The Q&A: WHO declares Zika outbreak a global emergency – five key questions

The World Health Organisation (WHO) declared the outbreak of Zika virus infections, and their suspected links to serious birth defects, a ‘public health emergency of international concern’ on February 1. The announcement will inevitably bring more attention to the issue and raises a number of pressing questions, including…

Why the sudden focus on the Zika virus?

The Zika virus was first discovered in Africa in the 1940s and is transmitted to people through the same mosquitos that is known to carry other flaviviruses like dengue, chikungunya and yellow fever. There have been sporadic but largely isolated Zika outbreaks over the years, but it was successively larger ones in French Polynesia in 2013 and more recently in Brazil last year that motivated health authorities to take a more serious look at the problem.

Amesh Adalja, a clinical assistant professor of emergency medicine at the University of Pittsburgh School of Medicine, told FirstWord that 80 percent of people who get infected with the Zika virus never show symptoms, and most of those who do experience only mild, self-limited effects like headache, skin rashes and fever that often last less than a week before the virus is cleared from the body naturally.

The real concern is the impact the virus may have on pregnant women. Indeed, what has attracted so much recent attention has been the sudden surge in babies being born with neurologic problems like microcephaly, a congenital condition characterised by incomplete brain development that leads to disability and shorter lifespans, which has accompanied the rise in last year’s Zika virus outbreak in Brazil.

Margaret Chan, WHO director general, noted in a press conference on February 1 that a causal relationship between Zika virus infection during pregnancy and microcephaly is not yet scientifically proven, but the potential association is still problematic enough to constitute an “extraordinary event’ that is requiring of a coordinated international response.

What is being done to stop the spread of Zika?

According to David Heymann, executive director of communicable diseases at WHO, the only option for limiting the spread of the virus at the moment is by reducing mosquitoes by removing or modifying breeding sites and limiting the contact between humans and insects by using insect repellent, bug nets and long clothing.

The first step now is to conduct a coordinated surveillance of regions in which the outbreak has occurred to better understand whether (and if so how) the Zika virus causes developmental disorders like microcephaly. Unfortunately the low-level virulence and largely asymptomatic nature of those who are infected will hinder the process, which highlights the need for the immediate development of faster and better diagnostics to replace the current standard of polymerase chain reaction testing and virus isolation from blood samples.

What preventative and/or therapeutic efforts are in development?

The unfortunate truth is that the cupboard is essentially bare when it comes to drug and vaccine candidates to treat or prevent Zika virus infection.

“Zika was something that did not seem to affect that many people, and those who were symptomatic experienced only minor problems,” remarked Adalja. “It was not something that anyone thought could cause an outbreak of major public health significance, so there just isn’t anything in the pipeline as far as drugs or vaccines go.”

However, the fact is that the Zika virus is not a good candidate for developing antivirals against because so many of those infected are asymptomatic, meaning that the best approach for drugmakers is likely going to be to come up with a vaccine against the virus.

“Vaccine development is a notoriously long process that usually takes a number of years, and unfortunately people may have gotten the wrong impression from the recent Ebola outbreak” where vaccines were ready for human testing soon after it became a public health emergency, noted Adalja. In fact, those vaccines had been in the works for years at that point, and it just so happened that they were approaching the clinic at the right time.

The same cannot be said of the Zika virus, where the only company that has come out and said it is already working on a vaccine is Inovio Pharma, which along with partner GeneOne is preparing to graduate a DNA-based vaccine from testing in mice to non-human primates.

It should be noted that there are some innovative strategies being tried, including a genetically modified type of mosquito being developed by a subsidiary of Intrexon that spawn only male offspring that reportedly do not bite humans.

What can industry do to speed up development efforts?

The attention that health authorities and governments are now dedicated to respond to the Zika outbreak should free up some resources that can be dedicated towards developing diagnostics and vaccines, though some experts have warned that it can sometimes take a decade to develop a vaccine from start to finish.

Adalja noted that one possible shortcut of sorts that could be tried is by taking a vaccine that was developed for another flavivirus, for example one for dengue or West Nile, and inserting a gene for Zika.

In December, Sanofi received approval to begin marketing Dengvaxia in Mexico, making it the first ever vaccine to be approved anywhere in the world to prevent dengue. The French drugmaker did not respond to an inquiry about whether it was studying the possibility of leveraging this product to speed the development of a Zika vaccine.

Has the recent Ebola outbreak had an impact on the response?

Adalja suggested that one silver-lining of the recent Ebola outbreak in Africa is that public health authorities like the WHO and national governments are more acutely aware than ever before of the importance of acting quickly and doing so in coordinated fashion to try and head off an outbreak before it can become an epidemic.

Ebola and Zika “are totally different viruses causing very different problems in different parts of the world, so the type of response will inevitably need to be different,” said Adalja, “but in general the willingness of public health agencies to be more proactive and less reactive, and to really think about the full trajectory of an outbreak at an early stage” are silver linings of sorts from the recent Ebola experience.

“Today's announcement will focus attention and resources on understanding the potential link between severe disease and Zika, as well as on attacking the mosquito responsible for its spread,” he added.

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