David Tilleyshort of Dunedin asks :-

Can HIV be transmitted from an infected person to someone else via a sandfly or mosquito bite?

Leo Celi, a specialist in Infectious Diseases and Intensive Care at Dunedin Hospital, responded.

Yes it is possible but it is highly unlikely.

The virus does not survive well outside the human body. A virus is nothing but genes surrounded by a protein coat. It can only multiply inside the human body, or artificially in monkey cells grown in the laboratory. It cannot be sustained in a sandfly or a mosquito. The virus requires proteins known as receptors to be able to enter a cell where it multiplies. Sandflies and mosquitoes do not have these receptors.

Such transmission is only possible if one is bitten by a sandfly or mosquito immediately after biting someone infected with the virus. Even in this situation, transmission depends on a lot of factors. The most important of these factors is the amount of virus in the bloodstream of the infected person. Unlike other infections such as hepatitis B, persons with HIV do not have a lot of viruses in their bloodstream. A person infected with HIV on effective medications usually does not have detectable virus in his or her bloodstream. He or she is very unlikely to transmit HIV through mosquito or sandfly bites.

The main routes of HIV transmission are through sexual intercourse and mother-to-child transmission at birth. Every single day, up to 15,000 people world-wide become infected with HIV, and every single day, up to 10,000 people die from the infection. In the last three years we have seen the most number of new cases in New Zealand.

HIV is now the worst epidemic known to humans. This year (2007), up to half a million children will die of AIDS. The cost of anti-retroviral treatment for a child is 16 cents a day, or $60 a year. In the meantime, the world spends a trillion dollars a year on things military. We need to mount a concerted effort to solve this crisis.