by Dr. Martin Forde, Sc.D., R.Eng
Zika is no Chikungunya. While many can vividly attest to the agony Chikungunya caused them — with some still suffering the painful effects many months later — for most persons who get the Zika virus they won’t even know it.
This is because for every 5 persons who get infected by the Zika virus, 4 of them will have no discernable symptoms. Whether this is due to them having a very strong immune system or the virus itself not posing a very significant challenge to most people’s immune defence systems, this means that over 80% of persons who get infected by Zika will be blissfully unaware of the fact. Indeed, the majority will continue to go about their merry way, unaffected and unperturbed.
This past Monday (1 February), however, the World Health Organization (WHO) convened an emergency meeting to review the severity of the health threat posed by the rapid spread of the Zika virus in Latin American and Caribbean (LAC) region.
What did they conclude? After reviewing all the data at hand, the 18 convened experts advised that this Zika outbreak constituted an “extraordinary event.” Further, they warned that it poses a serious public health threat to not only the LAC region, but to other parts of the world as well. To emphasize the seriousness of the situation, Dr Margaret Chan, the Director-General of the WHO, invoked the International Health Regulations and declared that the current LAC Zika outbreak was a Public Health Emergency of International Concern (PHEIC).
But why? As already suggested, Zika is a lightweight pugilist when compared to its two Mike Tyson cousins, the Chikungunya and Dengue viruses. Further, in the 20% of adults who do experience some sort of hit from the Zika virus, the damage will be mostly limited to a mild rash and slight fever. So again, why the need to declare a PHEIC?
Whereas Zika poses a relatively minimal threat to most healthy adults, the same cannot be said for the unborn child. Much of the motivation behind the WHO’s proclamation of a PHEIC due to the Zika outbreak is that increasing evidence is accumulating that this virus can cause the unborn child severe congenital malformations (such as a shrunken head) and neurological complications (a damaged brain), a condition called microcephaly.
The first ominous signs that Zika might be doing more than just make some adults uncomfortable for a few days came from startling observations several months into the Brazilian Zika outbreak. Since May of 2015, the number of reported microcephaly cases in Brazil increased 20-fold. Over the previous 5 years, from 2010 and 2014, Brazil reported an average of 163 microcephaly cases per year. However, in just the 9 months since the outbreak of Zika in Brazil, they have reported almost 4,000 cases, including 46 deaths.
Could this just be purely coincidental? After all, just because one observes two events occurring at the same time does not automatically mean that one causes the other or that they must be connected to each other in some way. To use the word epidemiologists employ to describe such evidence, they would say that the current evidence linking Zika to microcephaly is circumstantial. Nonetheless, as the dramatic increase in microcephaly cases in Brazil suggests, many have concluded that this circumstantial evidence is just too strong and pervasive to be simply dismissed as some quirky occurrence of happenstance.
It is thus understandable why the WHO in spite of the uncertainty surrounding whether Zika is primarily responsible for this dramatic surge in the numbers of microcephaly cases has decided to err on the side of caution and declare that the Zika outbreak is a PHEIC. A key benefit of doing so now it that this allows the WHO to launch a coordinated global offensive which hopefully will help bring increased clarity on answering what role, if any, Zika plays in the cause of microcephaly and other possible adverse health effects.
Given that the WHO estimates that over 4 million people could be infected by Zika by the end of this year, the stakes are pretty high to limit the damage this virus will wreck on the LAC region. Almost all LAC country populations are at heightened levels of risk since until now, almost no one in this region of the world has previously been exposed to Zika and so the majority have not developed any immune defence to fight it.
A key question that arises is what is the most appropriate response to take towards this virus outbreak. Given that the greatest identified risk at present is limited to the unborn child of pregnant women, several countries have decided that it is prudent to advise all women of childbearing age in their countries to delay pregnancy. In some cases, such as El Salvador, women are being advised to wait until at least 2018 before contemplating pregnancy.
While the WHO has stopped short of advising pregnant women not to travel to Zika affected countries, the Centers for Disease Control and Prevention (CDC) in the US has decided that it is most appropriate to advise pregnant women from their country not to travel to any of 24 LAC Zika infected countries.
One can debate whether the WHO or the CDC has got the right advising protocol for pregnant women, however, the following facts are worth keeping in mind. Firstly, there is no anti-Zika vaccine currently available. And as anyone who has lived in the tropics well knows, it is virtually, if not totally impossible, to completely avoid getting bitten by at least one mosquito. Thus, getting Zika from an infected mosquito is always going to be a very real possibility.
It is also worth noting that half of all pregnancies are unintended. Thus, if a woman becomes unexpectedly pregnant while travelling to a Zika infected country, it is quite predictable that she will undoubtedly be driven to take many blood tests and ultrasounds and experience a great deal of anxiety as she desperately hopes that her little one has dodged any Zika bullets.
Finally, a child born with microcephaly is not a trivial disorder. While about 15% of microcephaly cases turn out to be just babies with small heads and there is no discernable adverse effect on the infant, for the other 85%, these infants will experience a range of problems, all of which will have a profound negative impact on the quality of the child’s life throughout its entire life.
Given the observed impact Zika has already had on many LAC countries, there can be no doubt that Zika poses a clear and real Public Health threat for the populations who live in this region of the world. Well-thought-out, evidence-based protocols are needed and they need to be efficiently effected and implemented. While the Zika outbreak can defensibly be classified as an emergency, with prompt action this can be prevented from becoming a disaster. Yes, Zika is no Chikungunya, however, it still needs to be treated as though it could be.