A QUANTUM OF SCIENCE
Are HIV rates in the US substantial enough to merit a policy of circumcision?
Following evidence of the protective effect against HIV infection, recent news articles report that the CDC is mulling the idea of endorsing circumcision for all male infants born in the United States. But will it have that much impact?
First, the science: how does circumcision prevent HIV infection? HIV infections occur when the virus gains entry to cells by binding to a protein called CD4, found on the surface of cells. Cell types rich in CD4 are thus easier targets for a successful HIV infection. One such cell type is the Langerhans cell, a part of the primate epidermal tissue related to defending the body against invading microbes. As it happens, primate foreskin is rich in Langerhans cells, meaning plenty of CD4 protein for the AIDS virus to bind to and invade the body. By removing the foreskin through circumcision, an easy point of entry for the virus is blocked.
(Interestingly, CD4-rich Langerhans cells are found in human foreskin and vaginal tissues, but not in oral or rectal tissues. This suggests that HIV infections use a different biochemical route when introduced into the body through those tissues.)
The idea of reducing the risk of contracting HIV through circumcision is far from new. In 1987 a letter was published in the New England Journal of Medicine suggesting exactly that, and studies done in the last fifteen years bear out that theory. While the methods used and areas studied (largely in Africa) varied, the conclusions were so striking that in at least one case a circumcision/HIV infection study was halted years early so the findings could be considered for public policy discussions. Depending on the area studied and the risk factors of those involved in the study, HIV infection rates were found to be as much as 50% lower among circumcised African men than their intact counterparts. Various attempts have been made to expand the conclusions of individual studies through meta-analysis papers and their conclusions found an even greater protective effect of circumcision when those studied were from high-risk populations.
So why not support a policy of encouraging circumcision in the United States? The same studies being reviewed by the CDC have some counterindications that are well worth considering in any kind of policy discussion.
First, the benefits of circumcision are greatly enhanced among high-risk populations. This means that for the average American man (whose risk is far, far lower than the average African man) the benefits are considerably lessened. This could well have something to do with the fact that an estimated 79% of American men are already circumcised – though as rates of circumcision have fallen to around 65% in the most recent surveys, that number is now trending downward. Secondly, use of barrier protection is far more prevalent in America among all demographics, another factor that reduces the positive impact of circumcision protection. Another risk factor related to the need for additional preventative measures against HIV infection – the rate of STDs causing lesions or ulcers, such as herpes or syphilis, which help HIV enter the body during sexual contact – is lower in America than in most African nations, and treatment for those afflictions is considerably more available. Finally, almost all the research done in this area has been performed in Africa. This means there is a possibility that things could be different among Caucasian populations, simply because they are biochemically distinct from non-Caucasians.
The need for additional research is clear. Until scientists can repeat the highly successful African studies in America, Europe, or ideally both – since circumcision is much less common in European nations than in America – the benefits of circumcision for Western populations will remain a question too open for a substantive policy debate to take place.
For more information:
CDC mulls routine circumcision of infants to reduce spread of HIV (NY Daily News, 25-Aug-09)
Circumcision and heterosexual transmission of HIV infection to men. (Fink, 1987)
Comparative investigation of Langerhans' cells and potential receptors for HIV in oral, genitourinary and rectal epithelia. (Hussain, 1995)
Male circumcision and risk of HIV infection in sub-Saharan Africa: a systematic review and meta-analysis. (Weiss, 2000)
Male circumcision for HIV prevention in young men in Kisumu, Kenya. (Bailey, 2007)
Langerhans cells.
© AQOS / P. Smalley (2009)
Reproduction with attribution is appreciation
Showing posts with label policy. Show all posts
Showing posts with label policy. Show all posts
Tuesday, August 25, 2009
Wednesday, July 8, 2009
Food Safety Overhaul: Chickens and Eggs
A QUANTUM OF SCIENCE
Sweeping and ambitious, administration regulations would enact mandatory oversight and tracking of critical foods
Today the Obama administration announced a major overhaul of the US food safety system. Overseen almost entirely by the FDA, some 150,000 individual commercial food producers would be subject to sweeping new regulations that would require traceability for all food and food additives sold in the US. This is a significant increase in the level of government oversight of the food industry and is a response to several high-profile outbreaks of food poisoning in the last several years. These include recent E. coli and Salmonella outbreaks leading to the recall of tremendous amounts of food throughout the US. Notably, Salmonella in peanut products and E. coli in ground beef both originated in US commercial food manufacturers as a result of poor hygiene and lack of mandatory safety regulations. Worse still, it took unconscionably long for the FDA to track down exactly where the problem started, leading to a much larger outbreak than necessary.
