For the second time, US CDC declares publicly that Zika virus causes microcephaly (M) and other Central nervous system diseases (CD):13% of zika tested positive could lead to microcephaly if occurring at the early stage of pregnancy (<3 months).
In his excellent blog, VDU’s blog, Pr Ian Mackay is monitoring epidemiological data coming from Brazil on a weekly basis. For his 27 report, week 20, he is pointing out that 15% of all confirmed M&CD diagnoses and 3% of all suspect diagnoses are reported as positive for ZIKV testing . Question: what are the causes of the 85 to 97% M&CD?
If we now refer to another paper on causes of microcephaly in Brazil, in Pernambuco State (2015), it is amazing to notice that based on a cohort of 104 newborns with microcephaly, we observe plenty of cases related to TORCH infection, some of them due to co-infection. It is mentioned that ZIKV test was not available at that time, between April and December 2015. Compared with previous records 2010-2014 with 7 cases/year, Brazil health authorities have recorded 874 cases in Pernambuco State in 2015. Taking into account that Zika outbreak started in April 2015 in Brazil with a peak around October, the question raised to consider Zika virus (alone) causing mincrocephaly. In this survey, Dengue does not appear to be a co-factor as suggested by other case review studies and confirmed by In Vitro experiments.
Saying that, it is obvious that 2015 recorded abnormal increase of microcephalies, especially in NE Brazil: 7 ->874 microcephalies (x125). If highly significant, the question behind is to understand the root causes, focusing on the role and responsibility of Zika virus. Cytomegalovirus and Rubella are the two main identified virus related to these microcephalies without the capability to link with Zika virus (not tested).
Last, not least, it remains an unclear statement with regards the use of pesticides/larvicides during the same period of time in the same region of Brazil. Notwithstanding, we have to address the question of huge differences in the numbers reported in NE compared with other regions in Brazil. At the end of the day, it remains a speculation of co-factors or co-infection acting jointly with Zika virus as causing microcephaly.