Difference between cold, flu and covid

Summary: Cold, flu, and COVID-19 share symptoms but are caused by different viruses and vary in severity. Cold symptoms are typically mild, whereas the flu can cause more serious illness. COVID-19 may lead to serious complications and long-lasting effects. Knowing the differences helps ensure appropriate treatment and prevention through vaccination, hygiene, and early identification.  

With the onset of cold and flu seasons and the ongoing challenges of COVID-19, it’s essential to understand the differences between these three respiratory illnesses. While they have overlapping symptoms, such as coughing and fatigue, their causes, intensity, and treatments differ significantly. Understanding how to differentiate between them can help you take the right action, whether managing symptoms at home or seeking medical help.  

What are the symptoms of cold, flu, and COVID-19?

1. Common cold symptoms:

• Runny or stuffy nose 
• Sore throat 
• Cough 
• Sneezing 
• Mild fatigue 

2. Flu symptoms:

• Sudden fever or chills 
• Cough 
• Body aches 
• Fatigue 
• Sore throat 
• Headaches 
• Runny nose 
• Occasional nausea or vomiting 

3. COVID-19 symptoms:

• Fever or chills 
• Cough 
• Sore throat 
• Fatigue 
• Loss of taste or smell 
• Muscle or body ache 
• Headache 
• Nausea  
• Diarrhoea 
• Congestion or a runny nose 

What are the causes of cold, flu, and COVID-19?

1. Common cold:  

• Cause: The common cold is primarily caused by the rhinovirus, but other viruses like coronaviruses (excluding COVID-19), adenoviruses, and respiratory syncytial virus (RSV) may also trigger it.  
• Transmission: It is transmitted through respiratory droplets released during coughing, sneezing, or touching contaminated surfaces.  

2. Flu (Influenza):

• Cause: The flu is caused by the influenza virus, which includes several types—A, B, C, and D. Types A and B are the most common causes of seasonal flu outbreaks.  
• Transmission: The flu spreads through airborne droplets released when an infected individual coughs, sneezes, or speaks. It can also spread by touching surfaces that have the virus on them.  

3. COVID-19:

• Cause: COVID-19 is caused by the SARS-Cov-2 virus, a coronavirus that emerged in late 2019.  
• Transmission: It primarily spreads through tiny airborne droplets released during talking, coughing, sneezing, or breathing by an infected person; however, airborne transmission can occur in poorly ventilated or corded indoor settings. Surface contact with the virus can also spread it.  

Severity and risk factors

• Cold: Colds are generally mild and resolve on their own. They seldom lead to serious complications. Individuals of all ages can catch colds frequently, but they typically recover within a few days without needing medical care. However, they can exacerbate underlying respiratory conditions such as asthma or chronic obstructive pulmonary disease (COPD). 
• Flu: Influenza often presents more severely than a cold, frequently causing high fevers, chills, and body aches. It can result in complications such as pneumonia, particularly in older adults, young children, pregnant women, and individuals with chronic conditions like asthma, heart disease, or diabetes. 
• COVID-19: COVID can vary from mild to severe and may cause long-term symptoms or serious health issues, especially in older adults, those who are unvaccinated, or individuals with existing health problems. It has a higher hospitalisation and death rate than the cold and flu. 

Testing and diagnosis

• Cold: Colds are typically diagnosed based on symptoms alone, and tests are rarely required unless complications are evident. There are no specific rapid tests available for the common cold. 
• Flu: Rapid flu testing is accessible and can provide results in 10 to 15 minutes, but have variable sensitivity. These tests are usually employed when flu is suspected based on symptoms and the season. Laboratory-based tests give more accurate confirmation. 
• COVID-19: Testing for COVID includes rapid antigen tests in addition to the more sensitive PCR tests. COVID-19 Antigen tests yield quick results but might miss some cases, especially in asymptomatic individuals or during the early stages of infection. PCR tests offer greater accuracy and are frequently used to confirm diagnoses, particularly in symptomatic individuals or those in close contact. 

Treatment options for each

• Cold: There is no cure for the common cold; however, symptoms can be alleviated with rest, hydration, and over-the-counter medications such as decongestants, pain relievers, and cough suppressants. Most individuals recover within a few days. 
• Flu: Antiviral medications, such as oseltamivir (Tamiflu) might be prescribed, especially if administered within 48 hours of symptom onset. Supportive care consists of rest, hydration, and relief from symptoms using pain relievers and fever reducers. 
• COVID-19: Mild cases can be treated at home with rest, fluids, and symptom management. High-risk individuals or severe cases may require antiviral medications, oxygen therapy, or hospitalisation to prevent progression to severe illness. Isolation is crucial to prevent transmission. 

When to see a doctor

• High or persistent fever 
• Trouble breathing or chest pain 
• Confusion or sudden light-headedness 
• Severe sore throat or earache 
• Dehydration or inability to retain fluids 
• Symptoms that worsen after initially improving 

How does telehealth help with cold, flu or COVID-19?

Telehealth in Australia offers fast, convenient access to medical care for cold, flu, or COVID-19 symptoms without leaving home. Through an online doctor consultation, patients can receive advice, instant scripts, or medical certificates for work or school. This helps manage mild to moderate symptoms while reducing exposure to others. Online GP appointments are ideal for discussing fever, sore throat, cough, or COVID-19 concerns. Doctors can recommend tests, antivirals, or home care tips. Available after hours and in remote areas, telehealth services in Australia ensure timely, hassle-free healthcare, keeping communities safer and easing pressure on local clinics and hospitals.

While cold, flu, and COVID-19 exhibit similar symptoms, they are caused by distinct viruses and vary in severity and treatment. Recognising these differences helps ensure proper care and prevention, with vaccination, hygiene, and early detection crucial in limiting their transmission.