For the vast majority of people, Zika virus infection, spread by the bite of an infected mosquito, causes a very mild disease; serious complications and deaths from Zika are not common. However, recent increases in congenital anomalies, particularly microcephaly (where the brain does not develop properly resulting in a smaller than normal head) and Guillain-Barré syndrome (a rare and serious condition of the peripheral nervous system) and other neurological and autoimmune syndromes, are being reported in areas where active Zika transmission has been confirmed.
I am the Scientific and Operational Lead for the National Collection of Pathogenic Viruses (NCPV), within PHE. We maintain stocks of clinically important viruses, and supply them to scientific researchers. NCPV supplies frozen cultures of Zika virus and RNA extracted from Zika virus to research laboratories across the world.
Since the WHO declared that the Zika virus outbreak in South America is a Public Health Emergency of International Concern, PHE’s Culture Collections are responding to numerous enquiries about the supply of this Zika virus strain every day. NCPV monitored the developing epidemic in Brazil during 2015 and ensured that stocks of Zika virus would be available should the situation worsen. We are continuing to monitor the situation, and will restock as necessary, in response to this sudden spike in research demand.
When a new disease emerges, or levels increase like this, research is needed to understand the pathology of disease, develop diagnostic tests, and potentially ultimately develop vaccines or medicines. This important research is carried out by universities, private companies, and government agencies. But what research is going on at the University of Southampton to help tackle the spread of the disease?
The University’s ‘WorldPop’ is a population mapping project that provides open access spatial demographic datasets to support development, disaster response and health applications.
Our analyses suggest that an estimated 1.67 million childbearing women in Central and South America could become infected by the Zika virus by the end of the first wave of the epidemic.
With our collaborators from the University of Notre Dame in the US and the University of Oxford, we have also found that across Latin America and the Caribbean over 90 million people in total could become infected before the first wave of the epidemic concludes.
Our projections are an important early contribution to global efforts to understand the scale of the Zika epidemic, and provide information about its possible magnitude to help allow for better planning for surveillance and outbreak response, both internationally and locally.
Scientists have now confirmed the link between microcephaly in babies and Zika. However, it is difficult to accurately predict how many childbearing women may be at risk because a large proportion of cases show no symptoms. This largely invalidates methods based on case data and presents a formidable challenge for scientists trying to understand the likely impact of the disease on populations
However, we have been investigating the spread of the disease by examining its likely impact at very local levels – at a scale of five kilometres squared – to model infection rates across the region.
We took into account disease patterns displayed in similar epidemics, along with other factors such as how the virus is transmitted (in this instance by mosquito), climate conditions and virus incubation periods. We also examined transmission behaviour in dengue and chikungunya viruses, which are spread by the same mosquitos. Our projections for Zika are largely consistent with annual, region-wide estimates of 53 million infections by the dengue virus (2010), which has many similarities to Zika.
Coupled with existing data on population, fertility, pregnancies, births and socio-economic conditions for the region, we have been able to model the scale of the projected spread of the Zika virus and provide a detailed understanding of the places likely to be most affected – helping to inform policy and planning on which areas will need the most support in combatting the disease and helping sufferers.