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HIV-AIDS prevalence estimates: art or science?
Newsdesk Bloodsucking fly blamed for transmitting HIV tract”. They pointed to earlier studies showing that S calcitrans can transmit equine anaemia virus in horses. The new theory presents the possibility that the current HIV
Werner Kloft
The bloodsucking stable fly Stomoxys calcitrans could have been responsible for beginning the HIV pandemic, according to a new theory put forward in Naturwissenschaften by Gerhard Brandner (University of Freiburg, Germany), Werner Kloft (University of Bonn, Germany), and Manfred Eigen (Max Planck Institute for Biophysical Chemistry, Göttingen, Germany). Most bloodsucking insects are not capable of transmitting HIV because they inject saliva and ingest blood through different routes. However, S calcitrans might be an exception. Brandner and Kloft showed previously that HIV can survive in blood regurgitated by this insect because “the anterior part of the mid-gut where the regurgitate is kept is just for storage, and is free of digestive enzymes”. With regard to isolating HIV from S calcitrans, Brandner and Kloft said: “we have been able to do this from the flies’ regurgitates but we have not tried to dissect the flies to obtain HIV material from the lower digestive
A taste for HIV
pandemic was started when S calcitrans transmitted the virus from chimpanzees to people. According to Brandner et al, “apes are traditionally hunted in Africa and are offered for sale in open-air meat markets. The bloody carcasses are regularly covered with blood-feeding flies, possibly including the stable fly”. The flies could have ingested HIV-infected blood from chimpanzees and
transmitted the virus when they subsequently fed on humans. Brandner et al emphasise “that any speculations on a possible role of the hypothetical vector for the present rapid expansion of AIDS in Africa, and elsewhere, are inappropriate”. A note of caution was expressed by Beatrice Hahn (University of Alabama, USA), who was the first to find evidence for west central African chimpanzees harbouring the closest SIV relatives of HIV-1. She feels that it is a big leap to go from finding HIV in regurgitated blood in S calcitrans in an experimental system to the bushmeat scenario. She would also like to know more about the prevalence of this insect in west central Africa. If the theory was correct, and HIV was transmitted from chimpanzee bushmeat to human beings by S calcitrans, Hahn questions why this fly is not spreading HIV-1 today by this very same route. To the best of her knowledge, there is no epidemiological evidence for this. Cathel Kerr
HIV-AIDS prevalence estimates: art or science? UNAIDS is finalising its latest global HIV-AIDS estimates ready for publication just before the XIV World AIDS Conference (Barcelona, Spain, July 7–12, 2002). According to Neff Walker of UNAIDS, agreement has been reached with most countries about these estimates, including with those who have in the past disagreed with UNAIDS estimates (see TLID, April 2002, p 199). Estimates of HIV-AIDS indicate the progress of the epidemic and permit rational decisions to be made about resource allocation. However, for most countries, estimates are not based on reported HIV infections or AIDS cases because the data are generally very incomplete. “In developing countries, we use sentinel surveillance data”, explains Walker. “In Africa, for example, pregnant women have their blood drawn for syphilis testing. These samples are also tested for HIV, and we can translate
these data into a prevalence for the whole population.” Walker adds that, “in countries with good surveillance systems, our estimate is plus or minus 20% of the true prevalence”. This degree of accuracy, he adds, “is more than adequate to give a good snapshot of what is happening in the epidemic”. In many western European countries, HIV surveillance is largely based on AIDS reporting, and HIV prevalence estimates have historically been done by back-calculation. However, with the advent of highly active antiretroviral treatment, these data are becoming increasingly hard to interpret, says Francoise Hamers of the EuroHIV surveillance network. Reporting of newly diagnosed HIV infection would provide more timely data unaffected by treatment, she says, but although implemented in most European countries, such surveillance still only covers half of the population
THE LANCET Infectious Diseases Vol 2 May 2002
http://infection.thelancet.com
of western Europe and not the most affected countries. In France, for example, says Hamers, “the Ministry of Health has been trying to set up a national HIV reporting system for 3 years but people are afraid of breach of confidentiality”. For a handful of countries, estimates of HIV-AIDS prevalence are based on reported cases of HIV infection. In these countries, estimates can be made of the proportion of infected individuals who are undiagnosed. Using this method, Patricia Fleming of the US Centers for Disease Control and Prevention (Atlanta, GA, USA) reported in February 2002 that about 25% of infected individuals in the USA were unaware of their status. But even in the USA not all states report HIV infections, so even here, says Walker, “it may still be hard to estimate nationwide prevalence from case reporting”. Jane Bradbury
265
For personal use. Only reproduce with permission from The Lancet Publishing Group.