To prevent this from happening again, the new legislation calls for a Reportable Food Registry to be established and overseen by the FDA. This registry would ensure that any outbreak of food poisoning or adulterated food would be instantly reported to the FDA, which would then be able to use the registry to track down where the adulterated food came from, what other foods it might have come in contact with or been used in, and what distributors to alert. Not only would this increase the response time of the FDA, it would also allow traceability for the agency such that random testing of large numbers of those 150,000 individual commercial food manufacturers would not be required. If a tomato in Denver turned up positive for Salmonella, FDA scientists could quickly determine that it came from a wholesaler in Texas who purchased it from a grower in Louisiana. From there, all tomatoes that came from that grower or that passed through that wholesaler would be identified and the distributors notified to pull the tomatoes off their shelves.
This is a massive undertaking but a significant benefit to the food safety network in the US. Previously it might have taken FDA scientists weeks to trace a single infected tomato back to that grower in Louisiana, and in that time panicked distributors might destroy untold volumes of perfectly safe tomatoes, costing the food industry huge amounts of money. With the Registry, that process might take less than 48 hours, and the cost savings to distributors and wholesalers is the reason that the food industry generally supports this legislation.
One particular area of concern for the Obama administration is eggs – specifically, chickens, eggs, and Salmonella. It has been known for twenty years that infected chicks produce Salmonella-laden eggs that cannot be detected easily by the current food safety inspection systems in place. The new legislation mandates that egg growers take steps to eliminate rodents (a prime source of Salmonella contamination) and only purchase chicks from growers who also take steps to monitor Salmonella among their stock. Additional regulations require refrigeration during more of the lifespan of an egg, something that about half of all egg producers already do voluntarily and which would reduce the potential for Salmonella growth. As mentioned above, egg growers are generally in favor of these regulations – even though it will cost them some money for testing and prevention, they believe the increase in public confidence will more than make up for the estimated one-cent per dozen increase in the cost of eggs.
They’re almost certainly right. In this case, it doesn’t matter whether the chicken or the egg came first, so long as both of them come before the Salmonella.
For more information:
FDA Reportable Food Registry
Article from The Washington Post on the new legislation
New York Times article focusing on egg safety regulations
© A Quantum of Science / P. Smalley
Reproduction with attribution is appreciation
Sweeping and ambitious, administration regulations would enact mandatory oversight and tracking of critical foods
Today the Obama administration announced a major overhaul of the US food safety system. Overseen almost entirely by the FDA, some 150,000 individual commercial food producers would be subject to sweeping new regulations that would require traceability for all food and food additives sold in the US. This is a significant increase in the level of government oversight of the food industry and is a response to several high-profile outbreaks of food poisoning in the last several years. These include recent E. coli and Salmonella outbreaks leading to the recall of tremendous amounts of food throughout the US. Notably, Salmonella in peanut products and E. coli in ground beef both originated in US commercial food manufacturers as a result of poor hygiene and lack of mandatory safety regulations. Worse still, it took unconscionably long for the FDA to track down exactly where the problem started, leading to a much larger outbreak than necessary.
To prevent this from happening again, the new legislation calls for a Reportable Food Registry to be established and overseen by the FDA. This registry would ensure that any outbreak of food poisoning or adulterated food would be instantly reported to the FDA, which would then be able to use the registry to track down where the adulterated food came from, what other foods it might have come in contact with or been used in, and what distributors to alert. Not only would this increase the response time of the FDA, it would also allow traceability for the agency such that random testing of large numbers of those 150,000 individual commercial food manufacturers would not be required. If a tomato in Denver turned up positive for Salmonella, FDA scientists could quickly determine that it came from a wholesaler in Texas who purchased it from a grower in Louisiana. From there, all tomatoes that came from that grower or that passed through that wholesaler would be identified and the distributors notified to pull the tomatoes off their shelves.
This is a massive undertaking but a significant benefit to the food safety network in the US. Previously it might have taken FDA scientists weeks to trace a single infected tomato back to that grower in Louisiana, and in that time panicked distributors might destroy untold volumes of perfectly safe tomatoes, costing the food industry huge amounts of money. With the Registry, that process might take less than 48 hours, and the cost savings to distributors and wholesalers is the reason that the food industry generally supports this legislation.
One particular area of concern for the Obama administration is eggs – specifically, chickens, eggs, and Salmonella. It has been known for twenty years that infected chicks produce Salmonella-laden eggs that cannot be detected easily by the current food safety inspection systems in place. The new legislation mandates that egg growers take steps to eliminate rodents (a prime source of Salmonella contamination) and only purchase chicks from growers who also take steps to monitor Salmonella among their stock. Additional regulations require refrigeration during more of the lifespan of an egg, something that about half of all egg producers already do voluntarily and which would reduce the potential for Salmonella growth. As mentioned above, egg growers are generally in favor of these regulations – even though it will cost them some money for testing and prevention, they believe the increase in public confidence will more than make up for the estimated one-cent per dozen increase in the cost of eggs.
They’re almost certainly right. In this case, it doesn’t matter whether the chicken or the egg came first, so long as both of them come before the Salmonella.
For more information:
FDA Reportable Food Registry
Article from The Washington Post on the new legislation
New York Times article focusing on egg safety regulations
© A Quantum of Science / P. Smalley
Reproduction with attribution is appreciation
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