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COVID-19 is a respiratory infection caused by the virus SARS-CoV-2. The virus spreads from person to person via respiratory droplets and small particles produced when an infected individual speaks or coughs. SARS-CoV-2 was first identified in China in 2019 and had not been isolated previously in humans or animals. Coronaviruses are very common and typically cause mild illness like common colds, but can be severe, like Middle East respiratory syndrome (MERS) and severe acute respiratory syndrome (SARS).



Transmission of COVID-19 occurs in three main ways (points 2 and 3 to a much lesser extent): 

  1. By inhaling aerosolised particles that contain the SARS-CoV-2 virus when in close proximity to an infected person.  
  1. Transfer of infected droplets or particles through the eyes, nose, or mouth. 
  1. By touching the eyes, nose or mouth with unwashed hands which have the virus particles on them.  

Being in a poorly ventilated space, in close proximity to someone with COVID-19, for a long period of time increases the risk of being infected. As new variants of the virus have emerged, they have become increasingly more infectious and transmissible. 

Health care workers exposed to patients with high viral loads are at increased risk of COVID-19 infection if not adequately protected by personal protective equipment and vaccinated.  


Individuals with COVID-19 can present with a wide range of symptoms, from relatively mild respiratory symptoms to severe illness. Symptoms may appear 2 – 14 days following exposure.  

For most individuals, early symptoms of COVID-19 appear like other respiratory viral infections – with a fever, dry cough, tiredness/lethargy and muscle aches. Other symptoms include a sore throat, chills, nasal congestion, headache, nausea and diarrhoea. An uncommon yet frequently encountered symptom involves the loss of taste and smell that occurs independently of nasal congestion.  

Common symptoms include:

  • Sore throat
  • Headache
  • Congestion
  • Fever or chills
  • Cough  
  • Shortness of breath or difficulty breathing
  • Fatigue
  • Muscle or body aches
  • Loss or change in taste or smell
  • Nausea or vomiting
  • Diarrhoea

Symptoms may change depending on the COVID-19 variant and can vary in severity depending on the vaccination status of the individual, their age and underlying health. In some individuals, COVID-19 can become much more severe, causing pneumonia and breathing difficulties. This can lead to acute respiratory and organ failure and wide-spread inflammation, which requires hospitalisation and intensive care.  


Treatments are available to reduce the risk of hospitalisation, severe illness and death, particularly in high-risk individuals. For treatment to be effective, it is advisable to commence treatment within days after symptoms first develop. Antiviral medications are available and funded to support certain older or high-risk individuals with COVID-19 infection.  

For more information on available treatment, click here.


Exposure risk 

Factors that increase or reduce the risk of COVID-19 transmission: 

  • Length of time – longer exposure to an infected individual increases the risk of COVID-19 transmission.  
  • Contact with symptomatic individuals – Coughing, singing and heavy breathing can increase the risk of transmission. Asymptomatic infected individuals have a lower risk of transmitting infection. 
  • Distance – Crowded settings with a high density of people can increase the likelihood of COVID-19 transmission.  
  • Masks – An N95 or high-quality mask reduces the risk of transmission. Risk is substantially decreased if the infected individual and susceptible person are both wearing masks.  
  • Ventilation – Exposure occurring outdoors can decrease the risk of transmission. Higher risk of transmission exists when indoors with poor ventilation.  

Risk of severe illness 

The risk of severe COVID-19 and death increases with age, chronic health conditions, such as diabetes, obesity and chronic respiratory disease, and with certain disabilities and in pregnant individuals. 

Factors that increase risk of severe COVID-19 illness: 

  • Age – Older adults are more likely to have severe COVID-19 infection, this risk increases exponentially for those aged above 50 years.  
  • Immunocompromise – Individuals with a weakened or compromised immune system are more likely to have severe COVID-19 infection.  
  • Comorbidity – Underlying health conditions, such as obesity, cardiac disease or respiratory disease may affect the risk of progressing to severe COVID-19 infection.  

For more information on factors that influence COVID-19 morbidity and mortality in Aotearoa, click here


Good hand-washing hygiene, social distancing, mask wearing and staying home when unwell help to reduce transmission. 

Immunisation remains the best form of protection against severe illness, hospitalisation and death. Immunisation with COVID-19 vaccines commenced in 2021. 

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