Viruses Flashcards
What are the common portals of entry for viruses
- respiratory tract
- GI tract
- GU tract
- placental
- eye
- skin
- transplanted organs/blood
What are the periods of infection from a virus
- incubation period (communicable toward the end)
- prodromal period (communicable)
- illness period (communicable)
- convalescent period (communicable at the beginning)
Describe zoonosis
- when an infectious disease jumps from a vertebrate animal to a human
- can spread through direct contact or through indirect contact
- covid, avian flu, ebola, etc
What are the types of viral hosts
- maintenance host: symbiosis (mosquito vector)
- link host
- amplifier host: high replication, ideally asymptomatic
What is responsible for the variability in symptoms between different people to the same virus
- different biomedical profile/immunity
- genetics & prior exposures
- difference in severity of current exposure
Describe how to diagnose a viral infection
- viral culture gold standard
- direct detection (cytopathology, electron microscopy, PCR, immunoassay)
- serology (IgG & IgM levels to check Abs)
What is the primary treatment for viral infection
- prevention (vaccines, hygiene, isolation)
- supportive care (treat sxs)
- antivirals (inhibit replication)
- immunomodulators (boost immune system)
- interferons (cytokines inhibit replication)
- virucidal agents (kill inactive virus)
Why is it hard to treat viruses (RNA viruses specifically)
- RNA viruses have high mutation rates with replication compared to DNA viruses
- Recombination: viruses can swap genetic material
- much more diverse than bacteria
- use the hosts building blocks (also hiding inside host cells)
- robust capsid
- ability to become resistant to meds that previously worked d/t mutations & recombinations
- antivirals are expensive $$$
List some viruses in the Herpesviridae family
- HSV 1 & 2
- varicella zoster
- EBV
- cytomegalovirus
- Human herpesvirus 6 & 7
- Kaposi’s sarcoma associated herpesvirus
What is the etiology of cytomegalovirus
DNA Virus
CMV: seroprevalence 40-100% of adults worldwide
- diverse spectrum of illness depending on immune status
- produces acute primary infection & latent infection (reactivation can occur any time)
Transmission through close contact, sexual, blood exposure
Describe the clinical presentation of CMV
Primary: resembles mononucleosis, significant protracted fever, fatigue
Colitis, hepatitis, encephalitis, GBS, retinitis
CMV Mono: fever predominates, less so of the LAD & tonsillitis, exudates, splenomegaly
Describe the diagnostic testing for CMV
Lymphocytosis, atypical lymphocytes
Describe the etiology of influenza
RNA virus
Seasonal epidemics
A & B cause global pandemics
Primary transition thru resp droplets, close contact, contact with contaminated surfaces
Describe the clinical presentation of influenza
Incubation 1-4 days
Sxs vary with each strain: abrupt onset fever, nonproductive cough, myalgia, sore throat, nausea, congestion, HA
Vomiting & diarrhea not common in adults
Complications: pneumonia, MI, carditis, encephalitis, GBS, myositis
Describe the diagnostic testing for influenza
Labs normal on uncomplicated flu
Confirmatory testing (rule out covid) - PCR
Describe the treatment for influenza
Oseltamivir (Tamiflu) bid x5 days shortens duration of symptoms by 1 day, reduces viral shedding, reduces severity of sxs
Describe the viral shedding of influenza
viral shedding starts in first 24hrs, peaks at day 2, rapidly declines and undetectable by day 5-10
Describe the etiology of Covid-19
RNA virus - SARS-CoV-2
Highly infectious, all ages at risk but varying risk of severity
Transmitted thru respiratory droplets, airborne, fomite, fecal-oral, vertical transmission rare
Describe the clinical presentation of covid-19
Acute respiratory syndrome
