This was published in New Scientist London (26th March 19 87) Excerpt

Probably the most commonly asked question about AIDS is whether the virus spreads through mosquitoes or other blood-sucking insects. Fortunately, the answer is no.

However, because so much has already been written about this subject, it is worth looking at the question in some detail. In theory, there are two ways in which a mosquito or other insect could transmit HIV, the virus that causes AIDS: biologically or mechanically.

Malaria is biologically transmitted when the malaria parasite enters the mosquito, thrives and then makes it’s way~ to the insect’s salivary glands, from which it is injected into another person. This sequence of events is unlikely\ for HIV because the virus appears to replicate in a narrow range of mammalian cells.

The second hypothesis is mechanical transmission, with the virus spreading on the insect’s mouthparts that might become contaminated with blood containing HIV. If a mosquito bit a person infected with the virus and was then disturbed, so that it interrupted it’s feeding, the insect could then fly off to bite another person and perhaps the virus on its mouth parts could be injected into the second person. According to this theory, the insect  then operate like a very’ tiny contaminated needle.

The evidence against mechanical transmission comes from several sources. First, the age and sex distribution of people infected with 1-fly an Africa is typical of a sexually transmitted disease. If insects spread HIV there should be just as much, possibly more infection among young children and old people as among people between 20 and 40 years old. Thus for example, malaria is common among infants and young children in these areas.

Several studies among families of AIDS patients in Africa show that people who live in the same household as AIDS patients were no more likely to be infected with HIV than members of households without an AIDS patients. The exception to this was if they were the sexual partner (spouse) or child of the AIDS patient. Thus in Africa as in the US and Europe, researchers have not found that the virus spreads among people living together, except for sexual partners and transmission between mothers and children. If mosquitoes, bedbugs, lice or other insects living in a crowded African home could spread the virus, we would have expected to find more infected people in the households of AIDS patients.

Another reason why transmission by insect is unlikely is the tiny amount of blood on an insect’s mouthparts. Together with the small quantity of the HIV that seems to be present in the blood of infected persons. These combine to make mechanical transmission even less likely.

The studies of families of people with AIDS also allow us to discount theories about casual spread of AIDS by contact. Also studies of hospital workers showed that HIV was no more contagious from hospital patients to hospital staff in Africa than in the Western world. All the evidence leads us to conclude that the virus is transmitted everywhere in the world in the same basic was’ (sex, blood and mother-to-child), although there are important geographical and social variations.

By Jonathan Mann