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COVID-19 (coronavirus disease 2019) is a respiratory viral infection caused by SARS-CoV-2 virus. From late 2019, this disease rapidly spread resulting in a pandemic. Early symptoms of COVID-19 include a dry cough, sore throat, fever, loss of taste and smell, tiredness, gastrointestinal symptoms, such as diarrhoea and pain, and muscle aches. In some people, particularly in older people and those with chronic health issues, it develops into pneumonia and widespread inflammation requiring hospitalisation and ventilation support in intensive care.


COVID-19 is a respiratory infection caused by a new type of coronavirus called SARS-CoV-2. It initially affects your lungs and airways. This new virus that was first identified in China in 2019 and had not previously been seen in humans or animals. Coronaviruses are known to cause mild illnesses like common colds but also severe diseases like severe acute respiratory syndrome (SARS) and Middle-East respiratory syndrome (MERS).

How you get it

SARS-CoV-2 virus is primarily spread person to person by aerosols of droplets from airways, such as through coughing and sneezing. Being in a poorly ventilated space, in close proximity of someone who is infected and being exposed for several minutes increases the risk of being infected. Singing and loud conversation can increase spread from infected people. There is also some limited risk of infection after touching contaminated surfaces. More infectious variants of the virus have increased infectiousness and are more likely to be airborn that earlier variants.

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


The early symptoms of COVID-19 appear like other respiratory viral infections, with fever, dry cough, tiredness and muscle aches. Other symptoms include a sore throat, nasal congestion, headache and diarrhoea. An unusual but common symptom is the loss of taste and smell that is not associated with nasal congestion. For some people, this disease becomes much more severe, causing pneumonia and breathing difficulties. This can lead to acute respiratory and organ failure and wide-spread inflammation, which require hospitalisation and intensive care. Based on global infection fatality rates (IFR), it is estimated that one or two in 1,000 of those known to be infected with this virus may die; this risk increases to around 50 in 1,000 for those aged over 70 years.

Symptoms appear after infection following an incubation period of 2 to 5 days (up to around 14 days) and the virus can be spread for 1 to 2 days prior to any symptoms and peak at around 5 days after symptom onset. Those with symptoms have the most virus and are more likely to spread the infection. However, spread can also occur from those who are incubating the virus (presymptomatic) or those who remain asymptomatic (with no symptoms) but this is less common.  


Apart from supportive medical care, there are no proven treatments for COVID-19. There is increasing evidence that some medications, such as dexamethasone, some monoclonal antibody therapies (tocilizumab) and other anti-inflammatory treatments, can reduce the severity of the disease but there are no treatments currently to stop the disease. Anti-viral medications used for influenza have not been shown to work, but one anti-viral, remdesivir, is used elswhere to treat patients with severe disease and new treatments are in development.


The effects of COVID-19 can range from mild to severe:

  • COVID-19 can be fatal (over 2.5 million people died in one year globally, and numbers have continued to increase with more virulent variants, such as Delta).
  • The risk of severe COVID-19 and death increases with age and in those with chronic health conditions, such as diabetes, obesity and chronic respiratory disease, and including pregnancy. 
  • Long-lasting effects of COVID-19 have been observed, even in those who have had relatively mild symptoms.
  • Preterm birth is a risk for the infants of women who have COVID-19 when pregnant, particularly due to emergency delivery in mothers with breathing difficulties.


  • As part of the pandemic response, the New Zealand Government implemented alert levels to control the spread of SARS-CoV-2 to prevent COVID-19 disease. See Unite Against COVID-19 for further details.
  • Testing for the virus, rapid contact tracing and border restrictions are in place to detect and limit community transmission
  • Good hand-washing hygiene, social distancing and staying home when unwell help to reduce transmission. In some situations, there are limits on the numbers of people in gatherings.
  • Immunisation with a COVID-19 vaccine, has commenced, but it is currently unclear how effective the vaccine is against spread if a vaccinated person encounters the SARS-CoV-2 virus. 

Coronavirus disease 2019 (COVID-19)

Complications of disease

  • Pneumonia
  • Acute kidney and liver injury
  • Neurological – brain inflammation, haemorrhage, seizures
  • Cardiovascular – inflammation of the heart (myocarditis), stroke, heart failure
  • Venous thrombosis – blood clots
  • Acute respiratory failure
  • Multisystem inflammation
  • Post-intensive care syndrome – reduced muscle and brain function
  • Long-COVID syndrome – fatigue, depression, memory loss, cough
  • Death

Responses to vaccine

Common responses

  • Pain at injection site
  • Headache
  • Fatigue
  • Muscle aches
  • Chills
  • Fever
  • Joint aches
  • Nausea

Rare responses

  • Lymphadenopathy (swollen lymph nodes)
  • Myocarditis (in young males after second dose)

 As with any medicine, very rarely, severe allergic reactions can occur following immunisation.

Ministry of Health. About COVID-19. Wellington: Ministry of Health [updated 2021 March 01; cited 2021 March 11)

BMJ Best practice. Coronavirus disease 2019 (COVID-19): Complications BMJ Publishing Group 2021 [last update 2021 Mar 04 ; cited 2021 Mar 10] Available from

World Health Organisation. WHO Coronavirus (COVID-19) Dashboard. [last update daily; cited 2021 Oct 06] Available from


Last updated: Oct 2021