posted 03-15-2001 02:46 AM         

http://www.ucsf.edu/daybreak/1997/08/826_aids.htm
UCSF article on rate of Heterosexual HIV transmission

http://www.cdpc.com/s6.htm
HIV transmission through unprotected sexual intercourse has a markedly
lower efficiency rate compared with blood transfusion or perinatal
exposure.The risk of acquiring HIV through sexual intercourse depends
on the probability that sex partners are infected, the type and number
of sexual contacts with those partners, and whether condoms are
properly and consistently used. The probability that a partner is HIV-
infected is higher in some areas than in others, but the risk of
exposure to HIV through sexual contact exists throughout the world.
According to published studies, HIV transmission rates per single
sexual contact with an HIV-infected partner range from 1/100 to 1/1000.
However, the cumulative risk for someone who has exposures to multiple
sex partners increases with each exposure. Several co-factors that
increase either individual susceptibility or individual infectivity may
play a role in HIV transmission. These include genital ulcers, other
sexually transmitted diseases, and possibly lack of circumcision in
men. The risk of HIV transmission from oral-genital sex is not known,
but is considered to be low.

http://publish.uwo.ca/~ahpandya/HIV12.html
ii) Female-to-male Transmission
Female-to-male sexual transmission of HIV, like transmission of other
STDs, appears less efficient than male-to-female transmission.
Transmission from infected women to their male partners has been poorly
studied. Even in regions where HIV is predominantly acquired through
heterosexual contact, few data are available. It is impossible to
confidently put a number on the risk of such transmissions. A partner
study done by Padian et al. reported only one case of seroconversion
among male partners of 72 monogamous heterosexual couples in which the
female was HIV positive. However, in a similar study done by the
European Study Group on Heterosexual Transmission of HIV, 19 of 159
(12%) of male partners became infected. Higher rates of female-to-male
transmission in this study compared to the findings of Padian et al.
may reflect a different distribution of cofactors that promote
transmission, unacknowledged risks among male partners, and random
variation in both studies. Larger studies are needed in order to make
more conclusive deductions. 9,12,14

i) Male-to-female transmission
The predominant mode of documented heterosexual transmission has been
male-to-female transmission. Retrospective studies of partners of HIV-
infected haemophiliacs and their female sex partners have been
particularly valuable because investigators have been able to enrol
relatively large numbers of sexually active couples in which the female
partners generally had no other risk factors and were much likelier to
have a monogamous relationship.5 Published results of these studies
suggest that approximately 10% of the regular female sex partners of
infected haemophiliac men have themselves become infected with HIV.8
Other studies have determined this risk to be as high as 15% or even
30% among other heterosexual groups (non-haemophiliacs).2,9,10 The risk
of infection through a single exposure is extremely low. In a study
done by Padian et al. this risk was estimated at less than 0.002 per
sexual encounter. However, this risk is very difficult to calculate
since although some remain uninfected after hundreds of unprotected
sexual contacts, others have become infected after only a few
encounters.11,12 It seems that this risk is different for different
populations or geographic locations. For example, as mentioned before,
in Africa where the HIV epidemic has the highest proportions, most of
the viral spread has occurred through heterosexual transmission,
indicating a seemingly more efficient transmission than in North
America. A community based cohort study done by Dr. Francis Plummer on
prostitutes from one area in Nairobi demonstrated that 67% of 124
uninfected prostitutes seroconverted to HIV-1 over a 30 month follow-
up.13 This dichotomy between the heterosexual transmission of HIV in
Africa and the West is a major unanswered question in the epidemiology
of HIV-1 transmissibility. These findings all imply that other factors
come into play affecting the transmissibility of HIV.

http://www.sfaf.org/treatment/beta/b41/b41sexual.html
Several researchers have attempted to quantify the HIV transmission
risk associated with specific sexual activities, with widely varying
results. At the 5th CROI in February 1998, E. Vittinghoff presented
estimates of the per-contact risk of various male-to-male sexual
activities. He found a 0.0024 probability of transmission per contact
for unprotected receptive anal sex, and a 0.0003 probability for both
unprotected insertive anal intercourse and unprotected receptive oral
sex. Mitchell Katz, MD, of the San Francisco Department of Public
Health, and Julie Gerberding, MD, now with the CDC, reviewed the
medical literature on the probability of HIV transmission via several
specific routes in the April 10, 1997 issue of the New England Journal
of Medicine (see table, below).

Probability of Transmission Associated with Specific Types of Exposure
to HIV *
Unprotected receptive anal intercourse: 0.008 to 0.032(80 in 10,000 to
320 in 10,000)
Use of HIV-contaminated drug injection equipment: 0.0067 (67 in
10,000)
Contaminated needlestick exposure by health-care worker: 0.0032
(32 in 10,000)
Unprotected receptive vaginal intercourse: 0.0005 to 0.0015(5 in
10,000 to 15 in 10,000)
Unprotected insertive vaginal intercourse: 0.0003 to 0.0009(3 in
10,000 to 9 in 10,000)
Unprotected insertive anal intercourse: no data, but believed to be
similar to unprotected insertive vaginal intercourse
Unprotected oral sex: no per-exposure estimates, but cases have been
documented in the medical literature
*Rates are for a single exposure of the type indicated; ranges indicate
the rates found in different studies.
Adapted from Katz, M.H. and Gerberding, J.L. Postexposure treatment of
people exposed to the human immunodeficiency virus through sexual
contact or injection drug use. New England Journal of Medicine 336(15):
1097-1099. April 10, 1997.

http://hivinsite.ucsf.edu/akb/1997/01sextx/table1a.html
Table 1. HIV Infectivity per Sexual Act

