Sunday, 15 May 2016

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/