Saturday, 6 February 2016

Urine found to contain infectious Zika virus...again...

In what is becoming a trend of "part-of-the-story" science releases from Brazil's Zika virus (ZIKV) epidemic, we saw an overnight media report of the "first" finding of infections ZIKV in urine and saliva samples.[1,2]

It was not the first in urine. 

There was an earlier report from 2014 that described RNA and infectious virus in the urine of a Canadian traveller who had returned from Thailand, where she presumably acquired her ZIKV infection.[3]

Rushing out appallingly weak stories into scientific journals that exhibit very little peer review [4] and poorly worded or  thought out statements to describe ZIKV findings is not helping the situation in Brazil. In particular, it is doing nothing to investigate the link between ZIKV infection and congenital malformations or Guillain Barre syndrome. At all. 

I urge that everyone take a deep breath and perhaps involve a lot more more peer review - even for media releases.

And on the use of urine, just because previous studies have not sought infectious ZIKV (or other viruses) using culture techniques, or have not found it when they did look,[5,6] is not reason not rule out urine or any fluid as possibly contained infectious virus. When RNA is detected but RT-PCR, there is a real risk of infectious virus being present and there is a decent chance that culture will fail to detect that because it isn't a hugely sensitive technique at times and because of the many infectivity-degrading specimen handling steps between collection and culture. 

Whether that RNA detection, or this infectious virus detection for that matter, equates with an "infectious dose" of virus (enough virus to start an actual infection before the body's defences contain the virus) is the next issue to consider. Also, would mucous membranes onto which virus-contaminated saliva might be propelled, have the receptors to bind virus and the cells to support ZIKV replication? More questions.

Seriously though, has Ebola taught research studies nothing? Look everywhere and expect everything.

References...

  1. https://agencia.fiocruz.br/fiocruz-detecta-presenca-de-virus-zika-com-potencial-de-infeccao-em-saliva-e-urina
  2. http://edition.cnn.com/2016/02/05/health/zika-urine-saliva/index.html?sr=fbcnni020516zika-urine-saliva0438PMStoryGalLink&linkId=21012904
  3. First case of Zika virus infection in a returning Canadian traveler.
    http://www.ncbi.nlm.nih.gov/pubmed/25294619
  4. Ophthalmological findings in infants with microcephaly and presumable intra-uterus Zika virus infection
    http://www.scielo.br/pdf/abo/v79n1/0004-2749-abo-79-01-0001.pdf.
  5. Detection of Zika virus in urine.
    http://www.ncbi.nlm.nih.gov/pubmed/25530324
  6. Value of Routine Dengue Diagnostic Tests in Urine and Saliva Specimens
    http://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0004100
  7. Detection of Zika virus in saliva.
    http://www.ncbi.nlm.nih.gov/pubmed/26071336