XI International Conference on AIDS(http://www.interchg.ubc.ca/aids11/homepage.html)
XI International Conference on AIDS(internet-link: "http://www.interchg.ubc.ca/aids11/homepage.html") (Abstract in press)
Keywords: condom, spermicide, n9, HIV, transmission efficacy, heterosexual, window period
Objective: For heterosexuals, 'we have lost the war on condoms'. Including spermicides [1-3] into the message targeted towards heterosexuals is likely to improve compliance. However, as long as a substantial proportion of heterosexuals is failing to comply, because they consider it impractical to practice safer sex indefinitely (or until the partner agrees to be tested) this alone will not necessarily reduce the reproduction number among heterosexuals below the desirable threshold of 0.5. A strategy that requires the use of barrier-methods for a limited period of time only is likely to be more acceptable.
Methods: The spread of HIV among heterosexuals is modeled under the following assumptions: The reproduction number is less than 1.5 among heterosexuals.[4] Heterosexuals engaged in a sexual relationship have the majority of their contacts within the relationship and are less promiscuous than singles. Heterosexuals who never engage in long-term relationships are most likely to import HIV. A person is highly infectious during the 'window-period', where the antibody tests are still negative. Sexual activity reaches its maximum early in a relationship where risk factors in the partner's history are still unknown. The infectivity remains low until the first symptoms appear. At this time, both sexual activity and promiscuity are low because of decreasing sexual attractiveness and disease-related changes in life-style.
Results: Compliance is more important than method effectiveness [2] and it is more important to have a high compliance during the initial period of relationships than to have a passable compliance over the whole duration. This effect is due to an interaction of several factors. (1) Short-term relationships with partners of unknown risk-factors are protected. (2) The 'window period' and the period of 'high sexual activity' are protected. (3) Infections within a long-term relationship are less likely to cause additional infections due to 'saturation' within the relationship.
Conclusions: If most heterosexuals would use condoms or spermicides during the first three months of a relationship (including contacts outside the relationship) the reproduction number would be less than 0.5. Every imported infection would cause (on the average) only one additional infection (including all secondary, tertiary, etc. infections).
Requests for reprints to: Knut M. Wittkowski Department of Medical Biometry, Eberhard-Karls-University, Westbahnhofstr. 55, D-72070 Tübingen, Germany, kmw@uni-tuebingen.de(kmw@uni-tuebingen.de) current address (until 96-09-30): Department of Statistics and Actuarial Science, University of Waterloo, Waterloo, Ontario, Canada, N2L 2G1
[1a] WITTKOWSKI, K.M. (1988) Über die Bedeutung von Detergentien für die HIV-Prophylaxe unter Heterosexuellen. (On the impact of detergents on HIV prevention strategies for heterosexuals.) AIDS-Forschung 3
[2] WITTKOWSKI, K.M. (1989) Preventing the heterosexual spread of AIDS: What is the best advice if compliance is taken into account? AIDS 3 :143-145
[3] WITTKOWSKI, K.M. (1995) The potential of nonoxinol 9 for the prevention of HIV infection reconsidered. AIDS 9
[4a] WITTKOWSKI, K.M. (1995) Epidemiologie von HIV in Deutschland (Epidemiology of HIV in Germany) Das Gesundheitswesen 57
[4b] WITTKOWSKI, K.M. (1995) Die Ausbreitung von HIV unter Heterosexuellen in Deutschland anhand der Zahlen des AIDS-Fallregisters, Stand 31.07.95. Das Gesundheitswesen 57 : 528 (abstract)
[4c] WITTKOWSKI, K.M. (1996) Epidemiologie von HIV in Deutschland (Stand 30.06.95) - Ausbreitung unter Heterosexuellen und Aussagekraft von HIV-Screening-Programmen Das Gesundheitswesen 58 : 229-233
Related presentations at the XI International Conference on AIDS(internet-link: "http://www.interchg.ubc.ca/aids11/homepage.html") :
Other publications on HIV and AIDS , HIV Epidemiology in Germany
Back to: Knut M. Wittkowski's homepage
On to: Publications and presentations of Knut M. Wittkowski
XI International Conference on AIDS(http://www.interchg.ubc.ca/aids11/homepage.html)
XI International Conference on AIDS(http://www.interchg.ubc.ca/aids11/homepage.html)