Monday, April 18, 2016

Fiocruz: Revisting Zika Virus Detection In Saliva & Urine


Just over three months ago sexual transmission of the Zika virus was considered a rare - almost theoretical - possibility.  There had been one documented case (see Probable Non–Vector-borne Transmission of Zika Virus, Colorado, USA) back in 2008, involving two researchers infected in Africa, one of whom returned to the United States and passed the virus (presumably via sexual contact) to his wife.

To date the United States has identified at least 7 sexually transmitted cases, including both male-to-female and male-to-male transmission, and internationally we are hearing of additional cases every week. 

While believed a minor component in the chain of transmission, Zika is gaining a reputation as being an STD (see CDC : Sexual Transmission Of Zika May Be More Common Than Previously Believed), and the CDC has released comprehensive guidance on the prevention of sexual transmission.

Although unproven as a route of transmission, two months ago researchers reported finding both live Zika virus and Zika RNA in both saliva and urine (see FIOCRUZ: Statement On Detection Of Zika Virus In Saliva and Urine).

Another study, appearing in Eurosurveillance: Prolonged Shedding Of Zika Virus RNA In Saliva - Italy in early March, also reported on the detection of both live virus and viral RNA, and suggested their findings  pose questions on the potential risk of human-to-human transmission of the virus through saliva.

It is still pretty much theoretical, as doctor's haven't identified any cases, and we don't even know if the viral load in an infected person's saliva is sufficient to infect someone else.

Bringing us up to date on their research, FIOCRUZ - one of the oldest and most prestigious scientific research institutes in South America - published an update on their findings last Friday.  I've only included some excerpts, follow the link to read it in its entirety.

Publication details finding Zika virus with potential for infection in saliva and urine

The unprecedented identification of particles Zika virus with potential for infection in saliva and urine samples from two patients, announced in February, warned of the possibility of other routes of transmission of the disease, in addition to already known.
Led by the Instituto Oswaldo Cruz (IOC / Fiocruz) in partnership with the National Institute of Infectious Diseases Evandro Chagas (INI / Fiocruz), research has just had complete data disclosed. The study shows that the active virus were found between the samples with the highest viral loads. Furthermore, there is evidence that in urine samples with acid pH, the amount of infective virus particles is reduced or nonexistent.
Research also shows the complete genetic sequence of the active Zika virus isolated from a sample of saliva and urine another. The analysis showed that the two strains belong to the Asian lineage and are very similar to other Zika virus sequenced in Brazil and countries of the Americas recently.

The researchers note that further studies are needed to investigate the epidemiological relevance of possible alternative routes of infection Zika virus through urine or saliva. According to Myrna Bonaldo, head of the Molecular Biology Laboratory of Flavivirus IOC and one of the coordinators of the work, there are few reports in the literature on the presence of assets of the Flavivirus genus virus - including Zika and dengue, among others - samples like these .
"The dengue virus and Zika himself had been found in saliva and urine, but not in the infective form. In urine, the excretion of the West Nile Fever virus, which is also a Flavivirus, with a potential of infection had been registered, but still knows little about the potential transmission of this pathway. In the case of Zika, many studies are needed to understand the impact of the presence of active viral particles in these samples, "says the researcher.

Following the commitment of immediate dissemination of scientific findings related to international public health emergency caused by Zika virus, the article was published on the website 'bioRxiv', which provides online studies prior to publication in scientific journals. The work included the participation of researchers from the Molecular Biology Laboratory of Flavivirus and Mosquitos hematozoa Transmitters IOC, Febrile Diseases Laboratory Agudas the INI and the National Laboratory for Scientific Computing (LNCC).  
(Continue . . . )

Trying to isolate sexual transmission in an environment where there are active mosquito vectors is all but impossible.  Sexual transmission only became apparent once cases were exported to regions without a competent vector.

With a relatively small cohort of sexually transmitted cases available for study, trying to parse out exactly what kind of intimate contact led to the infection of their partner will be similarly difficult. 

While transmission via saliva seems like a long shot today, the Zika virus has consistently demonstrated a blatant disregard for conventional wisdom.  Arboviruses aren't supposed to cause birth defects, or be transmitted sexually, either.  

Reminding us we should hardly ever say `never'.

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