Facts about coronavirus (COVID-19)

The science behind coronavirus (COVID-19).

Coronavirus (COVID-19) is a new disease that the world is still learning about. New research is happening all the time so we can understand more about the disease, including the long-term effects.

What are the symptoms of coronavirus (COVID-19)?

Dial 000 if you are having trouble breathing or have chest pain.

If you have any of the symptoms listed below, however mild, you should seek advice and get tested immediately.

To get further advice, call the 24-hour coronavirus hotline 1800 675 398 or see your general practitioner.

The symptoms to watch out for are:

  • loss or change in sense of smell or taste
  • fever
  • chills or sweats
  • cough
  • sore throat
  • shortness of breath
  • runny nose

Some people may also experience headache, muscle soreness, stuffy nose, nausea, vomiting and diarrhoea.

What are the long-term effects of coronavirus (COVID-19)?

Coronavirus (COVID-19) only emerged in late 2019, so the world is still learning about this virus. It may take years before we fully understand its long-term effects.

Recent research is still unclear about how many people who have recovered from the virus experience long-term symptoms.

The most common long-term symptoms are:

  • fatigue
  • shortness of breath
  • chest pain or discomfort
  • inability to concentrate
  • reduced ability to smell.

In some people, coronavirus (COVID-19) may cause long-term damage and inflammation to the lungs, heart, kidneys and brain.

This is why it is important to protect yourself and others by washing your hands regularly, wearing a face mask and maintaining physical distance of at least 1.5 metres. See Staying safe page for more information.

What is the latest information on immunity to coronavirus (COVID-19)?

When infected with a virus like coronavirus (COVID-19), it is common for people’s bodies to develop defences that give the body immunity and provide protection from getting the same virus again. As this coronavirus is new, we don’t yet understand how long such immunity lasts.

Some coronavirus (COVID-19) research shows that immunity levels may decrease a few weeks after recovery, and people who experience milder symptoms may develop less immunity.

As of October 2020, only nine instances of reinfection have been reported globally out of 44 million reported coronavirus (COVID-19) infections around the world. In these cases, tests found that the first and second infections were separate occurrences and not a continuation of the same infection.

In most of the reported cases of reinfection, the first infection caused only mild symptoms or the person was asymptomatic, but the second infection (reinfection) caused worse symptoms.

In one case the person was symptomatic in the first infection but asymptomatic throughout the second infection.

Research suggests that having milder symptoms in the second infection suggests the immune system has developed from the first infection and is responding quickly to keep symptoms at bay. Having more severe symptoms in the second infection suggests the response from the immune system is making the disease worse – this is called ‘antibody-dependent enhancement’.


  • Vaccines are easier to create for diseases where the initial infection leads to lasting immunity, but this is not essential. If immunity declines over time or is not always complete, then booster shots may be needed.
  • Reinfection cases are still rare and more research and data is needed before we can understand its implications.

With more testing, monitoring and research worldwide, our understanding may change.

How is coronavirus (COVID-19) transmitted?

As coronavirus (COVID-19) is a new virus, new scientific research is regularly emerging. Currently, the World Health Organization suggests that coronavirus (COVID-19) can be transmitted by contact with droplets or airborne aerosols from an infected person, and contaminated surfaces. Airborne aerosols are tiny particles that float in the air. This understanding may change as more research emerges and we learn more about coronavirus (COVID-19).

Droplet transmission

A person can be infected with coronavirus (COVID-19) by touching respiratory droplets like saliva or tears from an infected person. These are spread through coughing, sneezing, kissing, talking or singing.

These droplets can enter your mouth, nose or eyes and cause infection. This can happen by having close face-to-face contact, being within 1.5 metres of someone with coronavirus (COVID-19), or by touching a contaminated surface before touching your face.

Airborne transmission

Saliva or tears from an infected person can stay in the air after they cough, sneeze, talk or even sing. This means that coronavirus (COVID-19) can be spread through these tiny infectious particles suspended in the air.

Sometimes, the virus can remain in the air for some time in settings such as in indoor spaces with poor ventilation.

Contaminated surfaces transmission

Coronavirus (COVID-19) can spread when secretions or droplets from an infected person land on surfaces. The virus can live on surfaces for hours or days, depending on the temperature, humidity, type of surface, and how much of the virus is present.

If you touch an infected surface, you could become infected by then touching your nose, mouth or eyes. You could also spread the virus from one surface to another and infect other people.

What is the treatment for coronavirus (COVID-19)?

In some patients who require oxygen therapy, dexamethasone (a corticosteroid) has been used to reduce the severity of illness. This treatment does not work for people who do not need oxygen and should only be used under the direction of a treating doctor.

Early diagnosis, testing and general supportive care are important.

What is the difference between coronavirus (COVID-19) and the flu?

The virus (called SARS-CoV-2) that causes coronavirus (COVID-19) is different from the virus that causes influenza (flu).

Coronavirus (COVID-19) is a more severe disease than seasonal influenza. Globally, about 2 to 4 per cent of people reported to be infected with coronavirus (COVID-19) have died. By comparison, fewer than 1 per cent of those infected die from seasonal flu.

