SPECTRUM Insights: Endemic Infections

One of SPECTRUM’s key themes is endemic infections. We’ve heard all about epidemics and pandemics over the past year, but what are endemic infections?

As the end of 2020 draws nearer, the whole world is wondering when the COVID-19 pandemic will end. Vaccine rollouts will soon be underway in several countries, and other treatments are being considered. Hard lockdowns have eased in Australia, while other countries hold onto the hope that mass administration of vaccines in 2021 will see case numbers fall and life return to pre-COVID normalcy. For many, we are on the precipice of something historic – a victory over the destructive and formidable enemy that is COVID-19. The end of a pandemic.

While people bask in the hope that the new year brings, it would be remiss of us to believe a pandemic could come and go so easily. For those expecting COVID-19 to disappear, we have some news: COVID-19 may never go away. Despite everyone’s best efforts, and all the money and time that has been dedicated to stopping this disease from spreading, the most likely next phase is that COVID-19, like many other infectious diseases, will become endemic.

Only time will tell how much its spread and impact can be reduced by immunity resulting from past infection and vaccination, but SARS-CoV-2 will likely join the collection of coronaviruses that circulate in human populations over the years to come.

While COVID-19 has everyone’s attention, other endemic diseases have persisted for years with little change despite targeted intervention strategies and investment in the eradication of endemic infections.

What are endemic infections?

Endemic diseases are consistently present within a population and are constantly circulating, and even with treatments and interventions like vaccines, endemic infections continue to spread. The prevalence, or the number of people infected with a certain illness at any one time, remains relatively constant. The rate of infection can become stable and predictable, with some fluctuation. Decisions to be made for their control are important, but not necessarily urgent (1). There is time to gather needed evidence on burden and drivers in the local setting, develop models and collect additional data as required to contextualise relevant experience of interventions applied elsewhere, and consider likely outcomes of alternative prevention and control strategies.

While some endemic infections are present and are actively spread worldwide, such as HIV, Hepatitis B and some sexually transmitted diseases, many endemic diseases are present within a specific geographical area, including malaria, polio and scabies.

What is the difference between endemic infections and epidemics?

Endemic diseases are constantly circulating in a specific population or geographic area, often at a predictable rate. An epidemic is a disease outbreak, when a disease spreads rapidly in a short period of time within a specific population. This can be widespread and needs to be addressed with urgency to prevent the rapid spread of disease.

A pandemic is an epidemic that has become widespread, with cases detected worldwide.

Why is it important to treat endemic infections?

Although epidemics and pandemics attract a lot of attention, the disease burden of endemic infections is substantial.  Endemic infections can prevent the economic and social advancement of populations and can perpetuate social and financial disadvantages including poverty and poor quality of life. Endemic infections can affect different populations, but people living in low- and middle-income countries are disproportionately affected. Social determinants of health play a major role in the spread of endemic infections, resulting in the need for a concerted and holistic approach to treating and preventing these diseases.   

How can endemic infections be eradicated?

Realistically, some endemic infections may never be eradicated, but if we have a good understanding of the disease, we can use the right methods and tools to reduce disease severity and disease burden, and to mitigate the risk of further transmission. Although eradication is the ideal goal, there are many challenges that prevent this from happening for some infectious diseases.

Endemic infections can be addressed using a variety of strategies, including behaviour changes, improved health literacy, improved diagnostics, vaccines, and a combination of pharmaceutical and non-pharmaceutical interventions.

What endemic diseases will SPECTRUM focus on?

One endemic infection SPECTRUM will focus on eliminating is scabies. Scabies is an intensely itchy skin condition caused by infestation with the mite Sarcoptes scabiei, estimated by the World Health Organisation (WHO) to affect 200 million people globally at any one time. While non-fatal, it has a substantial impact on quality of life. Scabies is endemic, with prevalence as high as 35% in children and 25% in adults, in many remote northern Australian communities (2). It substantially increases the risk of other secondary skin infections, including Group A streptococcus, with risks of invasive infection and long-term sequelae including rheumatic heart disease (2). Scabies is a stubborn problem driven by close mixing in crowded household environments, particularly in tropical regions and settings of poverty (3). Existing investments in intervention strategies have not changed this burden in 25 years (3).

How is SPECTRUM contributing towards the prevention and control of endemic infections?

SPECTRUM will collaborate with the International Alliance for the Control of Scabies, ACE-NTD (NHMRC Centre of Research Excellence: The Australian Centre for the Control and Elimination of Neglected Tropical Diseases), HOT NORTH (NHMRC: Improving Health Outcomes in the Tropical North) and NGO One Disease to devise definitive strategies for national and global elimination of scabies. SPECTRUM and its collaborators are using mathematical models to analyse different interventions, including mass drug administration and treatment approaches. The model findings will be communicated to the International Alliance for the Control of Scabies (IACS) and the WHO Strategic and Technical Advisory Group for NTDs, to help define the next strategies and goals for the elimination and control of scabies.

 

Drawing on the observations made in other scabies-focused projects and with expertise from community-based researchers SPECTRUM will translate model outcomes into policy and practice by defining acceptable interventions to be trialled in partnership with communities, providing needed evidence of field effectiveness to inform future clinical and public health practice recommendations for sustainable control of scabies and associated skin infections.

 

(Written by Laura Bannerman with technical expertise provided by Professor Jodie McVernon)

 

  1. Sands P, Mundaca-Shah C, Dzau V. The neglected dimension of global security - a framework for countering infectious-disease crises. New Engl J Med. 2016;374(13):1281-7.
  1. Aung PTZ, Cuningham W, Hwang K, Andrews RM, Carapetis JR, Kearns T, et al. Scabies and risk of skin sores in remote Australian Aboriginal communities: A self-controlled case series study. PLoS Negl Trop Dis. 2018;12(7):e0006668.
  1. Karimkhani C, Colombara DV, Drucker AM, Norton SA, Hay R, Engelman D, et al. The global burden of scabies: a cross-sectional analysis from the Global Burden of Disease Study 2015. Lancet Infect Dis. 2017;17(12):1247-54.
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