Colombia Zika virus report, Epidemiological Week No. 18...

The latest epidemiological report, which includes data on Zika virus disease (ZVD; 01MAY2016-07MAY2016), has been produced by the Colombian National Institute for Health team.[1]

Graph No.1. The cumulative curve of confirmed ZVD cases 
(green circles, left-hand axis) and the change in confirmed ZVD case 
numbers when compared to the preceding week's total 
(green bars, right-hand axis). Data from [1]. 
Click on graph to enlarge.

Graph No. 1 shows that 1,116 more laboratory confirmed cases of ZVD were reported this week than last. That's the biggest weekly rise on record. The total now at 4,867 or 7% (reaching the highest proportion reported to date) of all the clinically suspected Zika virus (ZIKV) detections.

Graph No.2. The cumulative curve of suspectedZVD cases
(pink circles, left-hand axis) and the change in suspected ZVD case
numbers when compared to the preceding week's total
(red bars, right-hand axis). Data from [1].
Click on graph to enlarge.

Graph No. 2 shows the change in suspected cases. These are not laboratory confirmed. The suspected ZVD cases continue to rise in a linear fashion, adding 2,665 this week to total 71,299 suspected cases of ZVD. This is far from the biggest weekly rise suggesting the figure above may indicate more testing or improved laboratory capacity or reporting (clearing a backlog?).

Graph No.3. The cumulative curve of confirmed ZIKV infections 
(lilac circles, left-hand axis) and the change in confirmed ZIKV infection 
numbers when compared to the preceding week's total 
(purple bars, right-hand axis). Now added the reported umber of microcephaly cases 
confirmed as ZIKV infected (yellow bars, right-hand axis). To account for adjustments 
that take cases away when there is no weekly case growth, a negative 
value - the y-axes now allow for negative values. Data from [1]. 
Click on graph to enlarge.

Graph No. 3 shows that to Epidemiological Week No. 18, 11,417 suspected (-307 compared to last week) and 2,948 confirmed ZIKV infections (+941 - biggest rise to date) have been identified in pregnant women. 

As of this report, 5 (same as last week) live births have been diagnosed with microcephaly/central nervous system disorders and were reported as being ZIKV positive; 43 (up from 32 last week-fourth week to increase in total number) other microcephaly diagnoses are now under investigation.[1] That represents 0.17% of all confirmed ZIKV positive mothers (down from 0.25% last week).

It has now been 210 days, or about 7 months, since ZIKV was first confirmed in Colombia on 16th October 2015.[2] Colombia is currently carrying the next biggest load of Zika virus disease cases, after Brazil.[3] Keep in mind that when talking about microcephaly - we have to think back in time to what insult or infection might have occurred in the first or second trimester. The counts of virus occurring this week will have zero impact on what happened back then.

Brazil first reported reported positive (but unconfirmed) laboratory tests for Zika virus disease on 29th April 2015. Brazil then started to report a rise in foetal anomalies (an initial 141), in the form of microcephaly on 30th October 2015. This was 184 days - or about 6 months later.[4]

References...

1. http://www.ins.gov.co/boletin-epidemiologico/Boletn%20Epidemiolgico/2016%20Boletin%20epidemiologico%20semana%2018.pdf
2. http://www.who.int/bulletin/online_first/16-171082/en/
3. http://www.nature.com/news/first-zika-linked-birth-defects-detected-in-colombia-1.19502
4. http://who.int/bulletin/online_first/16-171082/en/

Colombia Zika virus report, Epidemiological Week No. 17...

The latest epidemiological report, which includes data on Zika virus disease (ZVD; 24APR2016-30APR2016), has been produced by the Colombian National Institute for Health team.[1]

Graph No.1. The cumulative curve of confirmed ZVD cases 
(green circles, left-hand axis) and the change in confirmed ZVD case 
numbers when compared to the preceding week's total 
(green bars, right-hand axis). Data from [1]. 
Click on graph to enlarge.

Graph No. 1 shows that 1 fewer laboratory confirmed case of ZVD was reported this week than last. That's different. The total now at 3,751 or 5% of all the clinically suspected Zika virus (ZIKV) detections.

Graph No.2. The cumulative curve of suspectedZVD cases
(pink circles, left-hand axis) and the change in suspected ZVD case
numbers when compared to the preceding week's total
(red bars, right-hand axis). Data from [1].
Click on graph to enlarge.

Graph No. 2 shows the change in suspected cases. These are not laboratory confirmed. The suspected ZVD cases continue to rise in a linear fashion, adding 2,671 this week to total 68,634 suspected cases of ZVD.

