Containing infectious diseases
History has shown that high consequence infectious diseases (HCIDs) can have a devastating impact on society if not controlled. We look at the key features of HCIDs, their consequences for health clinicians and the importance of biocontainment.
For thousands of years, humans have struggled to improve their health and wellbeing in a vastly complicated and ever changing environment. History is peppered with examples of waves of poor health, disease and infection. Some communicable or infectious diseases, such as tuberculosis and influenza, are particularly challenging and have shaped the evolution of societies and cultures.
There are some infectious diseases that are particularly significant when it comes to their impact on societies and the environment. High consequence infectious diseases (HCIDs) are those that have one or more of the following overall features:
- the potential to cause epidemics or pandemics;
- infect or affect many people;
- spread rapidly in a short time;
- infection results in high cost to society, such as loss of worker productivity or interruption to society infrastructure and functioning; and
- that result in high cost to the healthcare system.1
How HCIDs spread
HCIDs are spread by different modes of transmission. Marburg virus haemorrhagic fever, Crimean-Congo haemorrhagic fever, Lassa fever and Ebola virus disease (EVD) are spread by contact. Other such diseases, including Middle East respiratory syndrome coronavirus (MERS-CoV), Monkeypox, Avian influenza, pneumonic plague and other respiratory pathogens are spread via airborne transmission. In some instances, they are emerging infectious diseases, that is, diseases that are either pre-existing or new in humans.
Emerging and HCIDs are often zoonotic, with the index human case being infected by an animal. For example, viral haemorrhagic fevers are HCIDs caused by over 30 viruses endemic to Africa, Eastern Europe, Asia and the Middle East, with reservoirs including fruit bats, ticks and rodents.3
Diagnosing viral haemorrhagic fever can be difficult in the early stages of infection due to non-specific symptoms of fever, weakness, myalgia and headache occurring. However, key to this is establishing a rigorous case definition, including assessing the travel history and individual behaviours in an endemic area. For example, EVD can present with clinical symptoms suggestive of typhoid fever, meningitis or malaria, all of which should be ruled out during the assessment.5
HCID risk to health personnel
HCIDs present a serious risk to public health and specifically, healthcare personnel, with infected cases often requiring a high level of care, such as an intensive care unit. Controlling the spread of infection and managing the resultant cases requires a national and international coordinated response, including rapidly initiating public health prevention and control strategies specific to the mode of transmission. The need for this degree of involvement was highlighted by the unprecedented scale of the outbreak of EVD in West Africa in 2014–2016.
While there have been numerous outbreaks of EVD since its discovery in 1976, this outbreak in West Africa was the first time a highly pathogenic virus had spread from remote areas to an international setting. The strain of EVD was highly pathogenic with over 28,600 infected cases and 11,308 deaths reported in Sierra Leone, Liberia and Guinea alone, with case fatality rates of 28%, 45% and 67%, respectively.5
Notably, medical evacuations exported the virus to the United States (US) and Europe for the first time, but with a lower-case fatality rate of 20%.3 Between August 2014 and December 2015, 27 patients with EVD were managed in 15 hospitals in nine countries across the US and Europe.
In West Africa, healthcare personnel had a higher rate of infection with EVD compared to the general population. In Sierra Leone, Liberia and Guinea, healthcare personnel comprised 815 cases, made up of 50% nurses; 12% doctors and medical students; and laboratory workers, janitors and maintenance staff 7% each, respectively. Of healthcare personnel with final outcomes recorded, over two-thirds died (418/635), disproportionately higher rates compared with the general adult population in those countries.7 Multiple possible risk factors for healthcare personnel infection have been identified, most highlighting deficiencies in infection prevention and control policies, procedures and practices, including problems with personal protective equipment and lack of engineering and environmental control.7
Biocontainment: essential for HCIDs
The strategy for dealing with EVD in West Africa was focused on two key principles:
(i) biocontainment or isolating cases to prevent ongoing community transmission, using rapidly constructed and demountable Ebola Treatment Centres; and
(ii) the provision of supportive care by local and international healthcare personnel to manage the clinical manifestations of disease and improve patient outcomes.8
Purpose-built biocontainment facilities originated in 1969 when Lassa Fever was discovered. They were created to mitigate the risk of laboratory workers, and subsequently the community, from being exposed to lethal infections. Beyond this were concerns about possible bioterrorism events or a laboratory accident with a highly infectious and pathogenic agent such as smallpox.9
Specialist biocontainment units for HICDs are located around the world. Biocontainment units at the Nebraska Medical Centre and Emory University Hospital in the US, and the Royal Free Hospital in the UK, are amongst the most experienced units in the Western World in dealing with HCIDs, in particular EVD. Together, these facilities managed 10 (37%) of the 27 cases of EVD in the US/Europe during the recent EVD outbreak and are on a 24-hour, 365-day alert to receive a patient with a HCID as part of a coordinated national response.6 There are other well-established units globally, in particular in Norway, Germany and Singapore.