Werner Kloft
The bloodsucking stable fly Stomoxys calcitrans could have been responsible for beginning the HIV pandemic, according to a new theory put forward in Naturwissenschaften by Gerhard Brandner (University of Freiburg, Germany), Werner Kloft (University of Bonn, Germany), and Manfred Eigen (Max Planck Institute for Biophysical Chemistry, Göttingen, Germany). Most bloodsucking insects are not capable of transmitting HIV because they inject saliva and ingest blood through different routes. However, S calcitrans might be an exception. Brandner and Kloft showed previously that HIV can survive in blood regurgitated by this insect because “the anterior part of the mid-gut where the regurgitate is kept is just for storage, and is free of digestive enzymes”. With regard to isolating HIV from S calcitrans, Brandner and Kloft said: “we have been able to do this from the flies’ regurgitates but we have not tried to dissect the flies to obtain HIV material from the lower digestive
A taste for HIV
pandemic was started when S calcitrans transmitted the virus from chimpanzees to people. According to Brandner et al, “apes are traditionally hunted in Africa and are offered for sale in open-air meat markets. The bloody carcasses are regularly covered with blood-feeding flies, possibly including the stable fly”. The flies could have ingested HIV-infected blood from chimpanzees and
transmitted the virus when they subsequently fed on humans. Brandner et al emphasise “that any speculations on a possible role of the hypothetical vector for the present rapid expansion of AIDS in Africa, and elsewhere, are inappropriate”. A note of caution was expressed by Beatrice Hahn (University of Alabama, USA), who was the first to find evidence for west central African chimpanzees harbouring the closest SIV relatives of HIV-1. She feels that it is a big leap to go from finding HIV in regurgitated blood in S calcitrans in an experimental system to the bushmeat scenario. She would also like to know more about the prevalence of this insect in west central Africa. If the theory was correct, and HIV was transmitted from chimpanzee bushmeat to human beings by S calcitrans, Hahn questions why this fly is not spreading HIV-1 today by this very same route. To the best of her knowledge, there is no epidemiological evidence for this. Cathel Kerr
HIV-AIDS prevalence estimates: art or science? UNAIDS is finalising its latest global HIV-AIDS estimates ready for publication just before the XIV World AIDS Conference (Barcelona, Spain, July 7–12, 2002). According to Neff Walker of UNAIDS, agreement has been reached with most countries about these estimates, including with those who have in the past disagreed with UNAIDS estimates (see TLID, April 2002, p 199). Estimates of HIV-AIDS indicate the progress of the epidemic and permit rational decisions to be made about resource allocation. However, for most countries, estimates are not based on reported HIV infections or AIDS cases because the data are generally very incomplete. “In developing countries, we use sentinel surveillance data”, explains Walker. “In Africa, for example, pregnant women have their blood drawn for syphilis testing. These samples are also tested for HIV, and we can translate
these data into a prevalence for the whole population.” Walker adds that, “in countries with good surveillance systems, our estimate is plus or minus 20% of the true prevalence”. This degree of accuracy, he adds, “is more than adequate to give a good snapshot of what is happening in the epidemic”. In many western European countries, HIV surveillance is largely based on AIDS reporting, and HIV prevalence estimates have historically been done by back-calculation. However, with the advent of highly active antiretroviral treatment, these data are becoming increasingly hard to interpret, says Francoise Hamers of the EuroHIV surveillance network. Reporting of newly diagnosed HIV infection would provide more timely data unaffected by treatment, she says, but although implemented in most European countries, such surveillance still only covers half of the population
THE LANCET Infectious Diseases Vol 2 May 2002
http://infection.thelancet.com
of western Europe and not the most affected countries. In France, for example, says Hamers, “the Ministry of Health has been trying to set up a national HIV reporting system for 3 years but people are afraid of breach of confidentiality”. For a handful of countries, estimates of HIV-AIDS prevalence are based on reported cases of HIV infection. In these countries, estimates can be made of the proportion of infected individuals who are undiagnosed. Using this method, Patricia Fleming of the US Centers for Disease Control and Prevention (Atlanta, GA, USA) reported in February 2002 that about 25% of infected individuals in the USA were unaware of their status. But even in the USA not all states report HIV infections, so even here, says Walker, “it may still be hard to estimate nationwide prevalence from case reporting”. Jane Bradbury
265
For personal use. Only reproduce with permission from The Lancet Publishing Group.