Sexual Behavior Range of Infectivity Estimates Reference

Receptive anal intercourse 0.008 - 0.032 78
Vaginal intercourse (risk to woman) 0.0003 - 0.002 79,80
Vaginal intercourse (risk to man) 0.0003 - 0.0014* 80

* A much higher estimate of 0.056 was made by a study of Thai army
recruits,but as this is an extreme outlier, it is not included in the
table.( reference 81)

© 1998 "The AIDS Knowledge Base" editors. All rights reserved.
May not be reproduced electronically or in other forms, or otherwise
reproduced for any purpose without written permission.

http://hivinsite.ucsf.edu/prevention/ask/2098.3c1e.html
You are correct. According to results from the Northern California
Partner's Study, published last year, (Padian, NS, Shiboski, SC, Glass,
SO, Vittinghoff, E. Heterosexual transmission of human immunodeficiency
virus (HIV) in northern California: Results from a ten-year study.
American Journal of Epidemiology. 1997; 146(4): 350-57.)
Male-to-female transmission was approximately eight-times more
efficient than female-to-male transmission and male-to-female per
contact infectivity was estimated to be 0.0009 (95% C 0.0005-0.001).

http://hivinsite.ucsf.edu/akb/1997/01sextx/index.html#Dc
Estimates of HIV-1 Infectivity
By using data from studies of heterosexual couples and from individuals
seroconverting in longitudinal studies, a number of estimates of HIV
infectivity have been derived by researchers using mathematical models.
Because HIV infection is a binomial outcome (it occurs or it does not
occur with each sexual contact), the cumulative probability of being
infected (P) after n sexual contacts can be expressed with the formula:
P = 1 - (1 - k)n
in which k is the infectivity parameter, the probability that a single
sexual contact transmits HIV. In this simple model, it is assumed that
all sexual contacts across all sexual partners carry a constant risk.
The model can be modified to reflect the probability that a given
sexual partner is infected and to allow for an infectivity that is not
constant. By taking a log-log transformation of the preceding equation,
an expression is obtained with two linear terms that can be analyzed in
a general linear model that permits accounting for covariates such as
condom use, stage of HIV disease of partners, and other variables that
affect transmission probability.(77) Using such techniques and related
mathematical models, a range of estimates of the infectivity of HIV
have been derived (Table 1). Estimates have not been published for
other sexual behaviors. The data summarized earlier in this chapter
from studies of incident infections in homosexual men suggest that the
infectivity of insertive anal intercourse is at least a log lower than
receptive anal intercourse, and receptive oral intercourse infectivity
is lower still.

http://www.cdc.gov/hiv/stats/exposure.htm
Basic Statistics - Exposure Categories
The following data are from the CDC semiannual HIV/AIDS Surveillance
Report. Numbers are based on AIDS cases reported to CDC through June
2000.

Following is the distribution of reported AIDS cases among adults and
adolescents by exposure category. A breakdown by sex is provided where
appropriate. The categories and totals are:
AIDS CASES BY EXPOSURE CATEGORY
EXPOSURE CATEGORY MALE FEMALE TOTAL*
Men who have sex with men 348,657 - 348,657
Injecting Drug Use 137,650 51,592 189,242
Men who have sex with men and inject drugs 47,820 - 47,820
Hemophilia/coagulation disorder 4,847 274 5,121
Heterosexual contact 27,952 50,257 78,210
Recipient of blood transfusion, blood components, or tissue 4,920
3,746 8,666
Risk not reported or identified 48,343 19,042 67,387
* Includes 3 persons whose sex is inknown.

http://www.cdc.gov/hiv/stats/topten.htm
Basic Statistics - Ten States/Territories and Cities Reporting Highest
Number of AIDS Cases The following data are from the CDC semiannual
HIV/AIDS Surveillance Report. Numbers are based on AIDS cases reported
to CDC through June 2000. The 10 leading states or territories
reporting the highest number of cumulative AIDS cases among residents
as of June 2000 are as follows:TEN STATES/TERRITORIES REPORTING HIGHEST
NUMBER OF CUMULATIVE AIDS CASES
STATE/TERRITORY # of CUMULATIVE AIDS CASES
New York 139,248
California 117,521
Florida 78,043
Texas 52,667
New Jersey 41,245
Illinois 24,425
Puerto Rico 24,061
Pennsylvania 23,678
Georgia 22,197
Maryland 20,833
The 10 leading metropolitan statistical areas reporting the highest
number of cumulative AIDS cases among residents as of June 2000 are as
follows:TEN METROPOLITAN AREAS REPORTING HIGHEST NUMBER OF CUMULATIVE
AIDS CASES
METROPOLITAN AREA # of CUMULATIVE AIDS CASES
New York City 117,792
Los Angeles 41,394
San Francisco 27,567
Miami 23,521
Washington, DC 22,321
Chicago 21,173
Houston 18,735
Philadelphia 18,348
Newark 16,739
Atlanta 15,524

Last Updated: January 2, 2001
Centers for Disease Control & Prevention
National Center for HIV, STD, and TB Prevention
Divisions of HIV/AIDS Prevention
Please send comments/suggestions/requests to: hivmail@cdc.gov

http://hivinsite.ucsf.edu/akb/1997/01sextx/
AIDS Knowledge Base

Why has the British Govt, added economic refugees and former Sub-Saharan Nationals to the HIV/AIDS figures? Over 1,300 "heterosexual cases" have been added.
Why? Because in 20 years there have been a total of 207 heterosexual cases of HIV in the UK, amongst white non-drug users.
That is just over 10 a year in 20 years.
Call this an epidemic?

Go here;
http://www.********************/ppbrodybook.html

And here;

http:/www.virusmyth.net/aids/data/rrbprostitute.html

This Virus seems a lot more difficult to catch than I first thought

Stan56