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Likewise, detectable RNA/DNA does not mean there's virus (virions). An unusual example, but it's common to have Ebola virus RNA in semen (a fluid from another

Likewise, detectable RNA/DNA does not mean there's virus (virions). An unusual example, but it's common to have Ebola virus RNA in semen (a fluid from another immuno-privileged site) with no detectable virus for months after primary infection. (https://www.nejm.org/doi/full/10.1056/nejmoa1511410 https://www.nejm.org/doi/full/10.1056/nejmoa1511410 among others.) Similar patterns exist for lots of other viruses.

XalvinX 8y ago
So why don't they try to isolate the virus itself instead of looking for RNA/DNA? Too expensive? Or impossible perhaps?
- zbjornson 8y ago
  Realistically, probably because they're not virologists. Looking for nucleic acids is easy/commonplace. Virus culture, electron microscopy and immunoassays are more specialized techniques.
  - XalvinX 8y ago
    If they aren't virologists, maybe they should leave this kind of research to those that are? The headline says "Researchers Find Herpes Viruses" ...but they didn't (or cannot?) find them? Then, umm...why does it say that?
- virusduck 8y ago
  This is more difficult than is sounds. Herpesviruses are quiescent (latent) for much of their lives and exist only as DNA, with no virions being produced. There are different latency "programs"--during some of these, there may be a handful of virus genes produced, and some there are no genes produced. Circumstances may cause these virus genomes to reactivate--transcribing genes and making virions. Maybe confusingly, herpesviruses may still contribute to the biology of the cell even in the latent state. DNA/RNA sequencing is also more sensitive in some ways (which can be both good and bad). It is also a very broad tool. You can go back to large datasets and try to squeeze more information out--even things you werent looking for originally, like herpesviruses. NCBI also hosts a very large repository of raw sequence data (SRA--the sequence read archive). Much of this data has decent metadata, so you could conceivably even do a new study on somebody else's old data.
virusduck 8y ago
True, but keep in mind: It is a normal part of all herpesviruses to be quiescent. They have the capacity to reactivate from nothing but their genome into a fully functional virus. Ebola is a negative-stranded RNA virus, and it is unlikely to find naked RNA in any body site. Rather, it is a mix of infectious virions and noninfectioius virus-like particles. The NEJM study you site was a qRTPCR only study. There was no attempt to actually culture the virus from the semen. Previous studies have tried culturing, and it difficult to culture semen-derived virus at the qRTPCR titers identified here.

XalvinX 8y ago

So why don't they try to isolate the virus itself instead of looking for RNA/DNA? Too expensive? Or impossible perhaps?

zbjornson 8y ago
Realistically, probably because they're not virologists. Looking for nucleic acids is easy/commonplace. Virus culture, electron microscopy and immunoassays are more specialized techniques.
- XalvinX 8y ago
  If they aren't virologists, maybe they should leave this kind of research to those that are? The headline says "Researchers Find Herpes Viruses" ...but they didn't (or cannot?) find them? Then, umm...why does it say that?
virusduck 8y ago
This is more difficult than is sounds. Herpesviruses are quiescent (latent) for much of their lives and exist only as DNA, with no virions being produced. There are different latency "programs"--during some of these, there may be a handful of virus genes produced, and some there are no genes produced. Circumstances may cause these virus genomes to reactivate--transcribing genes and making virions. Maybe confusingly, herpesviruses may still contribute to the biology of the cell even in the latent state. DNA/RNA sequencing is also more sensitive in some ways (which can be both good and bad). It is also a very broad tool. You can go back to large datasets and try to squeeze more information out--even things you werent looking for originally, like herpesviruses. NCBI also hosts a very large repository of raw sequence data (SRA--the sequence read archive). Much of this data has decent metadata, so you could conceivably even do a new study on somebody else's old data.

virusduck 8y ago

True, but keep in mind: It is a normal part of all herpesviruses to be quiescent. They have the capacity to reactivate from nothing but their genome into a fully functional virus. Ebola is a negative-stranded RNA virus, and it is unlikely to find naked RNA in any body site. Rather, it is a mix of infectious virions and noninfectioius virus-like particles. The NEJM study you site was a qRTPCR only study. There was no attempt to actually culture the virus from the semen. Previous studies have tried culturing, and it difficult to culture semen-derived virus at the qRTPCR titers identified here.