The difference between influenza and COVID-19 and SARS: how to determine by symptoms and what to take in each case

The article is for informational purposes only and does not replace a doctor’s consultation. An accurate diagnosis is made only by a doctor, treatment is prescribed only by a specialist. Do not self-medicate.

Introduction: Why we confuse influenza, SARS and COVID-19

Influenza, COVID-19 and SARS cause similar symptoms: runny nose, cough, fever, weakness. In everyday life, all this is often called a “cold”, although the risks and treatment tactics vary. This article does not teach you how to make a diagnosis on your own, but helps you understand when you can be monitored at home, when you need a family doctor, and in what cases you need emergency care.

Briefly about each disease

SARS / “cold”

SARS is a variety of viruses that mainly affect the upper respiratory tract. Usually it begins gradually: sore throat, runny nose, sneezing, moderate fever. The condition is often mild, but in children, the elderly and people with chronic diseases, even a “cold” can cause complications.

Influenza

Influenza is caused by influenza viruses A and B. It starts abruptly: high fever rises quickly, chills, aches in muscles and joints, severe weakness, headache appear. The risk of complications (pneumonia, exacerbation of chronic diseases) is higher than with a conventional SARS.

COVID-19

COVID-19 is caused by the SARS-CoV-2 virus. The course varies from mild runny nose and cough to severe pneumonia with respiratory failure. Prolonged cough and weakness are often noted, sometimes loss of smell and taste, shortness of breath, blood clotting and heart disorders.

The main symptoms of COVID-19, influenza and SARS

What’s in common

For all three infections, fever, cough, runny nose, sore throat, weakness, headache are possible. It is impossible to accurately distinguish one disease from another by these symptoms alone – the general context and the doctor’s examination are important.

What happens more often with COVID-19, influenza and SARS

With influenza, a sudden onset, high fever, severe aches and fatigue, headache, and eye pain are typical. With SARS in the center, runny nose, sneezing, nasal congestion, moderate fever, the general condition suffers less. With COVID-19, both a flu-like onset and a more erased picture are possible, often with a prolonged dry cough, shortness of breath, loss of smell and taste, severe fatigue, and sometimes gastrointestinal symptoms.

How to distinguish influenza, COVID-19 and SARS by symptoms

Nature of onset and severity of symptoms

Flu: a sharp start, a few hours later – high fever and poor health. SARS: gradual development, first throat and runny nose, then moderate fever. COVID-19: variants from a mild “cold” to a severe infection; Prolonged cough, shortness of breath, loss of smell, and pronounced weakness are alarming.

When the symptoms cannot be solved

If the symptoms overlap (fever, cough, runny nose) and there is no vivid typical picture, it is impossible to determine by sensations – you need a family doctor and, if necessary, laboratory tests.

A brief algorithm of actions at the first symptoms

1. Stay at home: cancel work/study, limit contacts.
2. Evaluate the “red flags”: shortness of breath, chest pain, confusion, convulsions, blue lips, sharp deterioration – if there is at least one sign, call an ambulance.
3. If there is no threat, contact your family doctor (by phone, online or in person). Describe the symptoms, duration, possible contacts.
4. Take tests (PCR or rapid COVID-19/flu tests) as prescribed by your doctor.
5. Follow the recommendations for treatment and monitoring. Do not add medicines “on your own”.
6. Monitor the condition on the 5th-8th day: if it worsens (new fever, increased cough, shortness of breath), consult a doctor again.

When you urgently need to see a doctor and call an ambulance

An ambulance includes situations when the following appear:

• pronounced shortness of breath, difficulty breathing at rest;
• pain, tightness, or burning sensations in the chest;
• confusion, strange behavior, difficulties with contact speech response;
• convulsions, loss of consciousness;
• blue lips, face, nails or pronounced pallor;
• very high fever that does not decrease against the background of antipyretic, especially in children and the elderly;
• sharp deterioration on the 5th-8th day of the disease after a period of improvement.

In young children, pregnant women, the elderly and people with severe chronic diseases, it is better to seek help earlier and not wait for pronounced threatening symptoms.

Diagnosis: how to confirm what exactly you are sick with

Why symptoms alone are not enough

The symptoms of influenza, COVID-19 and SARS often coincide, and the course is atypical. Therefore, it is often impossible to say exactly which virus caused the disease from complaints and even an examination alone. To decide on the tactics of treatment and isolation, the doctor uses laboratory methods.

