Viral Infection

Question 1

Herpes-simplex virus

Answer 1

• Herpes infection of the mouth + lips and in the eye is generally associated with herpes-simplex virus serotype 1 (HSV-1). Genital infection is most often associated with HSV-2 and also HSV-1.
   Treatment should start ASAP usually within 5 days of the appearance of the infection.
   Mild infection of the eye (ocular herpes), and of the lips (cold sores) is treated with a topical antiviral drug
   Severe infection, neonatal herpes or infection in immunocompromised individuals is treated with a systemic antiviral drug.

Question 2

Varicella-zoster infections

Answer 2

The Varicella-zoster virus causes chickenpox and shingles
 Neonates with chickenpox should be treated with a parenteral antiviral to reduce the risk of severe disease
 Oral therapy in children is not recommended as absorption is variable
 Chickenpox in otherwise healthy children between 1 month and 12 years is usually mild and antiviral treatment is not usually required (self-limiting)
 Chickenpox is more severe in adults + adolescents and antiviral treatment must be started within 24 hours of the onset of symptoms (e.g. rash).
 Pregnant women who develop severe chickenpox may be at risk of complications, so specialist advice must be sought.
 In shingles antiviral treatment may reduce the severity and duration of pain. Treatment should be started within 72 hours of the rash and continued for 7-10 days.

• Aciclovir is usually the drug of choice for these conditions. It is safe to use in pregnancy & taken 5 times a day.
• It is available as a cream (Zovirax) to treat cold sores, tablets as well as an eye ointment to treat herpes simplex infections of the eye.

Question 3

HIV infection

Answer 3

HIV is a virus that damages cells of the immune system. There is no cure for infection caused by the Human Immunodeficiency Virus (HIV), but a number of drugs can slow disease progression, known as Antiretrovirals (stop the virus replicating in the body).

Question 4

HIV treatment

Answer 4

• The optimum time for initiating antiretroviral treatment depends on the CD4 cell count.
• Treatment includes a combination of drugs known as ‘highly active antiretroviral therapy’
• Treatment is initiated with 2 nucleoside reverse transcriptase inhibitors (usually Tenofovir + Emtricitabine) and either a non-nucleoside reverse transcriptase inhibitor (usually Efavirenz) or a
boosted protease inhibitor (e.g. ritonavir) or an integrase inhibitor.

 Deterioration of the condition may require a change in therapy.

Question 5

HIV In pregnancy…

Answer 5

 all treatments require careful assessment by a specialist. Combination antiretroviral therapy maximises the chance of preventing transmission but may be associated with a greater risk of preterm (premature) delivery.

Question 6

Breast-feeding by HIV-positive mothers may cause

Answer 6

 HIV infection in the infant and should be avoided.

Question 7

HIV side effects

Answer 7

Osteonecrosis (death of bone tissue) has been reported in patients with advanced HIV disease or following long-term exposure to combination therapy.

Question 8

HIV infection: Pre-exposure prophylaxis

Answer 8

The risk of acquiring HIV is increased in:
• Men/transgender individuals who have had unprotected anal sex intercourse with men
• Sexual partners of people who are HIV-positive with a detectable viral load,
• HIV-negative heterosexual individuals who have unprotected intercourse with a HIV-positive person.
Emtricitabine with Tenofovir are appropriate for pre-exposure prophylaxis to reduce the risk of sexually-acquired HIV infection.

Question 9

HIV infection: Post-exposure prophylaxis

Answer 9

Prophylaxis with antiretroviral drugs may be appropriate following exposure to HIV-contaminated material as well as potential sexual exposure to HIV.

Question 10

Key facts about HIV drug treatment

Answer 10

• Ritonavir in low doses boosts the activity of protease inhibitors… increasing their plasma concentration. Protease inhibitors are associated with lipodystrophy and metabolic effects
• Psychiatric and CNS disturbances are common with Efavirenz. CNS disturbances are often self-limiting and can be minimised by taking the dose at bedtime.
• Efavirenz is also associated with raised plasma-cholesterol concentration.
• Enfuvirtide is licensed for managing infection that has failed to respond to a regimen of other antiretroviral drugs but should be used in combination with other antiretroviral’s.

Question 11

Immune reconstitution syndrome

Answer 11

Improvement in immune function as a result of antiretroviral treatment may provoke a marked inflammatory reaction against residual organisms. These reactions occur within the first few weeks or months of initiating treatment. Autoimmune disorders (e.g. graves’ disease) have also been reported.

Question 12

Influenza

Answer 12

Influenza is a highly contagious viral infection of the respiratory passages causing fever, aching and catarrh.
 Oseltamivir and Zanamivir are most effective for the treatment of influenza if started within a few hours of the first symptoms but are licensed for use up to 48 hours into a flu.
 The drugs are also licensed for post-exposure prophylaxis when influenza is circulating in the community. Oseltamivir should be given within 48 hours of exposure to influenza whilst Zanamivir should be given within 36 hours of exposure to influenza.
 The drugs are also licensed for use when vaccination does not cover the infecting strain… to prevent influenza in an epidemic.

Question 13

There is evidence that some strains of Influenza A virus

Answer 13

have reduced susceptibility to Oseltamivir but may retain susceptibility to Zanamivir.
- Thus, Zanamivir should be reserved for patients who are severely immunocompromised, or when oseltamivir cannot be used, or when resistance to oseltamivir is suspected.

• Oseltamivir can be used for children under the age of 1 for the treatment or post-exposure prophylaxis of influenza.