Sunday, 4 December 2016

Zika virus-positive microcephaly in Colombia...

The latest epidemiological report (epidemiological week 47) from Colombia, which includes data on Zika virus (ZIKV) disease (ZVD; 20NOV2016-26NOV2016), has been produced by the Colombian National Institute for Health team.[1]
NOTE: While these data were reported the past epidemiological week (EW), they may not be from that week. See earlier post about possible reporting lag.

As of this report, 60 (+0 from last EW) live births have been diagnosed with congenital ZIKV syndrome (CZVS; microcephaly/central nervous system disorder), confirmed as being ZIKV positive. That represents 1.0% of all confirmed ZIKV positive mothers-a slowly but steadily rising proportion.

The change in confirmed ZIKV infection numbers when detected in
association with a microcephaly diagnosis, Colombia, compared to the
preceding week's total (yellow bars, right-hand axis). Those diagnoses still in question and under investigation are shown as yellow dots (left-hand axis).
Data are from [1]. 
Click on graph to enlarge.
It has now been 415 days, or 1 year, 1 month and 18 days, since ZIKV was first confirmed in Colombia on 16th October 2015.[5] Keep in mind that when talking about microcephaly - we have to think back in time to what insult or infection might have occurred during pregnancy. The counts of ZIKV occurring this week will have zero impact on what happened back then. Also keep in mind that Colombia may be reporting things differently from Brazil.[3]

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.

No new laboratory confirmed ZIKV detections have been reported in Colombia for eh 20th week (green graph, above).


Brazil first reported positive (but unconfirmed) laboratory tests for ZIKV 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] However, the genetic analyses suggest ZIKV was in Brazil from around 2013. It had a lot longer to get established. Perhaps this is the difference between Brazil and Colombia, given reports a growing 2,180 ZIKV congenital syndrome diagnoses [2] compared to Colombia's 60.

References...

  1. http://www.ins.gov.co/boletin-epidemiologico/Boletn%20Epidemiolgico/2016%20Bolet%C3%ADn%20epidemiol%C3%B3gico%20semana%2047.pdf
  2. http://www.paho.org/hq/index.php?option=com_docman&task=doc_view&Itemid=270&gid=37143&lang=en
  3. http://virologydownunder.blogspot.com.au/2016/06/the-elephant-squeaked.html
  4. http://www.paho.org/hq/index.php?option=com_docman&task=doc_view&gid=35139&Itemid=270&lang=en
  5. http://www.nejm.org/doi/full/10.1056/NEJMoa1604037#t=article