Where next for Zika?

Since the outbreak of the Zika virus last year in Brazil and the revelation that infection of pregnant women can lead to severe birth defects the WHO declared the spread of this disease a global emergency. Zika has spread across the Americas with a high number of cases now being reported in Florida; though most of these are travel-related local transmission accounts for over 60 cases in the state. The recent appearance of the disease in Asia includes over 300 cases reported in Singapore, 100 in Thailand and the emergence of the disease in the Philippines and Malaysia with some of these cases including pregnant women.

A new paper (link is external) published in the Lancet has examined the travel, climate and mosquito patterns across different countries in an attempt to predict the path of the Zika.  From these calculations a potential 2.6 billion people could be at risk from Zika infection, with some of the most vulnerable countries being India, China, the Philippines, Indonesia, Nigeria, Vietnam, Pakistan and Bangladesh. Highlighting the potential for a Zika outbreak in these countries could help those with limited resources to manage these resources as efficiently as possible in order to avoid the worst effects of Zika. The lack of knowledge around whether any immunity exists from potential previous exposure in these populations means that infection rates might not reach these levels, but we can’t be sure.

Genome sequence analysis of at least two Zika virus samples in Singapore (link is external) show that the virus strain there more closely resembles the form of Zika that has circulated in Southeast Asia since the 1960s than that which is rife across the Americas. This suggests a level of immunity might exist in these populations that could curb a potential disease outbreak. But, there is a lack of understanding over what has fuelled the recent explosion in cases. We do not know whether specific mutations in the virus might have changed how it affects its human victims or whether other risk factors- such as infection with other diseases or other exposure- might somehow influence Zika’s severity, and this prevents us from adopting the most effective strategies to combat Zika infections.

Since the Zika outbreak the pace of researchers response over the past year has been amazing in developing understanding about the viral disease mechanisms, the routes of transmission, generating two candidate vaccines that are entering human trials and creating potential Zika diagnostic assays. At Avacta within just 13 weeks we were able to identify and characterise three specific Affimer binders to the secreted Zika virus NS1 protein for use in rapid point-of-care diagnostic tests, showing that our technology offers realistic response times to newly emerging diseases.

Zika mosquito

As with the Ebola outbreak before it Zika infection levels will wane, but unlike Ebola Zika infections are predicted to recur in synchronicity with the mosquito seasons. This means that the current wait for Zika diagnosis (link is external), in particular for pregnant women who wait to know if their unborn children may have been affected by the virus, are too long with many waiting weeks for results. Equally the current clinical trial pathway to establish the efficacy of infectious disease outbreak countermeasures needs addressing to bring potential treatments and vaccines to market quicker.

This may mean developing new trial designs, such as the ring-vaccination trial (link is external) used to test an Ebola vaccination, or adapting current designs (link is external) to meet the logistical challenges of a disease and the populations in which it is spreading. For Zika trials this has the added difficulty of monitoring infection in the trial participants, where the current serologic diagnostic tests are imperfect and there is a crucial need for Zika specific assays that can identify infection in individuals beyond the initial stages- a key reason we developed our Zika specific binders. 

Clearly we can’t foresee future disease outbreaks, so investing in disease specific drug and diagnostic research and development ahead of time is impossible. Yet the social, economic and political stress caused by these types of outbreaks is huge so our approach to identifying and developing diagnostics and therapeutics needs to be addressed. Adopting the correct technology that will allow us to quickly respond to stem the spread of potential pandemic diseases could be the best defence we have.