
Treatment: none
Rabies
RNA virus (-). Zoonotic, from saliva or fluids of infected animals; highly neurotropic, can ascend through CNS into brain and cause fatal encephalitis and paralysis. Treatment: pre- and post-exposure vaccination
Prion Diseases
Transmissible spongiform encephalopathies that cause fatal neurodegenerative disorders that may remain clinically silent for months. Includes: Kuru, Bovine spongiform encephalopathy.
Airborne Bacterial Diseases
Meningitis, Tuberculosis, Streptococcus, Staphylococcus.
Meningitis
Inflammation of brain or spinal cord, many different causes. Bacterial cause identified by Gram (-) stain of CSF, from Strep. pneumoniae, Neisseria meningitidis (college), and Haemophilus influenza.
Tuberculosis
(Mycobacterium tuberculosis, Mtb).
Airborne or zoonotic; 1/3 of humans infected; develops slowly, kills lung macrophages during attack and forms tubercles; intracellular bacteria.
Treatment: antimicrobial therapy (if non-resistant strains)
Mtb Virulence Factors
Mycolic acid and others kill eukaryotic cells and protect Mtb from lysozyme and lysis. Can survive phagocytosis inhibiting phag-lysosome fusion, diffusion of lysosomal enzymes, and resisting oxidative killing.
Tubercles
Complexes of bacteria, macrophages, proteins, and T cells form during a hypersensitivity reaction to Mtb. Ghon complexes (calcified lesions) eventually form which are visible on X-rays.
Streptococcus pyogenes
(Group A Streptococci, GAS). Gram (+)
Invasive: causes necrotizing fasciitis (flesh eating), myositis (inflammation/destruction of muscle), and toxic shock-like syndrome (exotoxin that causes drop in blood pressure and organ failure).
Streptococcal Pharyngitis
(Group A, noninvasive, Strep Throat). beta-hemolytic.
Direct Contact, via saliva, mucous; infection in throat or tonsils that can cause Rheumatic fever and Glomerulonephritis.
Streptococcal Group B
(Streptococcus agalactiae). beta hemolytic. Gram (+).
Direct contact; common cause of neonatal and newborn diseases (sepsis, meningitis, pneumonia).
Peptic Ulcer Disease/ Gastritis
(Helicobacter pylori). Gram (-).
Can cause ulcers and stomach cancers; produces urease (hydrolyzes ammonia, increasing pH), releases enzymes and toxins (proteases, phospholipases, and cytotoxins) that damage epithelial mucosal cells. Nobel prize for Marshall/Warren.
Staphylococcal Diseases
Caused by Gram (+) Staphylococci. Facultative anaerobes, catalase positive. Part of normal flora.
Staph. aureus
Coagulase positive, pathogenic. Can infect skin and organs, often nonsocomial (hospital-acquired). MRSA is resistant to beta-lactams and can be community acquired (CA).
Staph. epidermidis
Coagulase negative, less pathogenic. Nonsocomial opportunist.
Staphylococcal Virulence Factors
Invasiveness enzymes
Protein A (antiphagocytic)
Coagulase (produces fibrin clots to protect against phagocytosis)
Panton-Valentine leukocidin (inhibits phagocytosis, kills granulocytes)
Exotoxins (enterotoxins A,B,C,D,E responsible for food poisoning; Toxic Shock Syndrome Toxin 1 (TSST-1) superantigen)
Toxic Shock Syndrome
Caused by TSST-1 superantigen of S. aureus. TSST-1 binds to MHC Class 2 and TCR, leading to T cell over expression and circulatory collapse/shock.
Tetanus
(Clostridium tetani). Gram (+), anaerobic spore-former.
Transmitted through skin wounds from endospores in soil, dust, hospitals, and feces; produces tetanospasmin that causes muscle spasms and tetanolysin that hemolyzes.
Begins with cramping, then progresses to convulsions and respiratory spasms that may be fatal.
Treatment: antibiotics, DPT vaccine, prophylactic antitoxin
Tetanus Toxin
Blocks release of inhibitory neurotransmitters between motor neurons, causing constant muscle contraction.
Food/Water Borne Bacterial Diseases
Botulism, Cholera, E. coli, Salmonellosis, Typhoid fever.
Botulism
(Clostridium botulinum). Gram (+), obligate anaerobe, endospore forming.
Common from home canned-food.
Botulinum Toxin
Neurotoxin that binds to synapses of motor neurons and caused flaccid paralyses (opp. of tetanus), floppy baby.
Cholera
(Vibrio cholerae).
Oral-fecal transmission, dirty water, uncooked seafood; causes “rice-water stools” (severe diarrhea); bacteria produces an enterotoxin that binds intestinal cells and reverses intestinal absorption. Prevented with water sanitation and thorough cooking.
Cholera Toxin
AB toxin: B part binds to intestinal epithelial cells; A part enters, activates adenylate cyclase; cAMP is produced which stimulates secretion of Na+ and Cl-, causing water to follow out of cell.
E. coli Gastroenteritis
(Traveler’s diarrhea). Six major pathogenic strains: enterotoxigenic, enteroinvasive, enteropathogenic, enterohemorrhagic, enteroaggregative, and diffusely adhering.
Enterotoxigenic E. coli
Produces enterotoxins responsible for diarrhea, ST (heat-stable) and LT (heat-labile), which cause secretion of electrolytes and water out of intestinal cells.
