Viral Infections Flashcards
Define ‘pyrexia or fever of unknown origin’
Temperature >38.3 on >1 reading
No diagnosis after 3 weeks of community or 1 week of hospital tests
Define ‘acute undifferentiated febrile illness’
Temperature >38.0 with no organ focus
<2 weeks duration
Define ‘fever and febrile illness’
Temperature >38.0
Name some occult infections responsible for fevers of unknown origin
Endocarditis
Liver abscess
UTI
LRTI
Describe the lifecycle of viruses
- Virion (containing capsid, DNA and envelope) adsorption and fusion with cell membrane
- Penetration into cell and uncoating of virus from envelope
- DNA enters the host cell’s nuclear membrane
- Transcription of viral DNA
- Transcription produces messenger RNA which produces the proteins necessary to build the next capsids and replicate viral DNA
- New virus particles are assembled (maturation) in the cytoplasm
- Viruses bud out of the host cell, taking with it some of the cell’s membrane
Define acute viral infection
Primary infection, usually followed by clearance and immunity
Define latent viral infection
Primary infection followed by restricted viral gene expression
Define chronic/persistent viral infection
Primary infection followed by persistent viral replication
Name some common viruses causing meningitis/encephalitis
JC virus
Measles
Arbovirus
Rabies
Name some viruses causing the common cold
Rhinovirus
Parainfluenza virus
Respiratory syncitial virus
Name some viruses that cause pharyngitis
Adenovirus
Epstein-Barr virus
Cytomegalovirus
Name some viruses causing hepatitis
Hepatisis A, B, C, D and E
Name some viruses causing skin infections
- Varicella zoster virus
- Human herpes virus 6
- Human papilloma virus
- Smallpox
- Molluscum contagiosum
- Parvovirus B19
- Rubella
- Measles
- Coxsackie A
Name some sexually transmitted viruses
Herpes simplex virus 2
Human papilloma virus
HIV
Name a virus that can cause pancreatitis and cardiovascular infections
Coxsackie B virus
Name some viruses that cause pneumonia
Influenza virus A and B
Respiratory syncitial virus
Parainfluenza virus
Name some viruses that cause gastroenteritis
Adenovirus
Rotavirus
Norovirus
Astrovirus
Coronavirus
Name some viruses that cause myelitis
Poliovirus
HTLV-1
What are the positive and negatives of using serology to diagnose viruses?
Pros:
- Positive in chronic, past and latent infections
Cons:
- Sometimes difficult to interpret
- Negative in early stages of infection
What are the positive and negatives of using PCR to diagnose viruses?
Pros:
- Positive in the early stages of acute infection
- Highly sensitive and specific
- Can identify anti-viral resistance genes
Cons:
- Negative in latent and past infection
What does the human papilloma virus cause?
Warts
Cervical cancer
Name viruses from the herpes family
Herpes simplex viruses 1 and 2
Varicella zoster virus
Epstein-Barr virus
Cytomegalovirus
What can the HSV-1 and 2 viruses cause?
Usually perioral or genital infections→ localised painful vesicles
Rarely:
- Encephalitis
- Bell’s palsy (recurrence in facial nerve)
What can the varicella zoster virus cause?
Usually ‘chicken pox’ → fever and vesicles in centripetal distribution
Occasionally:
- VZV meningitis
- Ramsey Hunt syndrome (recurrence in facial nerve)
What can the herpes zoster virus cause?
Shingles
Can reoccur in the trigeminal nerves: trigeminal herpes zoster
What are the main features of the Epstein-Barr virus?
Causes glandular fever
Transmitted through oral and genital secretions
Targets B-lymphocytes and becomes latent
Infects 50% of children by age 5 and 90% of adults
Symptoms more severe with increasing age: pharyngitis, lymphadenopathy, splenomegaly, fever, hepatitis
Reactivation occurs, usually asymptomatic
Associated with certain cancers (e.g. lymphoma, nasopharyngeal carcinomas) and MS
What are the main features of cytomegalovirus?
Causes glandular fever
Transmitted by oral and genital secretions, breast milk, urine, blood and congenital.
Infection occurs in 50% of adults
Symptoms more severe with increasing age: fever, pharyngitis, lymphadenopathy, splenomegaly, hepatitis
Congenital infection causes hearing loss, seizures, visual loss, microcephaly
Reactivation occurs at random or when immunocompromised; causes retinitis, pneumonia, hepatitis, colitis
