Key Interventions in a Disease Outbreak Response

Once a disease outbreak is detected and a response triggered, the challenge of prioritising and implementing effective interventions begins. In this step Antonio Isidro Carrion Martin, Anna Kuehne and Rosamund Southgate (Médecins Sans Frontières) outline the key principles and components involved in launching an effective response.

The sister of a boy diagnosed with diphtheria holds vaccine issued by a community nurse making a home visit to prevent onward transmission, Cox’s Bazar, Bangladesh

© Louis Leeson/LSHTM

What are the critical interventions in an outbreak response?

The first key intervention, once an outbreak has been declared, is to establish an effective outbreak control or coordination team. The role of this team is to ensure that all the activities needed in the response are established – these activities are usually grouped into outbreak response “pillars” (Figure 1), which we explored last week in the step What is an outbreak response? The outbreak control team is also responsible for the coordination, communication and interaction among different actors, and between different pillars, as well as ensuring that resources are allocated and prioritised where they are most needed.

Figure 1: Outbreak Response Pillars

The pillars help to group the different responders involved in outbreak response around thematic areas. Multidisciplinary teams are involved in outbreak response, and we will revisit later this week the specific roles in interventions of clinicians, epidemiologists, microbiologists, social scientists, IPC specialists, WASH specialists and logistics and security specialists.

How do the critical elements of interventions change by disease?

The pillars of response will vary depending on the context and on the outbreak disease. For example, an outbreak of malaria will not have a vaccination component (there is no effective vaccine) or a contact tracing component. In the case of a malaria outbreak the expert advice of an entomologist or vector control specialist is crucial. In contrast, an outbreak of diphtheria would require a strong contact tracing component within the surveillance pillar and a vaccination component.

It is key to avoid a “siloed” approach with all interdisciplinary pillars working in continuous communication and collaboration. For example, if social scientists work on better understanding the communities affected, the epidemiologists benefit from the information to better understand the transmission dynamics. In the Ebola outbreak in West Africa, understanding the socio-cultural context and community perceptions helped to improve community engagement and prevent Ebola virus transmission.

A woman suspected of contracting Lassa fever awaits laboratory results in isolation, Abakaliki, Nigeria

© Louis Leeson/LSHTM

How are interventions coordinated and prioritised?

The pillar system in outbreak response usually includes the following components:

• Case management activities are key to reduce morbidity and mortality and to restore dignity; treat or support those who are unwell with the outbreak disease; and often, reducing transmission by isolating infected people from the rest of the population. The main components are: active case search; decentralised care; referral system; triage; care staff training and supervision; supply chain; adequate treatment protocols; and isolation. Laboratory, WASH and IPC teams play a crucial role in triage of patients, and the establishment of adequate isolation and IPC measures. In an outbreak of cholera, for example, decentralised care with oral rehydration points aim to reduce morbidity and mortality by preventing severe cases. Additionally, good triage in a cholera treatment centre is crucial to quickly and accurately establish the treatment category required for each patient.
• Infection prevention and control activities are crucial to stop the outbreak and key components include: infection prevention and control; vaccination; and water, sanitation and hygiene interventions. In the event of an Ebola outbreak, prevention and control activities include safe burial practices.
• Social mobilisation and community engagement are important in all activities, for example, health promotion is crucial for prevention and control activities at the community level. Community compliance with the proposed measures is often a challenge, understanding the affected communities and involving them in response activities critical to a successful response. For example, in any vaccination campaign, the social scientist team should establish the most socio-culturally appropriate communication and social mobilization strategy for the setting to ensure high vaccination uptake.
• Surveillance and disease intelligence activities are essential to understand the transmission dynamics and epidemiology of the outbreak to determine the most appropriate prevention and control measures. An outbreak investigation is crucial to inform interventions and the key components are:
  –Develop a case definition. Laboratory confirmation for all cases may be a challenge for many diseases in these contexts. This will vary depending on the disease, for example, in an Ebola outbreak all possible efforts are made to test all suspected cases. In contrast, once a measles outbreak is declared testing suspected cases is not a priority, as often, there is no local capacity to test.
  –Find cases to understand the spread and epidemiology of the outbreak and increase access to early treatment.
  –Describe the outbreak in terms of person, place and time and generate a hypothesis about transmission dynamics and risk factors to inform prevention and control measures. For example, in an outbreak of cholera, information about the origin of patients and location of water sources may be enough to inform the WASH team outbreak control activities.
  –Document and evaluate the intervention to inform and strengthen future outbreak responses. There is not always the capacity to evaluate the intervention, however a report describing the outbreak and the response activities should always be written as it could be very helpful in future responses in the same or similar areas. For example, the documentation of a precise cumulative attack rate, time to peak and overall duration will help forecast how future outbreaks will evolve.

An ongoing surveillance system contributes data to describe the outbreak and inform the response. It is important to establish an effective data collection system, with a clear data flow and a well trained data collection/surveillance team. Simplicity in data collection will be key during an outbreak where the whole health system may be overwhelmed and resources may be scarce. Therefore the type and amount of information collected should be prioritised and kept to a minimum. For example, in a large meningitis outbreak, there is unlikely to be sufficient capacity available to collect data on household associated risk factors for every patient, and therefore this is not a priority. It will be more effective to focus on high data quality for core variables (e.g. origin, age, sex, outcome) that will inform the current response.

In some outbreaks, like viral haemorrhagic fevers, the alert system and contact tracing will be one of the most important activities to stop the outbreak by identifying cases as soon as they develop symptoms. Together with active case search, infected people can be treated and isolated to reduce morbidity, mortality and avoid further transmission.

A close monitoring of the outbreak will also be essential to forecast resources needed for the activities. In this regard it is important to have a precise population estimate to establish key epidemiological indicators (e.g. attack rates, mortality rates) that will help inform resource allocation (e.g. number of beds needed in health facilities). In practice, these population denominators are often difficult to obtain in these contexts.

• The logistics pillar will ensure that the “outbreak response machine” works smoothly. This team will assure adequate funds and its administration, so the supplies, transport and human resources can be put in place in a rapid and effective manner. In high security or unstable contexts, such as conflict-affected settings, logisticians will be responsible for security assessments, monitoring of teams and risk mitigation.

In conclusion, the key interventions of an outbreak response will vary depending on the setting or disease. Having the right expertise and resources, the appropriate coordination of different activities and the involvement of all the main partners, including the affected community, will be necessary in all types of outbreaks.