Infectious Disease: HIV

Question 1

Defintion

Answer 1

HIV = Human immunodeficiency virus
AIDS = Aquired Immunodeficiency Syndrome = end stage HIV infection = once the infection has affected the immune system enough to make the person susceptible to recurrent and unusual infections.
AIDS is usually referred to in the UK as last stage HIV

Question 2

Pathophysiology

Answer 2

• RNA retrovirus.
• HIV-1(MC)
• HIV-2 is rare outside West Africa.
• The virus enters and destroys the CD4 T helper cells. An initial seroconversion flu like illness occurs within a few weeks of infection. The infection is then asymptomatic until it progresses and the patient becomes immunocompromised and beings developing AIDS defining illnesses and opportunistic infections, potentially years later.

Question 3

Preventing transmission during birth

Answer 3

Mode of delivery will be determined by the mother viral load:
- Normal vaginal delivery is recommended for women with a viral load < 50 copies / ml
- Caesarean sections are considered in patients with > 50 copies copies / ml and in all women with > 400 copies / ml
- IV zidovudine should be given during the caesarean if the viral load is unknown or there are > 10000 copies / ml

Prophylaxis treatment may be given to the baby depending on the mothers viral load:
- Low risk babies, where mums viral load is < 50 copies per ml, should be given zidovudine for 4 weeks
- High risk babies, where mums viral load is > 50 copies / ml, should be given zidovudine, lamivudine and nevirapine for 4 weeks

Question 4

Breast feeding

Answer 4

HIV can be transmitted during breastfeeding, even if the mother’s viral load is undetectable. Breastfeeding is never recommended for mothers with HIV, however if the mum is adamant and the viral load is undetectable, sometimes it is attempted with close monitoring by the HIV team.

Question 5

Testing for HIV

Answer 5

• Can be done by any doctor, nurse or other trained person. - Informed consent should be documented before testing.
• It is good practice to involve both parents and child when getting consent for testing.
• Results should be given in person, by a suitably knowledgable clinician.
• Positive results may be due to maternal antibodies in children aged under 18 months. This does not necessarily mean they are HIV positive. Discuss results with an infectious disease specialist before informing parents that the child has HIV.

Two options exist for testing:

• HIV antibody screen: tests whether the immune system has created antibodies due to exposure to the HIV virus. This is the standard screening test, but it can give false positive in babies of HIV positive mums, due to maternal antibodies that cross the placenta. It can take up to 3 months for antibodies to develop after exposure to the virus.
• HIV viral load: this tests directly for viruses in the blood. This will never be falsely positive, but may come back as “undetectable” in patients on antiretroviral therapy.

Question 6

When to test for HIV

Answer 6

• Babies to HIV positive parents
• When immunodeficiency is suspected, for example where there are unusual, severe or frequent infections
• Young people who are sexually active can be offered testing if there are concerns
• Risk factors such as needle stick injuries, sexual abuse or IV drug use

Question 7

Testing in children to HIV positive parents

Answer 7

Babies to HIV positive parents are tested twice for HIV:
- HIV viral load test at 3 months. If this is negative, the child has not contracted HIV during birth and will not develop HIV unless they have further exposure.
- HIV antibody test at 24 months. This is to assess whether they have contracted HIV since their 3 month viral load, for example through breast feeding. If the 3 month test is negative and they are not breastfed, this should be negative.
Note that the antibody test can be positive in infants who do not have HIV for up to 18 months of age. This is due to maternal antibodies that have crossed the placenta during pregnancy.

Question 8

Treatment

Answer 8

Treatment needs specialist in paediatric HIV.
- Antiretroviral therapy (ART) = suppress the HIV infection
- Normal childhood vaccines, avoiding or delaying live vaccines if severely immunosuppressed.
- Prophylactic co-trimoxazole (Septrin) for children with low CD4 counts, to protect against pneumocystis jirovecii pneumonia (PCP)
- Treatment of opportunistic infections

Question 9

Aim of antiretroviral therapy

Answer 9

The aim of antiretroviral therapy (ART) is to achieve a normal CD4 count and undetectable viral load. As a general rule, when a patient has a normal CD4 and undetectable viral load on ART, treat their physical health problems (e.g. routine chest infections) as you would an HIV negative patient. When prescribing medications check for interactions with the HIV therapy.

Question 10

Paediatric HIV MDT involved in:

Answer 10

• Regular follow up to monitor growth and development
• Dietician input for nutritional support when required
• Parental education about the condition
• Disclosing the diagnosis to the child is often delayed until they are mature enough
• Psychological support
• Specific sex education in relation to HIV when appropriate