Cold, Flu, or COVID? How to Tell the Difference & When to See a Doctor

Is it a cold? Flu? Or COVID-19? When self-diagnosis is difficult, seek medical attention early.

Many of you have probably experienced thinking, "I have a fever, but is it a cold? Or the flu? Or COVID-19?" and then missing the opportunity to go to the hospital. Since the symptoms are similar, it's quite difficult to make a self-diagnosis, and there are cases where symptoms worsen while waiting it out with over-the-counter medications. This article will clearly explain the differences in symptoms between colds, influenza, and COVID-19, and when you should seek medical attention.

Characteristics of Colds, Influenza, and COVID-19

Colds (Common Cold)

Colds are caused by over 200 types of viruses, including rhinoviruses and certain types of coronaviruses. Symptoms primarily include a sore throat, runny nose, sneezing, and a mild cough. Fever rarely exceeds 38 degrees Celsius, and general malaise is often not very severe. Symptoms tend to appear gradually, and it typically resolves naturally within about a week.

Influenza (Flu)

Influenza is an infection caused by the influenza virus, and the big difference from a cold is the speed of onset and severity of symptoms. A sudden high fever of 38-40 degrees Celsius appears, accompanied by joint pain, muscle aches, headache, and severe fatigue all at once. The feeling of "I was fine yesterday, but I can't move today" is typical. Throat and nasal symptoms may be milder than with a cold, but the overall impact on the body is significant. Special care is needed for complications like pneumonia, especially in the elderly, young children, and those with pre-existing conditions.

COVID-19 (Novel Coronavirus Infection)

COVID-19 symptoms vary depending on the variant, and current dominant strains often present with symptoms quite similar to a cold or the flu. Fever, sore throat, runny nose, cough, and fatigue are the main symptoms. What differs from the flu is that symptoms often progress relatively slowly. Olfactory and gustatory dysfunction, previously considered characteristic, are less common with recent variants but can still occur rarely. Due to its high infectivity, it's important to confirm early to prevent its spread in workplaces and homes.

Comparing Symptoms

Symptom	Cold	Influenza	COVID-19
Fever	Mild fever ~38°C	38-40°C (sudden onset)	37-39°C
Onset	Gradual	Sudden (worsens in hours)	Somewhat gradual
Sore throat	Strong	Can occur	Often strong
Runny/stuffy nose	Common	Less common	Can occur
Cough	Yes (mild)	Yes	Yes (can linger)
Headache	Mild	Strong	Can occur
Joint/muscle pain	Almost none	Strong	Can occur
Severe fatigue	Mild	Very strong	Can occur
Loss of smell/taste	None	None	Rarely occurs

However, this table is merely a guideline. In reality, symptoms often overlap, and it's frankly "difficult to judge even looking at the table." Especially for influenza and COVID-19, it's often impossible to distinguish them by symptoms alone, so testing is the most reliable way to confirm.

Confirmation by Testing

Our clinic offers the following in-house tests, and results can be provided in about 5-10 minutes.

• Influenza antigen qualitative test (nasopharyngeal swab)
• COVID-19 antigen qualitative test (nasopharyngeal swab)
• Simultaneous influenza and COVID-19 test
• Mycoplasma test (for those with persistent coughs)

Even in cases where an over-the-counter test kit at home was negative but symptoms persist, we recommend coming in for a clinic test, as it has higher accuracy. Especially if the test is taken too soon after onset, over-the-counter kits may not show a reaction.

Seek Medical Attention Early in These Cases

Even if you tend to think, "I'll wait and see a little longer," please visit the clinic early if any of the following apply:

• Persistent high fever of 38.5 degrees Celsius or higher
• Fever does not go down even with antipyretics, or quickly returns
• Difficulty breathing or chest pain
• Unable to drink fluids or eat anything at all
• Feeling lethargic and unable to get up
• Impaired consciousness or slurred speech
• Aged 65 or over, pregnant, or have pre-existing conditions (e.g., diabetes, heart disease, lung disease)
• Young child with a sudden high fever
• Fever has lasted for 4-5 days or more

Especially if you experience "difficulty breathing" or "chest pain," pneumonia or other complications may be suspected, so please seek medical attention as soon as possible.