Enteroinvasive E. coli
Reproduces within intestinal cells and may produce a cytotoxin and enterotoxin to cause diarrhea.
Enteropathogenic E. coli
Attach to cells via adhesins and delivers virulence proteins by a Type III secretion system. Also causes lesion on intestinal cells by destruction of microvilli.
Enterohemorrhagic E. coli
Causes hemorrhagic colitis and effacing lesions. Releases shiga-like toxins (Stx-1 and Stx-2).
Enteroaggregative E. coli
Forms clumps that adhere to intestinal cells in a “stacked brick” appearance. Cause prolonged diarrhea in kids.
Diffusely Adhering E. coli
Adheres in a uniform pattern to intestinal cells. More common in malnourished, immune-compromised children.
Salmonellosis
Gram (-), non-spore forming.
Food/Water borne via produce and water; caused by >2000 Salmonella serovars (types); bacteria in intestines produce enterotoxin and cytotoxin diarrhea, cramps, fever, nausea.
Treatment: fluids and electrolytes, thorough cooking.
Typhoid Fever
(Salmonella enterica). Gram (-).
Direct contact or fecal-oral contamination; bacteria can spread from intestines to other tissues and organs.
Treatment: antibiotics, vaccine, water purification, thorough cooking.
Antibiotic-Associated Colitis
(Clostridium difficile). Anaerobic, spore-forming.
Opportunistic bacterium, pathogenic after excessive antibiotic use; pseudomembranous colitis is a collection of cells that obstructs the intestine; can lead to a toxic megacolon and tissue death. Most common cause of diarrhea in hospitals.
Treatment: antibiotics, fecal transplant
Pathogenic Fungi
Eukaryotic saprophytes. Routes of infection: direct contact (superficial, cutaneous, subcutaneous), systemic (moved to visceral tissue), and opportunistic mycoses.
Pathogenic Protists
Protozoa are single-celled eukaryotic chemoorganotrophs. Transmitted via food/water vehicles, direct contact, and arthropod vectors.
Dimorphic Fungi
Two morphologies (yeast and mold), often temperature dependent - Yeast (37C), Mold (25C). Often grow in soil as a mold, in bodies as a yeast.
Coccidioidomycosis
(Coccidioides immitis). Dimorphic fungi.
Airborne, from dust; arthroconidia are inhaled, convert into large spherules in body. Valley fever, San Joaquin fever, Desert Rheumatism
Cryptococcosis
(Cryptococcus neoformans). Yeast.
Airborne, inhalation of dried pigeon crap; systemic mycosis that can lead to meningitis or pneumonia.
Histoplasmosis
(Histoplasma capsulatum). Dimorphic.
Airborne, mitoconidia are inhaled, converts to yeast in body; common lung disease that causes flu-like illness.
Treatment: soil decontamination, protective clothing
Malaria
(Plasmodium). Plasmodial protist.
Arthropod borne via female mosquitos; causes chills, fever, anemia; diagnosed via RBC staining.
Treatment: antimalarial drugs, netting, insecticide, new vaccine
Plasmodial Protist Life Cycle
Sporozoite injected with mosquito bite; replicates as merozoite in hepatic cells; releases, enters into erythrocytes, and replicates; lyses erythrocytes
Trypanosomiasis
Caused by trypanosomes. Flagellated protists. alters protein coats (antigens) and evades immune response.
African Trypanosomiasis
Transmitted via tsetse flies; leads to lethargy (sleeping sickness) and death in 1-3 years.
Treatment: drug therapy, no vaccine
Chagas’ Disease
Trypanosomiasis transmitted via kissing bug that sucks blood then craps in wound. Trypanosome is in feces.
Acute: rapid onset, trypanosome moves through blood to cells and becomes amastigote, replicates.
Chronic: amastigotes reach heart and GI cells, replicate and cause heart disease due to parasitized cells.
Treatment: vaccines not efective due to antigenic variation
Superficial Mycoses
Piedras: infections of hair shaft
Tineas: Infections of outer layers of skin, nails, hair
Most common in tropics
Cutaneous Mycoses
Dermatomycoses, ringworm, and tineas; most common fungal diseases; diagnosed via skin biopsies and cultures on glucose agar.
Trichmoniasis
(Trichomonas vaginalis). Flagellated protist.
Common STD; discharge from vagina, leukocyte accumulation at infection, asymptomatic in men.
Toxoplasmosis
(Toxoplasma gondii). Nonmotile protist.
Rodent, cat reservoir, fecal-oral transmission; mostly asymptomatic or mono-like, encephalitis in immunocompromised hosts, tachyzoites can cross placenta and infect fetus (bad for pregnant women)
Treatment: antiparasites, cat handling practice
Candidiasis
(Candida albicans). Dimorphic fungi.
Opportunistic, in normal flora; can be virulent with disruption of microbiota; infects skin and mucous membranes.
Oropharyngeal Candidiasis
(Thrush). Common in newborns, denture wearers, steroid takers.
Paronychia and Onychomycosis
Candida infections of subcutaneous tissue of finger and nails.
Intertriginous Candidiasis
Infections of groin, skin folds.
Napkin Candidiasis
(Diaper). Infects infants with dirty diapers.
Balanitis
Candida infection of uncircumcised penis, transmitted via sex.
Pneumocystis Pneumonia
(Pneumocystis jiroveci). Fungi.
PCP occurs in immunocompromised hosts; localized to lungs; common in AIDS patients.
