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HomeYour HealthConditionsViral IllnessesWinter Viruses & Viral Illness: What Are The Symptoms & How to Treat ThemWinter Viruses & Viral Illness: What Are The Symptoms & How to Treat Them

Published on May 15, 2023

Authored by Pfizer Medical Team

As we head into the Winter season, you may have developed a scratchy throat, runny nose or cough. Yes, it’s important to be aware that these symptoms could be due to COVID-19 – and a rapid antigen test will confirm this for you. However, other viral infections can also cause similar symptoms. Here, we provide a 101 of common causes of viral illness that you should be aware of.

You may have already noticed that viruses tend to spread with more ease during cooler weather. This phenomenon occurs because people tend to spend more time indoors together during winter (with the windows closed for added warmth). In this type of environment, germs are able to circulate from one person to another through the air or via close contact.1 Whether it is the ‘common cold’, the flu, norovirus, or COVID-19, we have created a symptom checker to help you to identify which virus could be ailing you. Read on to learn more, and remember to always call your local doctor for specific medical advice.

The ‘Common Cold’

What is the common cold?

The ‘common cold’ is a term used to describe a respiratory illness infection which could actually be caused by a range of different types of viruses. Although 20-30% of colds are caused by unidentified bugs, rhinoviruses are known to cause up to 40% of all colds.2 Although these germs frequently circulate during winter and spring, a person may develop a cold at any time of the year.

What are common cold symptoms?

Cold symptoms can be similar to flu symptoms, but they are generally milder. Symptoms include the following:1

  • Runny nose
  • Sore throat
  • Headache
  • Coughing
  • Sneezing
How long do common cold symptoms last?A cold is generally a self-limiting illness. Most people recover from a cold within 7 to 10 days.4When should you see a doctor about your common cold symptoms?If you experience any of the following, you should seek medical advice:1
  • High fever that does not respond to paracetamol
  • No improvement within 48 hours of symptom onset
  • Inability to drink fluids
  • Frequent vomiting
  • Difficulty breathing
  • Any other symptoms that cause concern


What is Influenza?

The flu is caused by the influenza virus. There are many different influenza strains – and these can change each year.5 The flu can be mild or severe - and can cause complications, such as bronchitis (inflammation of the airways of the lungs), pneumonia (infection of the lungs), ear infections, and in severe cases, death.5 Certain groups of people, including babies, pregnant women, older adults and people with underlying health conditions may be at risk of serious complications.
An annual flu vaccine can help prevent you from becoming unwell with the flu.6 Annual flu vaccinations are recommended for all people aged 6 months and older. According to the Australian Immunisation Handbook, influenza vaccination is particularly recommended for children aged 6 months to <5 years; adults 65 years and older, Aboriginal and Torres Strait Islander people; people with medical conditions that increase their risk of influenza; homeless people, pregnant women, healthcare workers and carers; residents, staff and volunteers to aged care and long-term residential facilities; people working in essential community services; and commercial poultry and pork industry workers.6

What are Influenza symptoms?Flu symptoms can be similar to cold symptoms, but they’re generally more severe.5  They can also be similar to COVID-19 symptoms. Common flu symptoms include:5
  • Fever and body chills
  • Sore throat 
  • Cough
  • Headache
  • Runny nose
  • Body aches 
  • Vomiting/diarrhea (more common in children) 
How long do Influenza symptoms last?Some people with the flu will recover within a week5 while others may take several weeks.7 If complications arise, recovery could take longer - and medical assistance may be required. When should you see a doctor about Influenza symptoms?There are many types of flu symptoms that demand medical attention. Some of these are listed below. Always call your doctor if you’re feeling unwell or concerned about any symptoms:7
  • Difficulty with breathing
  • Chest pain
  • Confusion
  • Dizziness
  • Severe vomiting
  • Fever with a rash


What is COVID-19?

COVID-19 is an illness caused by the coronavirus, SARS-CoV-2.8 Similar to the flu, COVID-19 symptoms can range from mild to severe.8  Older adults and people with underlying health conditions (such as diabetes, cardiovascular disease and chronic illness) may be at greater risk of developing serious complications, which may progress to the need for hospitalisation. In some cases, severe COVID-19 may lead to death.9

What are COVID-19 symptoms?

