Zika Virus
February 2, 2016
On February 1, Margaret Chan, the Director General of the World Health Organization (WHO), acting on the recommendations of 18 infectious disease experts, stated:
"I am now declaring that the recent cluster of microcephaly cases and other neurological disorders reported in Brazil, following a similar cluster in French Polynesia in 2014, constitutes a Public Health Emergency of International Concern.”[1]
Chan’s decision is only the fourth PHEIC since revised International Health Regulations came into force in 2007. It follows the Director General’s declarations on swine flu (2009), polio (May 2015), and Ebola (August 2015).
The declaration is a welcome and timely step, in my view, given the scale of the microcephaly cases, the explosive spread of Zika across the region, and the complex, murky science. There is a suspected but not yet scientifically proven link between Zika and microcephaly and, in adults, between Zika and Guillian-Barré Syndrome, a neurological condition that sometimes leads to temporary paralysis.
No doubt the decision to declare an emergency was influenced by the fresh memory of WHO’s exceptionally poor performance at the outset of the Ebola outbreak in West Africa in early 2014. Arguably, were it not for the heavy shadow of Ebola and the felt need at the upper reaches of WHO to rebuild the agency’s frayed reputation and minimize the risk of yet another round of harsh criticism for WHO delays, the decision might have been otherwise. The WHO Emergency Committee might very well have chosen to issue detailed advisories and meet quarterly, as it does for MERS, stopping short of an actual declaration of an emergency. Reportedly, the expert committee debated this question extensively, over several hours, before concluding an emergency declaration was indeed warranted.
Be that as it may, the DG ultimately did issue the emergency declaration which now invests WHO with enhanced authority to focus high-level attention and mobilize resources internationally. WHO is explicitly expected to lead international coordination to accelerate scientific research, monitor and track both microcephaly and Zika, and press for expansion of mosquito controls and other protective measures, especially to protect pregnant women. Henceforth, WHO’s performance in this instance will be judged according to how well it actually does in delivering results in these critical areas. It remains to be seen whether WHO is capable of sustained high-level leadership in the final year of Margaret Chan’s tenure, and whether this phase does indeed unveil a revitalized and improved WHO. The hope is that much concrete progress is seen in 2016.
Infants born with microcephaly have undersized heads and the majority suffer brain damage. Over 4,100 cases have been reported in northeast Brazil since late last year.
These cases have arisen in the same period that the Zika virus, carried by the Aedes aegypti mosquito (the same mosquito that carries dengue and chikungunya) entered the Americas in 2014 and spread explosively across the hemisphere among populations with no immunity.
Upwards of 1.5 million persons have become infected, while the WHO projects that number will reach 4 million in 2016. At present, Zika has spread to 28 countries in the hemisphere. As of this writing, 31 cases have been reported in the United States by returning travelers; 20 cases have been reported in Puerto Rico and the US Virgin Islands.
The majority of persons infected with Zika do not become symptomatic, and those who do typically only experience mild symptoms (rash, fever, joint pain.)
For reasons not fully understood, the Zika virus appears to pose a special threat to pregnant women. Whether, how and why the Zika virus is causally linked to birth defects among infants, and whether it involves co-infection with other viruses or a new mutation in the Zika virus, are today the most pressing scientific issues on the table, alongside understanding the association between Zika and Guillian Barre Syndrome, and the urgent need to accelerate the development of a rapid test, vaccine and treatments. These are the central challenges before the WHO and its allies: to get the science right, quickly, by bringing coherence and a common surveillance framework to now disparate research and data collection efforts.
President Obama convened his health and national security teams on January 26 and supported a response that emphasizes accelerated research and awareness by both the public and health care community. NIAID has prioritized funding into Zika virus research and product development, urging scientists working on related viruses to shift efforts to Zika. NIAID researchers have begun developing vaccine candidates and are working with CDC to develop diagnostic tests. CDC experts are tracking Zika in the US as a newly notifiable condition for state health departments, and providing assistance to public health officials in affected countries.
In the summer of 2016, it is expected that there will be transmission of Zika on American soil. According to CDC Director Dr. Thomas Frieden, the risk of a serious outbreak in the United States is low, owing to established capacities to control mosquito populations and widely available air conditioning.
“For a disease such as Zika to spread widely, two things are necessary. The first is the specific mosquito species that spreads the virus. The second is the conditions in communities; places that are crowded and don't have air conditioning enable viruses such as Zika to spread.
So we do expect, unfortunately, that Puerto Rico and the U.S. Virgin Islands could have many infections with the Zika virus, and we will certainly see U.S. travelers returning with Zika infections, just as we saw travelers returning with dengue and chikungunya infections. We could see isolated cases and small clusters of infections in other parts of the country where the mosquito is present. But from the information we know now, widespread transmission in the contiguous United States appears to be unlikely.”[2]
The top concern among U.S. policymakers remains the protection of pregnant women or women likely to become pregnant: on January 15, CDC issued a warning that pregnant women should not travel to Zika-affected areas.
No such travel warning is contained in the WHO emergency declaration . In her statement, Margaret Chan explained: “The Committee found no public health justification for restrictions on travel or trade to prevent the spread of Zika virus. At present, the most important protective measures are the control of mosquito populations and the prevention of mosquito bites in at-risk individuals, especially pregnant women.”
In all likelihood, that omission reflects Brazil’s influence and its determination to give high priority to protecting the Olympics Brazil will be hosting in August. Presumably also, that omission reflects a broader concern across the region that any emergency declaration not impose undue economic costs through disrupted trade, investment, and travel, including in the tourist sector, unless there is a powerful and indisputable public health case.
Whatever the reasons for not advising pregnant women to avoid travel to Zika-affected areas, there is now a conspicuous gap between US and WHO policy approaches. And WHO carries an implicit vulnerability: should there be a proliferation of travel-derived microcephaly cases among newborns, WHO could face a storm of criticism. That might be ameliorated to the degree that Brazil and other countries issue their own national travel warnings to pregnant women.
[1] WHO Director-General summarizes the outcome of the Emergency Committee regarding clusters of microcephaly and Guillain-Barre syndrome. 1 February 2016
[2] Dr. Tom Frieden, Special to CNN, February 1, 2016.
