AIDS Conference 1992 – session 3 Dr. John Kaldor

Speech given by Dr. John Kaldor

Associate Professor in Epidemiology and Deputy Director of the National Centre for HIV Epidemiology and Clinical Research

Conference Paper: AIDS – Have we got it Right?

A conference organised by The Australian Doctors Fund Ltd.

Hosted by Professor Fred Hollows & ADF Chairman Dr. Bruce Shepherd

Sheraton Sydney Airport Hilton

May 14th and 15th, 1992

Transmission of HIV in Australia

• The table below shows that the vast majority of cases of HIV as reflected by AIDS cases in Australia have been acquired through sex between men.
• The second most frequent mode of transmission has been through medical procedures.
• Other modes of transmission have been responsible for a much smaller number of cases.

Sexual transmission of HIV between men

• A peak in transmission was reached in 1983-84 and there was a rapid decline thereafter.
• Conclusions regarding a peak are based on back projection from AIIDS cases. This method has some limitations, but under all plausible assumptions, produces consistent results with regard to this overall pattern.
• Transmission still occurs through sex between men, although certainly at rates much lower than those in the mid-1980s.
• It is difficult to determine recent trends in transmission rates or to know whether any particular sub-group of men having homosexual contact is at higher risk.
• Other information corroborating a decline in sexual transmission between men comes from studies in clinical and cohort studies, trends in other STD’s such as gonorrhoea and studies of trends in sexual behaviour.
• Possible explanations for the decline in transmission observed in the mid-1980s are behavioural changes resulting from the rapid spread of information about HIV. It is theoretically possible that behavioural change may have only occurred in the subgroup who are at a particularly high risk of infection.

Injecting drug users

• Based on available prevalence surveys, there is a very low rate of HIV infection in injecting drug users in Australia, apart from men who had homosexual contact. Back projection from AIDS cases and longitudinal clinical studies provides only limited information, because numbers of cases are small.Corroboration of the prevalence studies comes from the results of HIV testing of prisoners (prevalence .1%), absence of HIV in blood donors found to have hepatitis C and declining rates of hepatitis B.
• Current trends are not clear and information collection is at present limited. Available information from surveys shows that injecting drug users continue to share injecting equipment. It is possible that low rates of HIV in this group have been a consequence of fortuitous patterns of sharing.

Heterosexual transmission of HIV

• No study population can be said to be truly representative of people having heterosexual contact. The main sources of information on heterosexual transmission have been blood donors, STD clinics and pregnant women/newborns.
• HIV prevalence in blood donors has remained very low since screening began (1 per 100,000).
• Information from STD clinics also indicates a low rate of heterosexual HIV transmission, but demonstrates that an increasing proportion of other STD’s are being acquired through heterosexual contact with Southeast Asian prostitutes, whether in Australia or in Southeast Asia.
• Available data on pregnant women also support a low rate of heterosexually-transmitted HIV infection.
• Current patterns are not clear and no current monitoring system would allow the ready detection in increases in prevalence from, say, 1 in 100,000 to 1 in 20,000.
• The extent of the heterosexual HIV transmission is closely linked to patterns of transmission in other groups, particularly injecting drug users.
• Available studies suggest that knowledge and awareness is high, but there has been limited change in sexual practice.

Other questions

• There have been no known cases of HIV transmission through blood products since 1985.
• There has been no known HIV transmission within prisons.
• There have been two cases of occupational HIV transmission through needle stick injury in Australia.
• In some Aboriginal communities the conditions which have been predicted to give rise to a major heterosexual epidemic of HIV still remain, but there is no indication that such an epidemic has begun.