Perusing the literature I came across a discussion of a recent meta-analysis (a study of studies) performed by the US Centers for Disease Control and Prevention (CDC), looking into trying to better compile information on just how many viruses can live in human semen. If you are anything like me you are likely thinking... um ... why would I want to know that? You might even want to close this blog out, but... you'll be back. Just like I was when reading about this, because, you know... just HOW many viruses are known to be able to live there??

So lets take a brief moment to discuss the summary of the data that the CDC put together.

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Why Were The CDC Scientists Interested In Viruses In Semen In The First Place?

It's not a bad question to be asking. I mean... I asked it my self. However the answer is not unsurprisingly, pretty straight forward. Zika. A recent study reported that even after the symptoms of a zika virus infection subside, that Zika virus RNA was still detected in the semen of over 50% of the men they tested.

To make matters worse the virus was active meaning that Zika virus is a sexually transmittable disease (not new information).

To make matters even worse-er, the longest amount of time after the end of symptoms that Zika virus has been detected in semen was a whopping 62 days! [3]. Zika isnt the only terrifying active replicating virus that has been extracted from semen either, there is also our favorite bleed out of every orifice hemorrhagic fever causer, Ebola. [4] Yes, thats right. Ebola can also be a STD.

The CDC authors explain that the testes are just an imperfect barrier to viruses, especially when there is some inflammation, and it shouldn't be entirely surprising that the male reproductive tract finds itself a home for them. [5]

Okay... Thats...Yep, They Should Be Compiling All The Data On This...

So what about other viruses? Well the authors did an extensive literature search and identified 27 viruses that were found in human semen.

In the article they list all of these viruses in a Table. However briefly, some are ones you would expect (HIV, Hepatitis C, a smattering of various Herpes viruses) but others are a little more surprising! For example there is evidence that the Mumps virus can be found in semen.

One observation the CDC authors made was that the viruses which have, to this point, been identified in semen come from very diverse classes. They point out that this means that there isn't a specific aspect (like the shape of the virus, or type of genome, or surface receptors etc etc etc) that makes a virus better able to get into semen.

They also point out that the majority of studies reporting on this were looking only at the presence of viral genetic material. These studies do not indicate whether or not these viruses are actively replicating, or are transmissible (unlike what was reported for ebola as discussed above).

This does bring up a few questions though:

• How many of these viruses are actually active?
• Could they be transmitted? If so for how long after an infection is this possible?
• Is transmission possible to say a growing fetus? Could transmission of these viruses be a potential cause of miscarriages?

None of this is known, but its quite clear that there is a need to investigate it. As the answers could be quite impactful, and may even lead to significant improvements in successful pregnancy (IE if transmission of a virus like this can cause a miscarriage then that could be avoided).

Other Random Tidbits of Information from the Article

• Influenza (the cold virus) has been found in human testicles, could it wind up in semen? Could it be transmissible sexually? That would be a really weird way for someone to catch a cold.

• Viruses may make men more susceptible to other STD infection as they could increase inflammation in the reproductive tract.

CDC Author Conclusions

There may be a heck of a lot more viruses that are present in human semen, certainly a lot more then we know now, and a lot more then one would expect. The authors state that further testing to identify whether viruses with a high chance to cause death or other severe health issues are possibly present would be potentially beneficial for public health.

My Takeaway

There are a surprising number of viruses that could potentially be found in semen, including many that I at least would not associate with sexual transmission.

My Other Takeaway

Condoms might just be protecting our partners from more than just STD's (and unwanted children)...

Sources

Text Sources

1. https://wwwnc.cdc.gov/eid/article/23/11/17-1049_article
2. https://wwwnc.cdc.gov/eid/article/23/4/16-1692_article
3. http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=22554
4. http://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0004475

Image Sources

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