Viruses Flashcards
Type: Virulence: Pathogenesis Clinical: Treatment:
Polio
T: Enterovirus,
Picornavirus (unenveloped positive sense ssRNA virus); human reservoir
V: Infects and spreads through CNS;
Survives acidic GI tract;
Inhibits host protein translation;
Inhibits transport and release of proinflammatory cytokines;
Inhibits host cell transcription
P: Enters body via GI tract;
Primary replication in lymph nodes in small intestine;
Hematogenous spread and secondary replication in liver and spleen;
Spread to CNS, infects brain
C: GI - fever, V/D
Meningitis, encephalitis - headache, fever (1% of infections spread to CNS);
T; Paralytic poliomyelitis - acute paralysis
Inactivated injected or oral attenuated vaccine; Pleconaril
Rotavirus
Type:
Reovirus
(dsRNA, unenveloped, acid-resistant) human res.
Virulence:Nonstructural protein (NSP4) that has enterotoxin-like properties; acid resistance
P: Multiplies in intestinal mucosa after ingestion; symptoms start ~48 hours after ingestion
C: Intense diarrhea, often preceded by vomiting; fever; last several days to a week; can cause severe dehydration
T: Vaccine recommended for young; fluid/ electrolyte balance
Hepatitis A
T: Picornavirus (positive sense ssRNA, unenveloped); human reservoir
V:Unknown
P: Transmitted via fecal/oral route; replicates in gut; ~50% of people have flu-like illness; if insufficient antibodies, it invades the blood and spread to the liver causing acute hepatitis (not chronic); <1% have fatal hepatitis
C: Flu-like illness initially, can progress to acute hepatitis, can be fatal
T: Hygiene, vaccine, HAV Ig for passive immunity
Hantavirus
T; Bunyavirus (negative sense ssRNA in 3 distinct molecules, enveloped); deer mouse reservoir
V: Two envelope glycoproteins that determine host range;
Aggressively multiplies in host, is excreted, and is able to survive dehydration From deer mice, humans breathe in aerosolized form, invades, replicates, and spreads to other organs (heart, gut, liver, CNS); can lead to hemorrhagic fever, possibly involving renal syndrome, or pulmonary syndrome
C: Fever, headache, malaise, GI symptoms, hemorrhagic disease that can be complicated by renal failure; pts with HPS present with thrombocytopenia, leukocytosis T: Administration of IV fluid, kidney dialysis if renal failure occurs
Rabies
T: Rhabdovirus (negative sense ssRNA, enveloped)
V: Neuronal tropism;
Targets acetylcholine receptors;
Maintenance via asymptomatic persistence in some hosts
P: Animal reservoir, transmission by bite; spreads up peripheral nerves to CNS, then migrates down nerves to organs and glands; can cause cardiac/ respiratory failure, encephalitis, leading to death
C: Abnormal sensation at bite site; confusion, lethargy, paresis, increased salivation; hydrophobia in advanced rabies
T: PEP with rabies Ig; if exhibiting clinical symptom is too late to treat; immunization for ppl at high risk
Variola Major (small pox)
T: Pox virus, (dsDNA, enveloped)
V: Contraindications for vaccine - immunodeficient, chronic eczema, pregnancy; Adverse reactions - eczema vaccinatum, progressive vaccinia, encephalitis
P: Transmission from contact with infected people, fomites, droplets/aerosols
C: Rash - maculopapular, vesicles, pustules, crusts, scarring; centrifugal spread of lesions
T: Vaccine; but has been eradicated;
Vaccine has contraindications and adverse reactions; Cidofovir
Viral Hemorrhagic Fevers
T: Filoviruses and Arenaviruses (negative sense ssRNA, enveloped) Highly contagious, extremely virulent
V: Filoviruses - Ebola, Marburg
Arenaviruses - Lassa, Machupo
P: Transmitted by aerosol, urine, feces, fomites, saliva, or ocular exposures from animal, or contact with blood/bodily fluids of an infected person
C: High fever, generalized vascular damage, shock
T: Ribavirin for arenaviruses
Adenovirus
T: Adenovirus (dsDNA, unenveloped); serotype determines its cellular receptor
V: Genes encode for mRNA and hijack the normal growth resources for viral replication; evades immune system by blocking cell signaling (MHC synthesis, interferons, apoptosis); destroys cells
P: Transmission from human to human; virus binds to local epithelial/lymphoid cells, enters, and lyses cells leading to viremia and dissemination;
C: Pharyngoconjunctival fever, enteritis, pneumonia, keratoconjunctivitis
T: Supportive care; limit contacts for prevention; vaccine available for those at high risk (military)
Hepatitis B
T: Hepadnavirus (incomplete dsDNA, uses viral RT)
