COVID 19

Epidemiology

The epidemiology of COVID-19 in NSW has continued to evolve since the first three cases were reported in NSW on 25 January 2020 in people who acquired their infection in China. The first locally acquired COVID-19 case in NSW was reported on 2 March 2020 and by mid-March case numbers had increased rapidly in overseas returned travellers and their contacts and within localised community outbreaks. In NSW, the number of reported daily cases peaked on 27 March 2020 at 213 cases. Public health action and the introduction of a range of stringent control measures, including the closure of international borders, 14-day mandatory quarantine for returned travellers and restrictions of movement within NSW lead to a decline in cases. Community transmission was interrupted by the end of May 2020. In early July seeding of SARS-CoV-2 into South Western Sydney from an outbreak in Melbourne led to a second wave of infection. Following intensive public health action community transmission was again interrupted by the end of November 2020. In December 2020 two new introductions of SARS-CoV-2 caused outbreaks in Sydney’s Northern Beaches and Berala in Sydney’s West. Community transmission was again interrupted by the end of January 2021. The delta outbreak across NSW began on 16 June 2021 in Sydney’s east, and spread from there to West and South Western Sydney. Clusters have developed throughout NSW.

Infectious agent:

SARS-CoV-2 is the infective agent that causes COVID-19. SARS-CoV-2 is a novel coronavirus that was first identified in humans in Wuhan, China, in December 2019. Like all viruses, SARS-CoV-2 has changed over time resulting in new variants. Detailed information about these variants is available here.

Transmission:

SARS-COV-2 can be transmitted through respiratory droplets, smaller particles (aerosols), direct physical contact with an infected individual, and indirectly through contaminated objects and surfaces.  (Department of Health 2021 p7 citing WHO. Transmission of SARS-CoV-2: implications for infection prevention precautions 2020 [updated 9 July 2020. Available from: https://www.who.int/news-room/commentaries/detail/transmission-of-sars-cov-2-implications-for-infection-prevention-precautions.)

Incubation period:

The majority of people become symptomatic 5 to 6 days after coming into contact with another infected person, with a range of 1 to 14 days  (Department of Health 2021 p8 citing
Quesada JA, López-Pineda A, Gil-Guillén VF, Arriero-Marín JM, Gutiérrez F, Carratala-Munuera C 2021; Elias C, Sekri A, Leblanc P, Cucherat M, Vanhems P. 2021; Daley C, Fydenkevez M, Ackerman-Morris S. 2020).

Infectious period:

Both pre-symptomatic and asymptomatic transmission can occur. Pre-symptomatic transmission can occur 1-3 days before symptom onset. Peak viral load in upper respiratory tract samples occurs most often around the time of symptom onset and declines after the first week following symptom onset.

Clinical presentation:

Patients with COVID-19 may present symptoms ranging from mild to severe.
The most common symptoms are fever, cough, dyspnoea, malaise, fatigue, loss of taste and/or smell, and sputum/respiratory secretions. Other symptoms include headache, sore throat, shortness of breath, myalgia, rhinorrhoea, chills, and vomiting. Atypical symptoms may include chest pain, diarrhoea, and conjunctivitis.
COVID-19 is generally a mild disease in children. Its severity, rate of hospitalisations and deaths increase with increasing age and with the prevalence of some comorbidities.

Vaccination:

COVID-19 vaccinations began in Australia on 22 February 2021. The first people to receive the COVID-19 vaccines were priority groups at a higher risk of COVID-19 infection, including quarantine and border workers, frontline healthcare workers, and aged and disability care residents and staff. People receiving vaccines are considered fully vaccinated two weeks after they complete the recommended course for that vaccine. All the vaccines being administered in Australia, and most from overseas, recommend a two-dose course.

References:

Agency for Clinical Innovation https://aci.health.nsw.gov.au/covid-19/critical-intelligence-unit accessed 26 October 2021

Department of Health Coronavirus Disease 2019 (COVID-19) (health.gov.au) version 5.1 accessed 25 October 2021

NSW Health https://www.health.nsw.gov.au/Infectious/covid-19/Documents/covid-19-surveillance-report-20211025.pdf accessed 25 October 2021