Early this week, the World Health Organization (WHO) confirmed 17 cases of vaccine-derived polio in children in eastern Syria, the second polio outbreak to impact the country since the beginning of the Syrian Civil War six years ago. Sixteen of the cases were found in the Mayadin district of the Deir al-Zor province, and the seventeenth case was found in Raqqa, the “self-proclaimed capital of the Islamic State” and an area that would be particularly dangerous for aid workers to reach. News of this growing polio outbreak comes just a week after the WHO confirmed 2 separate outbreaks (4 cases total) of vaccine-derived polio in the Democratic Republic of the Congo (DRC).

What’s happening in these countries begets important conversations about diverse health security issues—immediate and long term, specific and broad.

Both outbreaks represent disappointing setbacks to global polio eradication efforts. Polio is a disease that spreads from person to person, invading the brain and spinal cord and causing paralysis. As a result of strong and united public health efforts globally, the incidence of polio today is down 99.9% from what it was 30 years ago, when the disease affected more than 125 countries around the world and crippled more than 350,000 people per year, the majority of which were children under the age of 5. The case-fatality rate for polio in children is 2-5%, and this increases to 15-30% in adults; however, most individuals acquire immunity—either through immunization or community exposure to the vaccine strain of poliovirus—by the time they reach adulthood. If eradication efforts are successful, polio would become only the second human disease to be eradicated, after smallpox in 1980.  

According to the WHO, the polio outbreaks in both Syria and DRC were caused by circulating vaccine-derived poliovirus type 2, which can be secreted in the waste of children vaccinated with the oral polio vaccine utilized in some developing countries. The oral polio vaccine (OPV) uses an attenuated form of the virus that replicates in the intestine, and it is “10,000 times less able to enter the central nervous system than the wild virus.” In rare cases, however, when there is “insufficient coverage in a community the vaccine-virus may be able to circulate, mutate and, over the course of 12 to 18 months, reacquire neurovirulence.” Populations with “patchy vaccine coverage,” common in areas of active conflict, do not exhibit herd immunity, which provides ideal conditions for this type of transmission and, therefore, the incidence of vaccine-derived poliovirus outbreaks. In the past three years, Nigeria, Laos, Myanmar, and Ukraine have all reported vaccine-derived cases. Transmission of the wild-type virus still occurs in Afghanistan, Nigeria, and Pakistan.

                Given the generally poor public health and healthcare infrastructure in Syria and DRC, in combination with ongoing political and social instability, controlling these polio outbreaks will be difficult. According to the WHO, “weak health systems [that] struggle to vaccinate every child to ensure high enough protection within a community” pose one of the greatest challenges to eradicating polio. Additional logistical impediments, including “remote location, insecurity, and even conflict” further compound these challenges. In this case, health officials believe one of the infected children in the Syrian outbreak caught the disease in Raqqa. Because of the ongoing conflict, aid workers have been unable to reach populations in and around Raqqa to implement vaccination efforts.

Countries without sufficiently developed health sectors—such as Syria and DRC—will likely encounter even greater challenges when facing multiple outbreaks. Even a single outbreak can quickly overwhelm existing response capabilities, and additional concurrent or subsequent outbreaks can wreak havoc on health systems that are struggling to restore operational capacity. In this case, DRC very recently responded to an outbreak of Ebola virus disease, and the existing health sector resources likely have not yet fully recovered from the previous response, potentially impeding the response to the polio outbreaks.

Despite these particular challenges, DRC and Syria are not alone in their need to tackle emerging and reemerging infectious disease outbreaks while simultaneously addressing other acute and routine public health challenges. In thinking about how countries around the world can better prepare to respond to consecutive or concurrent public health threats, there may be lessons in how Nigeria fared during the West Africa Ebola epidemic (2013-2016). Many public health authorities feared that the introduction of Ebola to Nigeria, Africa’s most populous country, would lead to a seeding of the disease throughout the continent, but Nigeria’s response to Ebola was swift and effective. The outbreak was quickly contained due, in part, to capacities built as part of Nigeria’s polio eradication efforts. During the Ebola response, staff at Nigeria’s national Emergency Operations Center (EOC) were selected with particular focus on their involvement with Nigeria’s polio eradication campaign in 2012. Their prior experience with infectious disease response is believed to have contributed to Nigeria’s quick and effective response to Ebola.

It is clear that international support via training programs, funding, and other resources can help build and maintain public health and healthcare infrastructure in countries like DRC and Syria, increasing the likelihood that they will be resilient to future infectious disease threats. Programs like the US CDC’s Field Epidemiology Training Program support a broad range of outbreak surveillance and response capabilities. In Nigeria for example, the US CDC provided resources and training to help establish the Nigeria CDC in 2010. Other programs like President’s Emergency Plan for AIDS Relief (PEPFAR) or the President’s Malaria Initiative (PMI) target a single disease threat. Even those funding sources with narrow scopes can have far-reaching health sector impact, as the programs and capabilities that these investments help develop (eg, disease surveillance, laboratory capacity) can be applied to address a wider range of disease threats. In Nigeria, assistance from the United States includes support for the Nigeria Field Epidemiology Laboratory Training Program through US funding programs like PEPFAR, which provided critical laboratory capacity to support the Ebola response. The country’s success in containing the Ebola outbreak utilizing broad health sector capabilities as well as those developed specifically for other purposes illustrates that “learning to tackle one disease can pay off against another.”

Public health capabilities must be broad enough to tackle various types of disease events but also scalable to tackle multiple threats at once.  As was seen in Nigeria, the capabilities developed through support from programs like PEPFAR and polio eradication were successfully scaled and leveraged during the Ebola response. The situation in DRC and Syria illustrates the need for countries to build robust and scalable preparedness and response capacities, and for international investment to support these efforts, in order to successfully combat infectious disease events.