Sunday, 19 June 2016

Colombia Zika virus report, Epidemiological Week No. 23...

The latest epidemiological report from Colombia, which includes data on Zika virus disease (ZVD; 05JUN2016-11JUN2016), has been produced by the Colombian National Institute for Health team.[1]
NOTE: While these data are from those reported the past epidemiological week, they may not be from that week. See earlier post about possible reporting lag.


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 zero new laboratory confirmed cases of ZVD were reported this week-this must be an "off" week for laboratory reporting - you can see others in the above graph where the green bars sit at zero. The total still rests at 8,221 or 10% (the highest proportion reported to date) of all clinically suspected Zika virus (ZIKV) detections.
Graph No.2. The cumulative curve of suspected ZVD 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 2,086 this week to total 85,021
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. 23, 10,704 suspected (+268 compared to last week) and still 5,420 confirmed ZIKV infections (+zero-no lab results this week) have been identified in pregnant women.

As of this report, 6 (+0 from last 2 weeks) live births have been diagnosed with microcephaly/central nervous system disorders and were reported as being ZIKV positive; 81 (up from 69 last week and the highest value to date - could things be picking up pace?) other microcephaly diagnoses are now under investigation.[1] That represents 0.11% of all confirmed ZIKV positive mothers. 

Graph No. 4 below focuses on just these ZIKV-positive cases and those that remain under investigation, highlighting how the investigatory total has changed each week, but has also been trending upwards since Epidemiological Week No. 14. This may be a marker of a rise in microcephaly and other congenital disorders.
Graph No.4. The change in confirmed ZIKV infection numbers
when detected in association with a microcephaly diagnosis, compared
to the preceding week's total (yellow bars, left-hand axis). Data are from [1].
Click on graph to enlarge.
It has now been 247 days, or 8 months 3 days, 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 (probably-still not definitive). The counts of virus occurring this week will have zero impact on what happened back then. Also keep in mind that Colombia may be reporting things different from Brazil.[5]

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]