Semen

Published: 07 April 2009

Between 10 and 30% of seminal fluid samples of HIV-positive men have been shown to contain either free infectious virus or cell-associated virus (infected lymphocytes). However, levels of cell-associated virus are much higher; there are up to one million lymphocytes in each millilitre of semen; even if only one per cent of these lymphocytes are infected with HIV, this means that each millilitre of semen may contain up to 1000 infected lymphocytes. The average male ejaculation is 5ml of semen, although this varies considerably.

Lymphocytes and cell-associated virus are most likely to be present in individuals suffering from infections which cause inflammation in the urethra and other regions of the genital tract. Untreated sexually transmitted infections, even those which cause no detectable symptoms, are likely to increase the viral load in semen.

Several studies have shown a trend towards higher levels of HIV in semen when plasma viral load is also high, and HIV can be isolated much more easily from the semen of individuals who have CD4 counts below 200 cells/mm3.

HIV-infected cells have been detected in pre-ejaculatory fluid (pre-cum) in a siginificant proportion of HIV-positive men. It is unclear whether the quantities isolated are sufficient to lead to infection. 1 2

The relationship between viral load in blood and viral load in semen is discussed in more depth in a later section.

References

  1. Ilaria G et al. Detection of HIV-1 DNA sequences in pre-ejaculatory fluid. Lancet 340: 1469, 1992
  2. Pudney J et al. Pre-ejaculatory fluid as potential vector for sexual transmission of HIV-1. Lancet 340: 1470, 1992
This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.
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This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.

NAM’s information is intended to support, rather than replace, consultation with a healthcare professional. Talk to your doctor or another member of your healthcare team for advice tailored to your situation.