Around the world, many people have built up immunity to seasonal flu strains, but coronavirus (COVID-19) is a new virus and no one has developed immunity before being exposed, making everyone susceptible to infection. Research is underway to investigate how long immunity lasts for people who have recovered from coronavirus (COVID-19) symptoms.

The respiratory symptoms caused by the two illnesses can be similar and you can avoid catching both by keeping at least 1.5 metres between yourself and others, washing your hands often, and coughing or sneezing into your elbow or a tissue. Find out more ways you can slow the spread of coronavirus (COVID-19)

How do I protect myself against the flu?

  • Wash your hands often and cough or sneeze into your elbow or tissue.
  • The flu shot is available at your local GP or community immunisation session. Many accredited pharmacies can also provide the flu shot and advice about the virus. We suggest calling ahead to your local immunisation provider to ensure they have stock available and to book your appointment.

For more information about the flu shot, see Flu (influenza) – immunisation page on the Better Health Channel.

Does coronavirus (COVID-19) survive on surfaces?

Studies suggest that coronavirus (COVID-19) may persist on surfaces for a few hours or up to several days. How long may vary depending on the temperature, humidity, type of surface, and how much of the virus is present.

If you think a surface may be infected, clean it with a common household disinfectant.

Clean your hands with an alcohol-based hand sanitiser or wash them with soap and water often, for 20 seconds. Avoid touching your eyes, mouth, or nose.

How do we know that people who have had coronavirus (COVID-19) are no longer infectious?

People who test positive for coronavirus (COVID-19) must stay in isolation until they are no longer experiencing symptoms and a suitable amount of time has passed.

The Department of Health will provide clearance for when a person who has had coronavirus (COVID-19) can stop isolating.

For more information on isolation, see What to do if you have coronavirus (COVID-19).

Can pets be infected with coronavirus (COVID-19)?

There have been no reports of coronavirus (COVID-19) in domestic animals or wildlife in Australia.

It has been reported overseas that cats, dogs and ferrets can contract coronavirus (COVID-19) if they have significant exposure to infected humans. Cats and ferrets may even become ill, but this is very rare. There is no evidence that domestic or wild animals can spread coronavirus (COVID-19) to humans.

Coronavirus (COVID-19) spreads through close contact with an infected person; mostly face-to-face or within an enclosed space.

If you are sick with coronavirus (COVID-19), you should minimise contact with animals and where possible you should arrange for someone else to mind your pets and care for livestock.

Remember, animals need to be looked after during the coronavirus (COVID-19) pandemic too. For more information regarding domestic pets, see Australian Veterinary Association advice: Coronavirus (COVID-19): AVA updates. For those in the farming and agricultural sector, see: Coronavirus (COVID-19) page in Agriculture Victoria website.

What is viral shedding?

A person with coronavirus (COVID-19) has infected cells in their body which release the virus into the environment. This process – viral shedding – occurs when someone ‘sheds’ coronavirus (COVID-19) by breathing, sneezing or coughing, or through their faeces and urine. 

After recovering from coronavirus (COVID-19), some people can have non-infectious fragments of the virus left in their bodies for some time. These fragments may still return a positive result in a test for the virus, although this result may be weak and prompt further testing to confirm they are no longer infectious (not an active or new case). 

How long does coronavirus (COVID-19) shedding last?

Viral shedding of fragments that are infectious usually begins within a few days of contracting the virus, whether people have symptoms or not. If they do have symptoms, people with coronavirus (COVID-19) typically stop respiratory shedding by day 10 after the first onset of symptoms, or three days after symptoms resolve.

Contact tracing, isolation and quarantine instructions are based on our current understanding of this infectious period.

Viral shedding of fragments that are not infectious can continue for longer periods, especially after severe cases of coronavirus (COVID-19). A recent review of global data suggests that shedding of coronavirus (COVID-19) fragments can persist for more than 80 days from the respiratory tract and more than 120 days in faeces, although this can vary considerably.  

More scientific studies on coronavirus (COVID-19) will see our knowledge about viral shedding continue to grow. 

Why do some people shed the virus for longer? 

Research is underway to understand more about people who shed viral fragments for longer than the typical period.

Early studies suggest that some groups of people including males, children, older adults and people who are immunocompromised may be more likely to shed virus for longer.

The amount of virus in the body (viral load) is higher in people with severe coronavirus (COVID-19) and remains higher for longer than in people with mild cases. 

Can viral fragments be detected in wastewater? 

Yes, viral fragments can be detected in wastewater. In Victoria, wastewater is tested for coronavirus (COVID-19) weekly and a positive test result may indicate there is an active case of coronavirus (COVID-19) in the community, or that someone who is no longer infectious is continuing to shed fragments of the virus.

Find out about wastewater monitoring in Victoria and what it means for your community.

Resources/further reading

Our information draws on recent research published:

Reviewed 29 April 2021

Coronavirus Victoria

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