Main methods

• PCR test: detects the genetic material of the virus (SARS-CoV-2, influenza viruses, etc.).
• Rapid antigen tests: Rapid tests for COVID-19 and/or flu, usually in 10 to 15 minutes.
  The decision on what and when to take the test is made by the doctor, taking into account the duration of symptoms and the epidemiological situation.

Additional examinations in case of complications

Complications of influenza, COVID-19 and other SARS are most often associated with pneumonia, exacerbation of chronic lung diseases and respiratory failure. If they are suspected, symptoms alone are not enough, so the doctor prescribes additional examination methods.

These include:

• chest X-ray or CT scan to detect pneumonia and assess the extent of the lesion;
• general and biochemical blood tests, markers of inflammation and clotting;
• saturation measurement (SpO₂) to assess respiratory failure;
• if necessary, an ECG and other tests if there are complaints from the heart.

These methods help to confirm or rule out complications and decide whether a hospital and more intensive treatment are needed.

What is usually done for each disease

General approaches to SARS

Basic set: rest, sufficient drink, ventilation and humidification of the air, light food, symptomatic drugs (antipyretics, nasal drops, throat medications) on the recommendation of a doctor. Antibiotics are not needed for an uncomplicated “cold”.

General approaches to influenza

Same base, but stricter regimen and surveillance, especially for people at risk. In the first days of the disease, the doctor may prescribe antiviral drugs active against influenza viruses, if there are indications and the deadlines are met. If shortness of breath, chest pain or a sharp deterioration appears, immediately consult a doctor or hospital.

General approaches to COVID-19

In case of a mild course: home isolation, drinking, ventilation, symptomatic treatment as prescribed by a doctor. For risk groups, it is important to control saturation and closely monitor shortness of breath and weakness. In severe cases and in patients with risk factors, the doctor decides on specific antiviral therapy and hospitalization.

Prevention: what really works

Vaccination

Flu vaccination (annually) and vaccination against COVID-19 reduce the risk of severe disease and complications. A specific vaccination regimen is selected with a doctor according to current recommendations.

Hygiene and regime

Regular hand washing, use of antiseptic, ventilation of rooms, reduction of overcrowding and, if necessary, wearing masks in closed crowded places help reduce the spread of respiratory infections.

Lifestyle

Adequate sleep, exercise, a varied diet, smoking cessation and a moderate attitude to alcohol support the normal functioning of the immune system. The advertised “immunomodulators” and dietary supplements without a doctor’s prescription do not replace these measures.

FAQ

Is it possible to understand for sure that I have the flu, COVID-19 or SARS by one symptom?

No. The same symptom (such as cough or fever) occurs in different infections. The diagnosis is made by a doctor, focusing on the whole picture and, if necessary, the test results.

If the test is negative, but there are symptoms, what to do?

A negative test does not always rule out COVID-19 or influenza: much depends on the timing and quality of the material sampling. If you feel unwell or have been in contact with the patient, discuss with your doctor repeated testing and further tactics.

How long is a person contagious with the flu and COVID-19?

On average, a person with the flu is contagious about a day before the onset of symptoms and about a week after the onset of the disease. With COVID-19, the virus often begins to be shed 2-3 days before symptoms, and contagiousness persists for about 8-10 days, longer in severe cases and in people with immunodeficiencies.

When is a family doctor enough, and when do you need an ambulance?

In case of moderate symptoms without shortness of breath and severe weakness, consult your family doctor. If there are “red flags” (shortness of breath, chest pain, confusion, convulsions, sudden deterioration), call an ambulance.

Conclusion

Influenza, COVID-19 and SARS are similar in appearance, but differ in risks and possible complications. Do not try to guess the diagnosis from Internet tables: it is more important to stay at home in time, limit contacts, assess alarming symptoms and contact a doctor. Prevention and respect for one’s health often work better than late attempts to “catch up” with the disease.

References

1. Ministry of Health of Ukraine. GRVI, grip and COVID-19: as a rozrezniti zavoryuvannya ta koli zvertatsya do likarya. (https://moz.gov.ua/uk/grvi-grip-ta-covid-19-jak-rozrizniti-zahvorjuvannja-ta-koli-zvertatisja-do-likarja-)
2. Centers for Disease Control and Prevention (CDC). Similarities and Differences Between Flu and COVID-19. (https://www.cdc.gov/flu/about/flu-vs-covid19.html)
3. Centers for Disease Control and Prevention (CDC). How Flu Spreads and the Flu Infectious Period. (https://www.cdc.gov/flu/spread/index.html)

Author: Natalia Kandybey, Candidate of Pharmaceutical Sciences, Quality Director of PJSC Pharmaceutical Factory “VIOLA”

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