Managing EVD and HCIDs in the US and beyond yielded many lessons for outbreak response teams, and these have gone on to inform policy and practices around the world. For example, it became clear that patients with HCIDs have a much higher acuity and a high level of critical care not typically seen in most infectious diseases. Moreover, their acuity varied from healthy to critically ill, to convalescence, and at times recurrence and even secondary infection.
As such, HCID patients required biocontainment for much longer than classically anticipated, and importantly, many current biocontainment units were not designed for all events and potential care required.10 These findings have been incorporated into engineering designs of new biocontainment facilities, such as a through-wall autoclave to enable waste to be disinfected at the point of care. Newer models incorporated capacity for one-way flow and laboratory testing facilities to limit cross-contamination of waste within the unit.10
Australia is equipped with designated facilities to manage viral haemorrhagic fevers and other HCIDs across its states and territories. In NSW, Westmead Hospital in Sydney’s west is the designated viral haemorrhagic fever hospital. Here, a purpose-built biocontainment facility is planned — the New South Wales Biocontainment Unit (NBU) — for case management and high-level isolation, to deliver high-quality health care and to protect the community from HCIDs for decades to come.
- Centers for Disease Control and Prevention. Emerging Infectious Diseases: High-consequence pathogens. 2018. Accessed February 4, 2019.
- McCloskey B, Dar O, Zumla A, Heymann DL. Emerging infectious diseases and pandemic potential: status quo and reducing risk of global spread. Lancet Infect Dis. 2014;14(10):1001-1010.
- Leligdowicz A, Fischer WA, 2nd, Uyeki TM, et al. Ebola virus disease and critical illness. Critical Care. 2016;20(1):217.
- Centers for Disease Control and Prevention. Viral Hemorrhagic Fevers: Filoviridae. 2014; https://www.cdc.gov/vhf/virus-families/filoviridae.html. Accessed 09 May, 2018.
- World Health Organization. Ebola virus disease: Fact sheet. 2018; http://www.who.int/en/news-room/fact-sheets/detail/ebola-virus-disease. Accessed 21 February, 2019.
- Uyeki TM, Mehta AK, Davey RT, Jr., et al. Clinical management of Ebola Virus Disease in the United States and Europe. N Engl J Med. 2016;374(7):636-64
- World Health Organization. Health worker Ebola infections in Guinea, Liberia and Sierra Leone. 2015; 21 May 2015:https://www.who.int/csr/resources/publications/ebola/health-worker-infections/en/. Accessed 21 February, 2019.
- Chowell G, Viboud C. Controlling Ebola: key role of Ebola treatment centres. Lancet Infectious Diseases. 2015;15(2):139-141.
- Cieslak T, Herstein J, Kortepeter M. Communicable Diseases and Emerging Pathogens: The Past, Present and future of High Level Containment Care. In: Hewlett A, Murthy A, eds. Bioemergency Planning: A Guide to healthcare facilities. Switzerland: Springer International Publishing; 2018.
- Crane J, McCullough C, Inc. H. High-consequence infectious disease: 10 principles for patient safety. 2017. https://www.hdrinc.com/insights/high-consequence-infectious-disease-principles-models-patient-safety#. Accessed 23 April 2017.
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