# What is the difference between flu and COVID symptoms?

*The Centers for Disease Control and Prevention says the two illnesses share many of their symptoms, and that COVID-19 symptoms can take longer to appear after infection than flu symptoms.*

- Type: Explainer
- Section: Health
- By: Health Desk
- Published: 2026-11-12T01:25:20-05:00
- Updated: 2026-11-12T01:25:20-05:00
- URL: https://factsdesk.com/health/what-is-the-difference-between-flu-and-covid-symptoms/

Topics: [CDC](https://factsdesk.com/topic/cdc/)

## Key facts

- The CDC says a person cannot tell the difference between flu and COVID-19 by the symptoms alone, and that testing is needed to confirm a diagnosis. Source: [Centers for Disease Control and Prevention](https://www.cdc.gov/flu/about/flu-vs-covid19.html). Confirmed 2026-11-12T01:24:30-05:00. Cite: https://factsdesk.com/health/what-is-the-difference-between-flu-and-covid-symptoms/#the-cdc-says-a-person-cannot-tell-the-difference-between-flu
- A change in or loss of taste or smell can occur with both illnesses but is more frequent with COVID-19, according to the CDC. Source: [Centers for Disease Control and Prevention](https://www.cdc.gov/flu/about/flu-vs-covid19.html). Confirmed 2026-11-12T01:24:30-05:00. Cite: https://factsdesk.com/health/what-is-the-difference-between-flu-and-covid-symptoms/#a-change-in-or-loss-of-taste-or-smell-can-occur-with-both
- Flu symptoms typically appear one to four days after infection, while COVID-19 symptoms typically appear two to five days after infection and up to 14 days after, the CDC says. Source: [Centers for Disease Control and Prevention](https://www.cdc.gov/flu/about/flu-vs-covid19.html). Confirmed 2026-11-12T01:24:30-05:00. Cite: https://factsdesk.com/health/what-is-the-difference-between-flu-and-covid-symptoms/#flu-symptoms-typically-appear-one-to-four-days-after
- The CDC says diarrhea is more frequent in children with flu but can occur at any age with COVID-19. Source: [Centers for Disease Control and Prevention](https://www.cdc.gov/flu/about/flu-vs-covid19.html). Confirmed 2026-11-12T01:24:30-05:00. Cite: https://factsdesk.com/health/what-is-the-difference-between-flu-and-covid-symptoms/#the-cdc-says-diarrhea-is-more-frequent-in-children-with-flu
- The CDC's COVID-19 symptom list includes new loss of taste or smell and shortness of breath or difficulty breathing. Source: [Centers for Disease Control and Prevention](https://www.cdc.gov/covid/signs-symptoms/index.html). Confirmed 2026-11-12T01:24:30-05:00. Cite: https://factsdesk.com/health/what-is-the-difference-between-flu-and-covid-symptoms/#the-cdc-s-covid-19-symptom-list-includes-new-loss-of-taste

Flu and COVID-19 cannot be told apart by their symptoms alone, according to the [Centers for Disease Control and Prevention](https://www.cdc.gov/flu/about/flu-vs-covid19.html), which says testing is needed to confirm a diagnosis. The agency says the two share many of their symptoms. The differences it describes are that a change in or loss of taste or smell is more frequent with COVID-19, and that COVID-19 symptoms can take longer to appear after infection. This page reports what the CDC states and is not personal medical advice.

## The symptoms the two illnesses share

The CDC's page on the [similarities and differences between flu and COVID-19](https://www.cdc.gov/flu/about/flu-vs-covid19.html) says both are contagious respiratory illnesses caused by different viruses. Flu is caused by infection with an influenza virus, and COVID-19 is caused by infection with a coronavirus, SARS-CoV-2, the page says. It lists these as common symptoms that the two share:

- Fever or feeling feverish and having chills, with a note that not everyone with flu will have a fever
- Cough
- Shortness of breath or difficulty breathing
- Fatigue (tiredness)
- Sore throat
- Runny or stuffy nose
- Muscle pain or body aches
- Headache
- Vomiting
- Diarrhea
- Change in or loss of taste or smell

## Where the CDC says they differ

The differences the CDC describes are in how often a symptom occurs and when symptoms start, and it does not name a symptom that only one of the two illnesses causes.

| Question | Flu | COVID-19 |
| --- | --- | --- |
| Change in or loss of taste or smell | Can occur | More frequent |
| Diarrhea | More frequent in children | Can occur at any age |
| When symptoms typically appear after infection | One to four days | Two to five days, and up to 14 days |

Every row comes from the CDC's [flu and COVID-19 comparison page](https://www.cdc.gov/flu/about/flu-vs-covid19.html). The same page says that a person with COVID-19 could take longer from the time of infection to experience symptoms than a person with flu.

