COVID-19 and breaking the chain of infection

By Professor Ramon Z Shaban*, Dr Cristina Sotomayor-Castillo**, Kaitlyn H Radford^, Jeremy Malik^, Samantha Bell^^
Tuesday, 07 April, 2020

COVID-19 and breaking the chain of infection

Global news and social media platforms are flooded with information about the outbreak of the 2019 coronavirus disease known as COVID-19 caused by the novel agent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

Since first being reported to the World Health Organization (WHO) on 31 December 2019,1, 2 COVID-19 has rapidly spread from China to every continent in the world except Antarctica. WHO declared the situation a global health emergency of international concern on 30 January 2020, then a global pandemic on 11 March 2020. In the space of three months the virus spread to more than 170 countries, with more than 330,000 cases and 14,000 deaths. It is widely reported to be an unprecedented global pandemic like nothing we have seen in more than a century, with fears of it eclipsing the 2009 swine flu pandemic and overtures of the severity of the great 1918 Spanish Flu.

At the time of writing it is still very early on in the timeline of the outbreak — literally less than three months — and there are many things we don’t know about this virus and disease. As a novel or ‘new’ virus, there have been, are, and will be very many questions about it. One key question that is common to all outbreak investigations is what the source of the infection was and how did it find its way into human populations? We understand it to be a zoonosis — an infection that animals are the host of, and which humans are accidental or incidental hosts. There are countless other questions that health professionals, scientists and the whole world are asking, and an enormous global thirst for information.

Despite these unknowns, there is much that we do know about this infection and disease — health professionals and scientists have learned a great deal in the space of weeks and months since this all started in late December 2019.

We know that this infection is caused by a virus, in particular a coronavirus. Coronaviruses are not new. They are a family of viruses, with which humans have considerable experience. The common cold is a coronavirus — as is the severe acute respiratory syndrome coronavirus 1 (SARS-CoV-1) — responsible for an outbreak occurring in 2003 — and also the Middle East respiratory syndrome coronavirus (MERS-CoV), which saw another outbreak first reported in 2012.

SARS-CoV-1 and MERS-CoV — both contagious, sometimes fatal respiratory illnesses — have generally similar clinical characteristics to COVID-19.

Clinically, COVID-19 presents like many other respiratory illnesses, with classic symptoms including fever, sore throat, cough and difficulty breathing.3 We understand the incubation period of COVID-19 to be between one and 14 days, with a mean incubation period varying between five and seven days.

Although SARS-CoV-1 and MERS-CoV have generally similar clinical characteristics to COVID-19, the death rate is somewhat different. SARS-CoV-1 had a case fatality rate of 11%; MERS-CoV approximately 35%. SARS-CoV 1 was contained in 2004 and extinguished shortly thereafter; but MERS-CoV cases have continued in small numbers since 2012, with 2494 cases and 858 deaths across 27 countries.

We know there is no definitive treatment for the infection or disease, with no antibiotic or specific antiviral agent available. Moreover, there is no vaccine, and little prospect, if any, of one being available in the short to medium term.

We also, rather critically, understand that the mode of transmission of the infection is via contact and droplet transmission. In basic terms this is very important, because it goes directly to our efforts to interrupt transmission and break the chain of infection. Understanding how the infection is spread is fundamental to our efforts to prevent and contain its spread, especially when there is no definitive treatment available.

In terms of infection prevention and control strategies, WHO recommends employing basic hygiene principles that are known to reduce the risk of transmission of acute respiratory infections4 via standard and transmission-based precautions. Standard precautions include hand hygiene (consistent with the 5 Moments for Hand Hygiene); use of personal protective equipment (PPE); safe use and disposal of sharps; routine environment cleaning; reprocessing of re-usable medical equipment and instruments; respiratory hygiene and cough etiquette; aseptic technique; waste management and appropriate handling of linen.

Contact precautions include use of appropriate PPE, including gloves, aprons or gowns, eyewear, face shields and face masks. For droplet precautions, a surgical mask is indicated. Droplet precautions include the use of surgical masks for healthcare workers and coughing patients as well as maintaining proximity of more than one metre when possible.

Airborne precautions include the use of P2 or N95 respirators for healthcare workers, use of surgical masks for coughing patients and the use of negative pressure rooms, where possible.5 Other elements include dedicated equipment; allocation of single rooms or cohorting of patients; enhanced cleaning and disinfecting of the patient environment; and restricted transfer of patients within and between facilities.

Routine sanitisation of hands and high-touch surfaces are considered successful and cost-effective measures for limiting the spread of disease. Recommendations against the COVID-19 outbreak indicate that frequent handwashing should be exercised, especially after direct contact with ill people or their environment. Individuals with symptoms of acute respiratory infection should practise cough etiquette by maintaining distance and covering coughs and sneezes with disposable tissues or coughing or sneezing into their elbow. Where possible, close contact with people suffering from acute respiratory infections should be avoided.6

The novel and dynamic nature of this outbreak means that things happen and change quickly. It is vital that every individual, from healthcare workers to community members, refer to official, reliable, trusted sources of advice. Importantly, the systematic and sustained application of standard and transmission-based precautions, which we know are effective, is what will afford us the greatest opportunity to see our way through this outbreak safely and effectively.

*Professor Ramon Shaban is the Clinical Chair and Professor of Infection Prevention and Disease Control within the Marie Bashir Institute for Infectious Diseases and Biosecurity and Susan Wakil School of Nursing and Midwifery at the University of Sydney and the Division of Infectious Diseases and Sexual Health at Westmead Hospital and Western Sydney Local Health District.
**Dr Cristina Sotomayor-Castillo is a Research Fellow to Professor Ramon Shaban at the Susan Wakil School of Nursing and Midwifery and Marie Bashir Institute for Infectious Diseases and Biosecurity, University of Sydney.
Kaitlyn Radford and Jeremy Malik are research affiliates at the Susan Wakil School of Nursing and Midwifery and Marie Bashir Institute for Infectious Diseases and Biosecurity, The University of Sydney.
^^Samantha Bell is a postgraduate student of the School of Public Health within the Faculty of Medicine, University of Sydney.

  1. Novel Coronavirus (2019-nCoV) SITUATION REPORT - 1 [press release]. World Health Organization, 2020.
  2. Hui DS, E IA, Madani TA, Ntoumi F, Kock R, Dar O, et al. The continuing 2019-nCoV epidemic threat of novel coronaviruses to global health - The latest 2019 novel coronavirus outbreak in Wuhan, China. Int J Infect Dis. 2020;91:264-6.
  3. Chen N, Zhou M, Dong X, Qu J, Gong F, Han Y, et al. Epidemiological and clinical characteristics of 99 cases of 2019 novel coronavirus pneumonia in Wuhan, China: a descriptive study. The Lancet. 2020.
  4. World Health Organization. Global Surveillance for human infection with novel coronavirus (2019-nCoV). World Health Organization, ; 2020.
  5. Council NHaMR. Australian Guidelines for the Prevention and Control of Infection in Healthcare (2019). 2019.
  6. Nicolaides C, Avraam D, Cueto-Felgueroso L, Gonzalez MC, Juanes R. Hand-hygiene mitigation strategies against global disease spreading through the air transportation network. bioRxiv. 2019:530618.

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