Question of The Week:
“I have an incredibly stupid question … If HSV is not included on the STD panel, then how do we know that 70-80% of the population has it??? If folks aren’t tested then how do we know?”
Not a stupid question at all. There are no stupid questions. A lot of people wonder this and many somehow conclude that they couldn’t possibly know, thinking that the only people they’d be counting are those who show up at a doctor. How can you test someone who doesn’t come in, right? Well, that isn’t at all how they come up with their numbers.
The NHANES – the National Health and Nutrition Examination Survey is an offshoot of the US Census. The US Census does a lot more than just Q&A stuff. They recruit people for the NHANES, too… where the CDC pokes, prods and tests them for a big list of things. HSV-1 and HSV-2 are two of those things. Once complete, the National Center for Healthcare Statistics(NCHS) compiles the data.
In the NHANES they develop sample groups, carefully selected to for a model of the US population as a whole. During their interview and examination stage, they ask 100% of them (within the age group they’re studying; often 14-49 yrs) ahead of time if they’ve ever been told by a medical professional that they have Genital Herpes. After testing, it turned out that 81.1% of those who tested positive for HSV-2 answered “No”, while 18.9% of those who tested positive had answered “yes”. From that, it is determined that these are the numbers among the population which are diagnosed(18.9%) and undiagnosed(81.1%); asymptomatic enough, at least, to not feel the need to see their doctor. Obviously, in all of this, they also end up knowing the total percentage who test positive for HSV-2 regardless of whether or not they were ever aware of it.
Similar numbers are derived regularly in a rather similar fashion in other research studies. While they may vary slightly, they generally come up with between 80% and 90% of the positives having been undiagnosed/asymptomatic and 10-20% having been diagnosed or symptomatic. The consistency of the results only serves to strengthen the case that this is indeed the state of the HSV-2 situation across the US.
They do the same thing for HSV-1, too. Combined, around 75% test positive for HSV-1, HSV-2 or both. 80%-90% of those who do so did not appear to be aware that they were.
While that answers the asymptomatic/symptomatic question pretty well, these studies also answer the questions “How many people carry HSV-1?”, “How many people carry HSV-1?” and “How many people carry both?” What they do not answer, however, is “Exactly where ARE all of these infections? The NHANES can’t answer that by giving blood tests for antibodies, so some assumptions have been made in the past:
- That all HSV-2 infections were genital
- That all genital herpes infections were HSV-2
Both of these are known to not be quite true. The former is likely “mostly true”, while the latter isn’t true by a long shot.
The CDC-reported Genital Herpes statistics – 16.2% and “1 in 6” – really only include those who test positive in a blood antibody test for HSV-2. That would not include HSV-1 infections,. They barely even mention HSV-1 and cold sores at the CDC. Around 2/3 of the country carries HSV-1, which is equally capable of giving a partner genital herpes; mainly through oral sex, as that’s where people most often carry it, although either HSV type is capable, to varying degrees, of infecting any surface of the body..
Again, the CDC got their genital herpes numbers form the NCHS and NHANES, which got them by giving blood tests for HSV-2. It never applied any of the HSV-1 to genital infections, nor did it document the actual location of any of the infections, type 1 or 2.
So technically they can say “16.2% have HSV-2”, but claiming 16.2% (or any %) “have genital herpes” isn’t really going to be a very accurate depiction of Genital Herpes prevalence. There are a whole bunch of people out there who are infected with HSV-1 genitally who were never included in the “genital herpes” numbers. Many studies indicate half or more of genital infections are HSV-1 and in some studies – particularly in younger age groups – it’s been quite a bit higher than half. One study in Madison found 78% of new genital herpes infections were HSV-1. In that study, it actually was all the people who came in to student health, over a period of some years, to have genital sores diagnosed. They were all swabbed and cultured for both types of HSV and the data was recorded. Because of this, they know it was genital herpes and they know many had which type.
That doesn’t mean the CDC’s numbers are garbage; they aren’t. In addition, they did qualify their statistics, stating specifically that they were “seroprevalence” – prevalence of the antibodies in the blood – but not everyone who reads the website understands that, or realizes that someone can even GET HSV-1 qenitally, or realizes that none of the HSV-1 genital infections are included in the statistic. That last jump from “seroprevalence” to “genital”… and allowing people to believe that this was ALL the genital herpes infections.
That part could improve and they are working on that. We’ve seen the language being cleaned up and clarified quite a bit over the past year.
Got a question for us?