Incubation 3-14 days following exposure
If symptomatic: cough, fever, myalgia, HA, sore throat, diarrhea, loss of taste/smell, congestion
Complications; pneumonia, resp failure, cardio complications, clotting, stroke, multisystem inflammatory syndrome in children, long covid (4-9 mos)
Describe the diagnostic testing for covid-19
COVID NAAT PCR from NP or oral swab, antigen nasal swab to detect viral protein
CXR may show ground glass opacities bilaterally
Lymphopenia, elevated ALT AST, elevated LDH, elevated inflammatory markers (ESR, CRP, ferritin), abnormal coag tests (d-dimer)
Describe the etiology of monkeypox
DNA virus
Orthopoxvirus (same as smallpox)
Describe the clinical presentation of monkeypox
Rash similar to smallpox - vesicular lesions
Fever, chills, myalgias, rash at site of inoculation
Incubation 7-10 days
Describe the diagnostic testing for monkeypox
PCR swab of lesion
Describe the etiology of HIV
RNA virus
Started with “pneumocystis carinii pneumonia” in 5 men in the 80s
Transmitted through sexual intercourse, blood, vertical transmission
RF: high viremia, sexual exposure with mucosal disruption/bleeding, uncircumcised
Describe the clinical presentation of HIV
- Acute: flu like sxs in first 2-4 weeks, fever, LAD, sore throat, rash, myalgias
- Latency: chronic infection that can last for decades, relative stability with progressive CD4 cell count decline, no sxs or nonspecific fatigue, weight loss, sweats
- AIDS: CD4 count falls below 200 c/mm3, vulnerable to opportunistic infection, AIDS defining conditions present
Describe the treatment for HIV
Start ART asap (Biktarvy)
Describe the etiology of Rabies
RNA virus
Highest case fatality of any infectious dz (rare)
Canines & bats are common reservoirs, caused by lyssavirus that spreads to peripheral nerves
Describe the clinical presentation of Rabies
Incubation 1-3 mos (sometimes years)
Prodromal: mild, paresthesias around bite
Progressive encephalopathy, death
Classic encephalopathy: fever, hydrophobia, pharyngeal spasm, hyperactivity subsiding to paralysis, coma
What is the diagnostic test for rabies
PCR
Describe the treatment for rabies
Pre- exposure: High risk groups should get vaccine on days 0 and 7(rabies lab workers, bat autopsiers, spelunkers)
Post-exposure: wash wound well, rabies immunoglobulin on day 0, rabies vaccine on days 0, 3, 7, 14
Describe the etiology of Measles/Rubeola
RNA virus
Highly contagious, humans only reservoir, leading cause of mortality under 5 worldwide
Transmission: contact, airborne up to 2 hrs
Describe the clinical presentation of Measles
Incubation: 6-21 days, contagion begins day 5
Prodrome days 2-4: fever, malaise, cough, coryza, conjunctivitis, koplik spots for 12-72hrs
Exanthem: starts days 2-4 post-fever beginning on face & spreading down, LAD and high fever
Recovery: lifelong immunity
Describe the diagnostic testing for measles
IgM Ab, PCR, viral culture
Describe the treatment for measles
supportive, vitamin A
Describe the etiology of mumps
RNA virus
Transmitted by resp droplets, direct contact, fomites
Describe the clinical presentation of mumps
Incubation 16-18 days
Fever, HA, myalgia, fatigue, then 2 days later parotitis (unilateral or bilateral) for 10 days
Describe the diagnostic testing for mumps
PCR, IgM Ab
Describe the etiology of rubella
RNA virus -German Measles
Transmission through inhaled aerosolized particles
Eradicated in the US in 2004, Americas in 2015
Describe the clinical presentation of rubella
Incubation 14-18 days (contagious 1-2 weeks prior to symptoms)
Kids likely to have less sxs than adults, maculopapular rash, low grade fever, LAD
Rash starts on face, spreads to trunk & extremities, Forchheimer spots on palate, arthralgias common in adults
Describe the diagnostic testing for rubella
IgM Ab, PCR
