Virology Flashcards
What virus contains its own viral polymerase?
adenovirus erythrovirus B19 hepatitis B virus hepatitis C virus herpes simplex virus
HBV
In this question, hepatitis C genetic material is positive-sense RNA, which can be used directly by the host enzymes, as it is equivalent genetic material to mRNA.
Most DNA viruses can use host enzymes for replication, negating the need for them to provide their own viral polymerase. Adenovirus, erythrovirus B19, and herpes simplex virus are all DNA viruses.
The exceptions to above include DNA viruses hepatitis B, and poxviridae (e.g smallpox, molluscum contagiosum). Hepatitis B is an unusual DNA virus, and is classified as Baltimore group VII. It has a unique viral polymerase which exhibits both DNA-dependent DNA polymerase, and RNA-dependent DNA polymerase (reverse transcriptase).
What virus has an icosahedral nucleocapsid?
Ebola HIV influenza Lassa rabies
HIV
What virus is most likely to survive in the environment for a prolonged period of time due to its viral structure?
cytomegalovirus hepatitis B virus hepatitis C virus norovirus influenza A
Norovirus
CMV, hepatitis B, hepatitis C, and Influenza A are all examples of enveloped viruses. The envelope is typically made from host phospholipids, and viral glycoproteins. You may think the envelope would protect the viral capsid, and allow it to survive in the environment. However, the envelope is actually susceptible to the environment which includes - temperature, pH, desiccation, and chemicals. Once the envelope is breached, the virus loses its functional receptors (viral glycoproteins), which means it is no longer able to infect cells.
Non-enveloped (naked) virus examples include coxsackieviruses, polioviruse, rotavirus, and norovirus. They can survive in environment for extended periods. Norovirus may persist in the environment for at least 12 days (see CDC Guidance on norovirus, and a 2015 review on norovirus by Robilotti et al here.). Because they lack a lipid envelope, they are less affected by environmental conditions, thus enabling them to persist longer.
You are contacted by a neonatal nurse. She is 12 weeks pregnant and is responsible for nursing a baby with congenital CMV. Whilst waiting for her CMV serology to be tested, she asks whether she can continue caring for the baby.
What activity carries the highest risk of her acquiring CMV?
changing the baby's nappies close skin contact with the baby feeding the baby with the mother's expressed breast milk performing eye care venepuncture
changing the baby’s nappies
Many pregnant women will be seropositive, however this nurse does not know her status as yet. Ideally she should not nurse a child with congenital CMV as they excrete virus at high levels for a prolonged time. CMV is present at high levels in the urine so changing nappies is the highest risk activity.
Through various media sources, it becomes apparent to you that there are an unusual number of outbreaks of respiratory disease in clusters around the world. Cases were of respiratory illness ranging from relatively mild illness that did not require hospitalization to severe illness requiring intensive care and mechanical ventilation. Investigations are underway to work out what the responsible agent is, and what the epidemiological links are.
What virus is associated primarily with respiratory disease?
enterovirus 68 human herpes virus 6 Machupo virus Nipah virus Ross river virus
enterovirus 68
Enteroviruses are a large group of viruses belonging to the Picornaviridae family. They are responsible for a wide range of clinical syndromes including polio. They can be responsible for aseptic meningitis, encephalitis, paralysis, herpangina, pleurodynia, myopericarditis, respiratory disease and hand, foot and mouth disease. Enterovirus 71, which can cause severe neurological disease, usually causes hand foot and mouth disease with a non-itchy rash on the palms and soles and painful ulcers in the mouth.
A neonatal doctor contacts you for advice after reviewing results for a baby who has been born at full term and is now healthy. During the pregnancy, an amniotic band was noted on ultrasound scan and subsequently investigations for intrauterine infection were performed. The mother was well throughout the pregnancy. She had a history of cold sores since childhood, and had never had any genital lesions.
Maternal herpes simplex virus 1 IgG detected
Maternal herpes simplex virus 2 IgG not detected
The neonatal doctor would like to know the significance of these results and whether the mother and baby can be discharged home.
What is the most appropriate action?
admit infant for observation
give prophylactic aciclovir to the infant
reassurance only
screen infant with surface swabs and blood for HSV PCR
warn and inform of low risk of neonatal HSV from postnatal transmission
warn and inform of low risk of neonatal HSV from postnatal transmission
Advise to avoid oral contact
As it is HSV from mouth swab, that is lower risk than genital lesion. Also, recurrent HSV suggests good IgG response, which will transfer to baby.
