As monsoon or seasonal transitions hit, respiratory illness cases will surge — with overlapping symptoms, it can be challenging to tell the illnesses apart. COVID-19, Influenza (Flu), and respiratory syncytial virus (RSV) can share symptoms of cough, fever, fatigue, and other symptoms, but these three infections differ in how they present, how severe they are, and who is most impacted by the infection. Being aware of the key signs can help you receive proper treatment, isolation, and avoid complications from the infection, especially if you are acting as a caregiver for vulnerable groups like infants or the elderly.
According to Delhi-based Internal Medicine Specialist Dr. Sameer Khanna, keeping these key differences in mind can help you better manage your illness. Here are the differences between the three illnesses:
Also Read: Viral, Dengue or Typhoid? Spot the difference in common monsoon fevers
1. Development of Symptoms
Flu: Starts very suddenly — you could feel completely fine in the morning and be bedridden by the evening
COVID-19: Gradual onset of symptoms over couple of days
RSV: Lately gradual, you may think it is a mild cold at first
2.Loss of smell or taste
COVID-19: Main symptom (especially in earlier variants)
Flu & RSV: Can occur, but rarely unless from nasal congestion causing loss of smell
3.Onset of Symptoms
Flu: Comes on suddenly — you might feel fine in the morning and be bedridden by evening.
COVID-19: Gradual onset over a couple of days.
RSV: Slow onset, often mistaken for a mild cold at first.
4.Loss of Taste or Smell
COVID-19: A hallmark symptom, especially in earlier variants.
Flu & RSV: Rarely causes this unless due to nasal congestion.
5.Respiratory Symptoms
RSV: Predominantly wheezing, chest congestion, and breathing difficulty — especially in infants and older adults.
Flu: Dry cough and sore throat.
COVID-19: Dry cough, which can at times progress to shortness of breath in severe cases.
6.The Fever
Flu: Sudden onset high fever (up to 102–104°F).
COVID-19: Moderate fever, varies case to case.
RSV: Low-grade fever or none.
7.Age Group Focus
RSV: Most dangerous for infants (less than 1 year) and older adults.
Flu and COVID-19: All age groups can be affected, but severity is often related to whether someone is an older adult or has comorbidity factors.
8.Fatigue and Body Aches
Flu: Often associated with extreme body aches and feeling exhausted.
COVID-19: Fatigue is a normal symptom and can be prolonged ("long COVID").
RSV: Minimal amount of fatigue and more respiratory related symptoms.
9.Duration of Illness
Flu: 5-7 days with improvement by the end of the week.
COVID-19: Symptoms can last 10-14 days, and may include lingering fatigue, cough.
RSV: 1-2 weeks, although the RSV infection can cause complications like bronchiolitis or pneumonia.
Testing (PCR or rapid antigen) will provide confidence about which virus you had; however, understanding these distinctions allows you to seek timely care and to protect others from being infected. If symptoms persist or worsen, see a doctor.
Disclaimer: This article, including health and fitness advice, only provides generic information. Don’t treat it as a substitute for qualified medical opinion. Always consult a specialist for specific health diagnosis
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