V: Number of different antigens (surface, core); able to establish chronic infection; surface antigen can act as immune decoy; HBx protein may play a role in the development of carcinoma
P: Entry via blood, mucosa contact; enters bloodstream, replicates in liver, damages hepatocytes; infection can be cleared or become chronic leading to cirrhosis and possibly hepatocellular carcinoma
C: Elevation of liver enzymes (ALT, AST), jaundice
T: Interferon, Lamivudine, Tenofovir; liver transplant, vaccine available (against surface antigen); HBIg for acute infx
Hepatitis D
T: Defective RNA virus (requires HBV to replicate)
V:Direct viral cytopathic effects; other factors similar to HBV
P: Must co-infect with HBV; more severe than HBV alone
C: Acute and chronic hepatitis; jaundice, elevated liver enzymes
T: HBV vaccine; IFN-a, liver transplant if severe
Hepatitis C
T: Flavivirus (positive sense ssRNA, enveloped)
V; High mutation rate/variability of genome;
Protease blocks immune activation of infected cells
P: Entry into blood, infects liver cells, causes inflammation leading to possibly chronic disease, cirrhosis, hepatocellular carcinoma
C: 10-20% develop chronic hepatitis (cirrhosis and carcinoma risks)
T: Liver transplantation; PegIFN, ribavirin, protease inhibs
Epstein-Barr Virus
T: Herpesvirus (dsDNA, enveloped)
V: Causes immortalization of B cells, causing PTLD and possibly lymphoma; antigen not presentable by MHCI, so evades immune detection; long term latency
P: Infects B cells and nasopharyngeal cells (CD21 receptor); primary replication in pharyngeal epithelium or tonsillar B cells; spread to lymph nodes and spleen; PTLD is growth of latently infected B cells
C: Acute infx can be asymptomatic or have fever, lymphadenopathy; chronic infx associated w/ Burkitt’s lymphoma, nasopharyngeal carcinoma, lymphoma, post-transplant lymphoproliferative disease
T: No vaccine; no treatment for acute disease; PTLD-decrease immunosuppression; acyclovir/ ganciclovir during replicative cycle; immune therapy
Influenza virus
T: Orthomyxovirus (negative sense ssRNA, enveloped, segmented - 8 pieces)
V: Hemagglutinin - allows release of viral RNA inside of host cell;
Neuraminidase - allows for release of new viral particles for infection of new cells; Segmented genome allows for reassortment, new virulence (antigenic shift)
P: Infects respiratory epithelium, kills cells; HA is essential for binding to cells and causing fusion, allowing entry of virus into cell for viral replication; NA prevents viral aggregation and aids in releasing new viral particles
C: Uncomplicated - fever, chills, headache, myalgia, malaise for ~3 days, recovery up to 2 weeks;
Complicated - secondary bacterial pneumonia from S. pneumoniae or H. flu, croup, exacerbation of chronic illnesses
T: Oseltamivir (Tamiflu) is primary drug given
Amantadine and Rimantadine have emerging resistance;
Vaccinate yearly
HIV
T: Retrovirus (positive sense ssRNA, enveloped)
V: High rate of mutation for evasion of immune system; Forms permanent reservoirs in tissues
P: Infects CD4 helper T cells, kills them by lysis; CD8 T cells respond and suppress virus to an extent, but can’t clear it; have persistent immune activation which increases target cell availability, promotes viral replication, and increases apoptosis; destroys architecture of lymph nodes - T cells can’t keep up
C: Acute retroviral syndrome - mimics infectious mononucleosis
Chronic - opportunistic infections - many
T: Combinations of NRTIs, NNRTIs, protease inhibitors, fusion inhibitors, integrase inhibitors, and entry inhibitors
Herpes HSV
T: Herpesvirus (dsDNA, enveloped)
V: Humans are sole reservoir;
Viral DNA synthesis to maintain nucleotide pools in quiescent cells; turns off host cell protein synthesis and blocks apoptosis; blocks complement, antibody, and antigen recognition
Tzanck smear stain for detection (also detects VZV)
P: Spread by intimate or direct contact; attaches to heparan sulfate and HveA receptors on host cells, fusion with cell, transcription of viral genome, DNA replication occurs in nucleus, virion release results in cell death (lytic); can have latent stage where Latency- Associated Transcript (LAT) is expressed, no overt disease
C: Vesicular lesions (genital or orofacial); severity varies with serotype; can spread to CNS causing encephalitis; herpetic stromal keratitis - infects cornea causing blindness; more complications in the immunocompromised
T: Acyclovir to decrease severity and duration; incurable and persists for life; C-section to prevent infx of baby; Abreva (blocks viral entry)
