Transmission and treatment of viral infections

Question 1

How are viruses transmitted?

Answer 1

-> Respiratory through saliva and droplets
-> Cutaneous contact
-> Enteric ingestion
-> Percutaenous injection through skin
-> Arbovirus by bites from insects
-> Congenital infection
-> Perinatal infection
-> Zoonoses

Question 2

How are viruses transmitted through contact?

Answer 2

Mucosa contact of the membranes with STIs such as herpes and HIV
Cutaneous contact through skin such as human papillomavirus

Question 3

How are viruses transmitted enterically?

Answer 3

Ingestion of contaminated food from:
Norovirus: adults
Rotavirus: Children
Hepatitis A and E

Question 4

How are viruses transmitted percutaneously?

Answer 4

Penetration of the skin with :
-> through bites from insects for arboviruses
->an object for bloodborne viruses such as HIV, Hep A and B.

Question 5

What is the difference between congenital and perinatal infection?

Answer 5

Both are transmission of infection from mother to uterus.
Congenital is present at birth while perinatal occurs from utero to labour to post-birth.

Question 6

What are the congenital viral infections?

Answer 6

Cytomegalovirus
Rubella
Varicella
Parvovirus

Question 7

What are the perinatal virus?

Answer 7

HIV
Hep B
Herpes

Question 8

How are viruses transmitted zoonoses?

Answer 8

This is via animals through:
Animal bites such as rabies
Ingestion of animal meat such as hepatitis E
Insect bites eg arbovirus such as mosquitos and ticks

Question 9

What are the modes of transmisson of enveloped viruses?

Answer 9

Need to be wet to spread such as through respiratory transmission, organ transplants and injections

Question 10

What are the modes of transmission of naked viruses?

Answer 10

Spread easily because they can withstand low stomach pH and do not require a medium for transmission, generally acquired through contaminated surfaces

Question 11

What are the issues with treating viral infections?

Answer 11

Viruses hijack host cell metabolism so it is difficult to treat without harming the host. The method of replication depends on the identity of virus and its genome as well as specific enzymes and receptors.

Question 12

What are physical methods to prevent viral transmission?

Answer 12

Condoms and the insect repellent DEET

Question 13

What are passive method to prevent viral transmission?

Answer 13

Injection with antibodies.

Question 14

What is an active method to prevent viral transmission?

Answer 14

Using a vaccine with a modified antigen

Question 15

What is a non specific antiviral?

Answer 15

Cytokine Interferon, specially alpha and gamma produced during infection by fibroblasts and WBC. It causes activation of NK cells and macrophages and stimulate the host cell.

Question 16

How do interferons affect the host cell?

Answer 16

Activation of host restriction factors (anti-viral proteins) such as RNAses.

Question 17

Which antiviral medications target replcation?

Answer 17

Nucleoside analogues which cause early termination of the viral DNA chain which act against both DNA and RNA dependent viruses. It can lead to hepatic injury. This includes Aciclovir which is a treatment against herpes simplex virus and varicella foster virus.

Question 18

Which antiviral medications target viral release from host cell?

Answer 18

They can inhibit the neuroaminidase enzyme on viral surface for release from host cell. This is used to treat influenza.

Question 19

What are the targets of antivirals?

Answer 19

Replication, attachment of virus to host, release, protease inhibitor. They can also be non specific.

Question 20

What are the specialist therapies to treat HIV?

Answer 20

Combination therapies with:
Nucleotide reverse transcriptase inhibitors, integrase inhibitors, protease inhibitors and non-nucleotide reverse transcriptase inhibitors.

Question 21

What are the specialist therapies to treat Hepatitis C?

Answer 21

Combination therapies with Direct acting antivirals which are protease inhibitors, expensive

Question 22

What is the adaptive immune response to viruses?

Answer 22

Antigens are presented by MHC Class 1 to activate CD8+ T cells for lysis of virally infected cells. IgM and IgG are produced by B cells for immune defence.

Question 23

What is the role of IgM in viral response?

Answer 23

First response to viral infection and causes aggregation

Question 24

What is the role of IgG in viral response?

Answer 24

Binds to virion to prevent interaction with host cells and neutralising effect and provides anamnesis (recollection)

Question 25

What is viral latency?

Answer 25

Virus infects a cell but remains dormant but resume active replication after a period of time due to external stimuli

Question 26

Which viruses have latency?

Answer 26

Herpes, HIV, Hepatitis B and Human papillomavirus

Question 27

What is the role of interferon?

Answer 27

It is a lymphokine released by macrophages and T cells and have anti-viral effects of:
—>Increased expression of MHC CLass 1 ad 2
—>Direct inhibiton of viral replication and viral entry
—>Activation of viral killer cells like macrophages and NK cells

—>Has anti-tumour effects

** part of humoural and innate immunity.**

Question 28

WHhich type of interferon is associated with infection?

Answer 28

IFN- alpha and beta.

Question 29

When are antibodies produced in infection?

Answer 29

Late infection stage around 2-4 weeks later. This is IgM and IgG.

Question 30

What is the role of IgM in infection?

Answer 30

Aggregation, which is produced in late stage infection after 2-4 weeks.

Question 31

What is the role of IgG in infection?

Answer 31

Neutralisation of pathogen.
Anamnesis (MEMORY)