The CDC's separate symptom pages describe the start of each illness. Its page on the [signs and symptoms of flu](https://www.cdc.gov/flu/signs-symptoms/index.html) says flu symptoms usually come on suddenly. Its page on the [symptoms of COVID-19](https://www.cdc.gov/covid/signs-symptoms/index.html) says symptoms may appear 2 to 14 days after exposure to the virus, and that they may start as mild, with some people progressing to more severe symptoms.

## How each symptom list reads

The CDC keeps one symptom page for each illness, and the lists are worded slightly differently.

| CDC list for flu | CDC list for COVID-19 |
| --- | --- |
| Fever or feeling feverish, chills | Fever or chills |
| Cough | Cough |
| Sore throat | Sore throat |
| Runny or stuffy nose | Congestion or runny nose |
| Muscle or body aches | Muscle or body aches |
| Headaches | Headache |
| Fatigue (tiredness) | Fatigue |
| Vomiting and diarrhea in some people | Nausea or vomiting, and diarrhea |
| Not on the list | Shortness of breath or difficulty breathing |
| Not on the list | New loss of taste or smell |

The left column comes from the CDC's [flu symptoms page](https://www.cdc.gov/flu/signs-symptoms/index.html), which says vomiting and diarrhea are more common in children than adults, and the right column comes from its [COVID-19 symptoms page](https://www.cdc.gov/covid/signs-symptoms/index.html). For more on the flu list, see [What are the symptoms of the flu?](/health/what-are-the-symptoms-of-the-flu/)

## Testing and having both at once

The CDC's [comparison page](https://www.cdc.gov/flu/about/flu-vs-covid19.html) says testing can also show whether someone has both flu and COVID-19 at the same time, which it describes as uncommon. The page says people with both at the same time can have more severe illness than people with either one alone.

## How long each one spreads

The CDC [says](https://www.cdc.gov/flu/about/flu-vs-covid19.html) a person with COVID-19 could be contagious for a longer time than a person with flu.

| Question | Flu | COVID-19 |
| --- | --- | --- |
| Spread before symptoms | About one day before | Two to three days before, on average |
| Period the CDC highlights | Most contagious in the first three days of illness, for older children and adults | Contagious for about eight days after symptoms began, on average |

The page says young children and people with weakened immune systems may be contagious with flu for longer periods of time. For how long flu illness lasts, see [How long does the flu last?](/health/how-long-does-the-flu-last/)

## Emergency warning signs the CDC lists for COVID-19

The CDC's [COVID-19 symptoms page](https://www.cdc.gov/covid/signs-symptoms/index.html) lists these as emergency warning signs for COVID-19:

- Trouble breathing
- Persistent pain or pressure in the chest
- New confusion
- Inability to wake or stay awake
- Lips, nail beds and skin that may appear pale, gray or blue, depending on skin tone

The CDC's emergency warning signs for flu in children and adults are listed on [What are the symptoms of the flu?](/health/what-are-the-symptoms-of-the-flu/)

For how much flu and other respiratory illness is circulating now, see [Is flu and respiratory illness high in my state?](/health/is-flu-and-respiratory-illness-high-in-my-state/) For the months when flu spreads most, see [When is flu season?](/health/when-is-flu-season/)

## Sources

1. [Similarities and Differences between Flu and COVID-19](https://www.cdc.gov/flu/about/flu-vs-covid19.html), Centers for Disease Control and Prevention, 2024-09-17 (primary source)
2. [Symptoms of COVID-19](https://www.cdc.gov/covid/signs-symptoms/index.html), Centers for Disease Control and Prevention, 2025-03-10 (primary source)
3. [Signs and Symptoms of Flu](https://www.cdc.gov/flu/signs-symptoms/index.html), Centers for Disease Control and Prevention, 2024-08-26 (primary source)