When is it okay to "wait and see"?

Conversely, if you are in the following condition, resting at home and observing your symptoms is one option:

• Mild fever in the 37-degree Celsius range, and you are able to eat and drink fluids
• You have a sore throat or runny nose, but it's not severe enough to disrupt daily life
• Symptoms are somewhat alleviated by over-the-counter fever reducers or nasal decongestants

However, if symptoms do not improve after 2-3 days, or if they worsen, we recommend visiting the clinic without hesitation. There's no need to feel it's a "waste." Acting early often leads to a quicker recovery in the long run.

Treatment for Influenza and COVID-19

Influenza

If antiviral drugs (such as Tamiflu, Inavir, Xofluza) are started within 48 hours of onset, the duration of symptoms can be shortened. Many people delay seeking treatment, thinking "it might be too late," but the earlier you get tested, the more effective the treatment, so it's important to get tested as soon as possible.

COVID-19

For mild cases, treatment is generally symptomatic (medication to alleviate symptoms). However, for individuals at high risk of severe illness (elderly, pregnant women, those with underlying conditions), antiviral drugs may be prescribed. If you test positive, our clinic will also advise you on how to manage your isolation period.

Colds

Unfortunately, there is no specific cure for the common cold; the basic approach is rest, hydration, and sleep. However, if symptoms are severe, antipyretics, nasal decongestants, and cough suppressants can be prescribed to make you more comfortable. Many people think, "If I go to the hospital, they'll just give me cold medicine," but having medication tailored to your symptoms can make a significant difference.

It's perfectly fine to come in with a fever.

Some people hesitate to visit the clinic when they have a fever, but our clinic accepts patients with fever. If you have antipyretics, please take them before coming. If you inform us at the reception, we will take measures to minimize the risk of infection to other patients.

Making a reservation online or by phone will ensure a smoother process. It would be helpful if you could inform us in advance that you have a fever.

Frequently Asked Questions

Q. My family member tested positive for COVID-19. I don't have symptoms, can I get tested?
If you don't have symptoms, testing under health insurance may be difficult. Please call us first to discuss. We will guide you according to your situation.

Q. I tested negative, but my symptoms persist. What should I do?
Sometimes, tests may not detect the virus immediately after onset. You can get retested after 2-3 days, or if symptoms continue, please visit us to investigate other possible causes.

Q. My child suddenly has a high fever. Can we come in right away?
Yes. We accept children with fever. Making a reservation online or by phone will ensure a smoother process.

Q. Are flu medications available over-the-counter?
Antiviral drugs (like Tamiflu) are prescription-only medications. They cannot be purchased over-the-counter, so you need to visit a clinic to get a prescription.

For those with fever and cold symptoms in Jujo, Akabane, Higashi-Jujo, and Oji

Halu Clinic is located about 1-2 minutes walk from JR Saikyo Line Jujo Station, and is open daily from 9 AM to 9 PM, including weekends and holidays. It is conveniently located for patients coming from Akabane, Higashi-Jujo, Oji, Shimo, Itabashi, and Toshima areas.

If you're wondering, "Is it a cold? Flu? Or COVID-19?", the best thing to do is to visit and get checked. The sooner the cause is identified, the sooner appropriate treatment can begin. You can visit without a reservation, but we prioritize those with online reservations.

Book Online Here　／　 Access & Clinic Hours　／　 Contact Us on LINE

Halu Clinic | 1F J&MALL, 2-27-1 Kamijujo, Kita-ku, Tokyo 114-0034
TEL: 03-6698-2509 ／ Clinic Hours: Daily 9:00〜21:00 (Irregular holidays)