The following list includes a number of potential symptoms, but not all possible symptoms, of COVID-19. If you think you might have COVID-19, it is important that you get tested as soon as possible – either with a PCR test or rapid antigen test – so that you can protect yourself and others.10 If you do test positive, it is important to speak to your doctor as soon as possible - as you may be eligible for oral (at-home) COVID-19 treatment.11

COVID-19 symptoms may include:12 

  • Fever
  • Cough 
  • Shortness of breath/difficulty breathing
  • Muscle/body aches 
  • Lethargy (lack of energy) or weakness 
  • Headache 
  • Loss of/abnormal taste or smell 
  • Sore throat 
  • Runny/stuffy nose 
  • Nausea, vomiting and diarrhea 
How long do COVID-19 symptoms last?

People with mild illness usually recover within 7 days. Some people take longer to recover.13 If you are concerned at any time about your symptoms, it is important to speak to your doctor.  

When should you see a doctor about COVID-19 symptoms? 

COVID-19 can lead to serious complications, and even death. Call for urgent medical help if you experience the following symptoms:12

  • Worsening of symptoms
  • Difficulty breathing 
  • Chest pain
  • Confusion
  • Dizziness/weakness
  • Blue tinge to lips or face
  • Not passing urine
  • Persistent fevers
  • Experiencing any severe symptoms, or worried by your symptoms
  • You are pregnant or have any chronic illnesses


What is Norovirus?

Norovirus refers to a group of viruses that cause acute gastroenteritis (often called stomach flu or gastro bug). Norovirus can spread through contaminated foods and water, or via contact with an infected person.14

What are Norovirus symptoms? 

If you think you may have the stomach flu or gastro bug, it could be norovirus. Common symptoms include:14 

  • Vomiting 
  • Diarrhea 
  • Stomach pain 
  • Nausea 

Other symptoms may include fever, headache and body aches. People with norovirus illness may experience diarrhoea or vomiting multiple times each day. This can increase the chances of developing dehydration. Symptoms of dehydration include dizziness, dry mouth and lack of urination.15 

How long do Norovirus symptoms last? 

Symptoms can develop 12 to 48 hours after being exposed to norovirus. Generally, people with norovirus illness recover in 1 to 3 days.15

When should you call a doctor about Norovirus symptoms? 

You should call a doctor if you experience any of the following:16
•    Bloody stool 
•    Severe vomiting
•    Stomach pain 
•    Dehydration 
•    Diarrhea that continues after several days

Don't forget!

Frequent handwashing and social distancing to help stop the spread of infectious disease. These messages are important for our health generally. To minimise your risk of catching a viral illness:17

  • Wash your hands frequently

  • Disinfect common surfaces regularly (including countertops, doorknobs, remote controls, keyboards and light switches)

  • Use the crook of your elbow or tissue when sneezing  

  • Wear a mask if you are close to other people (such as when using public transport, shopping, or at gatherings)

Where a vaccine is available and recommended, please talk to your local doctor about getting vaccinated to help protect you and your loved ones from these preventable illnesses.


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  2. What's Causing My Cold? WebMD. Accessed  11 May 2023.
  3. Common Cold. Centers for Disease Control and Prevention.,within%20about%207%2D10%20days. Accessed  11 May 2023.
  4. Understanding the Common Cold - the Basics. WebMD. Accessed 11 May 2023.
  5. Influenza (flu). Australian Government. Accessed 11 May 2023.
  6. Influenza (flu). Australian Immunisation Handbook. Accessed 11 May 2023.
  7. nfluenza (flu). Better Health Channel. Accessed 11 May 2023.
  8. COVID-19. Australian Government. Accessed 11 May 2023.
  9. Coronavirus disease (COVID-19). World Health Organization. Accessed 11 May 2023.
  10. Testing for COVID-19. Australian Government. Accessed 11 May 2023.
  11. Oral treatments for COVID-19. Australian Government. Accessed 11 May 2023.
  12. Symptoms of COVID-19 and when to seek medical advice. Healthdirect. Accessed 11 May 2023.
  13. Recovery and returning to normal activities after COVID-19. Healthdirect.,to%208%20weeks%20after%20infection. Accessed 11 May 2023.
  14. Norovirus infection. Healthdirect. Accessed 11 May 2023.
  15. The Symptoms of Norovirus. Centers for Disease Control and Prevention. Accessed 11 May 2023.
  16. Norovirus infection. Mayo Clinic. Accessed 11 May 2023.
  17. Prevent the spread of infectious disease. New Zealand Ministry of Health. Accessed 11 May 2023.
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