Graph No.3. The cumulative curve of confirmed ZIKV infections 
(lilac circles, left-hand axis) and the change in confirmed ZIKV infection 
numbers when compared to the preceding week's total 
(purple bars, right-hand axis). Now added the reported umber of microcephaly cases 
confirmed as ZIKV infected (yellow bars, right-hand axis). To account for adjustments 
that take cases away when there is no weekly case growth, a negative 
value - the y-axes now allow for negative values. Data from [1]. 
Click on graph to enlarge.

Graph No. 3 shows that to Epidemiological Week No. 17, 11,724 suspected (+418) and 2,007 confirmed ZIKV infections (-1) have been identified in pregnant women. 

As of this report, 5 (an increase (+1) from last week) live births have been diagnosed with microcephaly/central nervous system disorders and were reported as being ZIKV positive; 32 (up from 26 last week) other microcephaly diagnoses are now under investigation.[1] That represents 0.25% of all confirmed ZIKV positive mothers.

It has now been 207 days, or about 7 months, since ZIKV was first confirmed in Colombia on 16th October 2015.[2] Colombia is currently carrying the next biggest load of Zika virus disease cases, after Brazil.[3]

Brazil first reported reported positive (but unconfirmed) laboratory tests for Zika virus disease on 29th April 2015. Brazil then started to report a rise in foetal anomalies (an initial 141), in the form of microcephaly on 30th October 2015. This was 184 days - or about 6 months later.[4]

References...

1. http://www.ins.gov.co/boletin-epidemiologico/Boletn%20Epidemiolgico/2016%20Bolet%C3%ADn%20epidemiol%C3%B3gico%20semana%2017.pdf
2. http://www.who.int/bulletin/online_first/16-171082/en/
3. http://www.nature.com/news/first-zika-linked-birth-defects-detected-in-colombia-1.19502
4. http://who.int/bulletin/online_first/16-171082/en/

The three parent hypothesis: Mum, Dad and Zika virus...

Ian M. Mackay & Katherine E. Arden

This week we saw a case study of a 32 year old man returning from Brazil to France who recovered from a Zika virus (ZIKV) infection.[1] Nothing to see there. 

But there was something fascinating to see when the authors pointed us to the viral loads in samples collected 2 weeks after symptom onset...

• Serum: 10^2.8 copies of viral RNA per millilitre of sample (about 631 copies/ml)
• Urine: 10^3.1 copies/ml (=1259 copies/ml)
• Semen: 10^8.6 copies/ml (=398,107,171 copies/ml)

Semen had 630,914-times more ZIKV RNA in it than serum (316,209 times more than urine) - two weeks later! And in addition to the detection of viral RNA, infectious ZIKV could be isolated using cell culture of the semen sample.

Not only was there so much more viral RNA in semen than in urine or serum, but serum remained positive 2 weeks later. That is not the norm for a ZIKV infection. Usually, viraemia (virus, or viral RNA as a surrogate for virus, in the blood) resolves within a week.[2] That suggests that in some people, ZIKV can replicate very efficiently and for a longer time than what we consider to be the average. Could this be something to do with the nature of the particular ZIKV variant of the Asian lineage circulating in Brazil? Is it just showing up because there are more cases than we've seen before. It does - yet again - flag how much we need more testing data and publications of quality from Brazil. We also really need some comparative virology studies, and more sequencing. Key puzzle pieces that are still missing.

Sexual transmission of ZIKV is rare but, as we've seen described a number of times now,[3] it is a plausible route of infection. It may also be possible that an infectious dose - currently not defined - is delivered via the semen of even low viral load mildly ill or asymptomatic men; assuming that lower viral loads correlate with few or no symptoms and assuming that there is any ZIKV in the semen of men with mild signs and symptoms, or none at all. This may lead to an infection in the partner.

What if... a ZIKV infection in the female partner leads to a foetus with congenital anomalies that begins at fertilization? What if there are in fact 3 players at conception; Mum, Dad and Zika present in the semen?

Among those studies which hopefully aim to go beyond the "scientific consensus" and use actual science to logically seek some real evidence, it would be great to see them answer:

1. What is the serostatus of the mother and father for DENV, CHIKV and ZIKV before conception?
2. Is Dad's semen positive for DENV, CHIKV or ZIKV prior to conception?
3. How do antibody levels to DENV, CHIKV and ZIKV vary during the course of the pregnancy?

It is worth considering the other two viruses, DENV and CHIKV because there has been no investigation into whether they, or cellular or antibody immune responses to them, may interact to produce the foetal anomalies seen in Brazil and French Polynesia. These three viruses have all been active at some time in these regions-sometimes at the same time.

Some things to at least consider.

References...

1. http://www.thelancet.com/pdfs/journals/laninf/PIIS1473-3099(16)00138-9.pdf
2. http://virologydownunder.blogspot.com.au/2016/04/usefulness-of-urine-samples-for-zika.html
3. Sexual transmission of Zika virus: implications for clinical care and public health policy
   http://www.ncbi.nlm.nih.gov/pubmed/27048746