Novel surveillance methods for the control of Ebola virus disease Free

Abstract

The Ebola virus disease (EVD) outbreak in West Africa was unprecedented in size, leading to the death of over 11 000 individuals, with a further 17 000 infected,¹ and predictions of an additional avoidable 25 000 deaths per year from the loss of healthcare workers (HCWs) in the region.² The scale of the outbreak was largely attributable to uncontrolled transmission from infected contacts of cases who were not monitored due to limited access to screening and diagnosis, poor pre-existing surveillance mechanisms, including human resourcing and information technology,³ overstretched isolation facilities to limit transmission, and lack of treatment to reduce mortality.

Rapid and effective traditional surveillance systems, which include identification of possible cases by syndrome recognition with a mandatory reporting system, rapid laboratory confirmation of cases, community follow up, and regional/national standardised data aggregation and collection, have demonstrated their effectiveness in the eradication of smallpox and near eradication of polio.⁴ These approaches, used early in the EVD outbreak, were limited by lack of existing capacity and community mistrust and misconceptions, with subsequent lack of reporting of symptomatic individuals.⁵

Towards the end of the epidemic, novel public health approaches were also used, including large scale contact tracing with national coordination and ‘lockdown’ periods with door-to-door household reviews,⁶ rapid case identification and laboratory confirmation in both alive and dead, effective community engagement with messaging appropriate to specific communities, and appropriate infection prevention and control measures, which included safe burial. Implementation of this model of engagement in one Sierra Leone locality demonstrated a dramatic reduction in case numbers compared to elsewhere in the country.⁷

Innovative centralised command and control structures were implemented in Sierra Leone to allow for a coordinated approach to surveillance over the region, including monitoring of the geographic location of cases, real-time case-identification and reporting of suspect cases, detailed bed capacity within Ebola Holding Units (EHUs) and Ebola Treatment Centres (ETCs), and ambulance coordination for patient and body transfer.⁸ There is now a new, trained and experienced cadre of professionals, who came from a diverse background, including medical students and teachers, who can provide future resilience and preparedness, as well as a cohort of nursing staff who have significant experience in EVD recognition and management.⁹

Since surveillance capacity was limited in West Africa, alternatives to traditional methods were implemented, including community event-based surveillance (CEBS). In CEBS, selected community members were trained to identify suspicious events such as the presence of two or more deaths within a single household, or the death of a traveller, and were provided with a robust reporting system. CEBS was successfully implemented in June 2015 in Sierra Leone, and provided a useful adjuvant to countries that lack resources for dedicated disease surveillance at the end of an outbreak to allow for rapid detection of new cases.¹⁰ Using technology to improve surveillance, a novel open-source epidemiology platform (Epi Info Viral Hemorrhagic Fever [VHF] Application, v0.9.6.0., CDC, Atlanta, Georgia, USA) was deployed, originally in Guinea and subsequently in seven African countries, allowing for meaningful, comparable data to be collected across the region.¹¹ Further use of technology was trialled in later stages of the outbreak and included the use of GPS coordinates and direct data entry onto smartphones and tablets,¹² as well as the use of mobile phone text messages to report syndromic surveillance data.¹³ Given these successful trials, and the increasing proportion of mobile phone ownership and mobile network coverage in the countries affected by Ebola, we expect that smartphone technology will be used in the future for surveillance of infectious diseases in the region.

Laboratory confirmation is vital to surveillance efforts. Initial testing capacity in affected countries was very limited, with only one laboratory (at Kenema Government Hospital, Sierra Leone) able to test for EVD. By November 2014, pressures on international laboratory capacity testing led to significant delays in result availability: in one central EHU, patients died without a known EVD diagnosis nearly 2 days before a positive result was available, limiting vital contact tracing efforts given their potential high infectivity.¹⁴ Limited diagnostics for other pathogens that mimic EVD, such as malaria, dengue and typhoid, hampered control efforts.¹⁵ Upscaling laboratory capacity early in any future response will be vital to aid surveillance efforts and outbreak control.

Considerable effort has been afforded to determining a cluster of symptoms that allows for rapid and effective identification of patients with EVD, to curtail exposure to nosocomial infection for EVD-negative patients, and allow for effective use of limited beds for safe isolation of suspect cases. However, a universal set of symptoms, with adequate sensitivity and specificity for EVD, was not identified.^16,17 Therefore, the field deployment of highly sensitive rapid diagnostic tests, ideally with no cold chain storage requirements, could allow for rapid discharge of suspect patients with a negative result from EHUs, allowing the freeing-up of vital bed space and enabling routine care to continue.¹⁸ Towards the end of the outbreak, viral sequencing was linked to patient location, disease onset date, sample collection date and patient outcome,¹⁹ and pinpointed the single introduction from animal to human,²⁰ as well as demonstrating how infection was transmitted quickly across large distances and across borders.¹⁹ These important findings and capabilities will strengthen surveillance and response in the future.

Commitment to improved, integrated disease surveillance is key to rapid identification and containment of the re-emergence of EVD, and of other emerging infectious diseases in the region. Investment in robust laboratory infrastructure for all infectious disease aetiology is vital for future surveillance efforts beyond the three most affected countries in West Africa. For example, a review in northern Ghana highlighted that of ten patients flagged as EVD suspects during the outbreak, eight died with no cause of death identified, and significant gaps in HCW knowledge, health and surveillance infrastructure and outbreak preparedness were identified.²¹ We need to harness the lessons learned from West Africa: identification of novel diseases, timely dissemination of that information to potentially affected communities and health facilities alike, and the capacity to test for a variety of new and emerging pathogens, are the bedrock of disease surveillance. Novel mechanisms of disease control, including using new approaches to community engagement and information technology for surveillance, have the potential to augment these basic principles.

Authors’ contributions: CH, DY and CB wrote the paper and read and agreed the final version. CB is guarantor of the paper.

Funding: None.

Competing interests: None declared.

Ethical approval: Not required.

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