Glossary

compensatory mutation – this refer to an additional mutation, usually in the context of the fitness of a virus. For example, the mutations that stop a drug form working often stop the virus from reproducing as well. Additional mutations that return the virus to it’s former fitness are called compensatory mutations. They compensate for the reduced viral fitness. See revertant mutation.

bile duct – a tube that carries bile from the liver to the gallbladder and then to the small intestine biopsy: taking a small sample of body tissue for examination and testing in the laboratory

second-line therapy – the combination of used after your first treatment has failed.

CD4 count – number of CD4 cells in a cubic millimetre of blood. CD4 counts results are given as a number that can be anywhere from 0 to over 2000 (rarely).

The range for an HIV-negative person is usually quoted as 430 – 1690. This means 95% of HIV negative people have a CD 4 count between 430 and 1690, but also that a few people have normal levels above or below this. A ‘normal’ CD4 count for an HIV positive person means getting above 500. However, this is an ideal goal and many people remain very well and healthy with CD4 counts that are lower than this.

Test results can also be reported in three main formats. ie a CD4 count of 350 can be written as:

• 350 cells/mm³ (cells per cubic millimetre); or
• 350 cells/μL (cells per microlitre); or
• 350 Χ 10⁶ cells/L (per million cells per litre: i.e.: times 10 to the power of 6, cells per litre)

See: Units of measure.

Since 2015, most treatment guidelines recommend starting treatment at any CD4 count, even when this is above 500.

Once viral load becomes undetectable on HIV treatment (ART), this also stops sexual transmission to HIV negative partners.

somnolence – feeling sleepy or drowsy, especially during the day.