The Incubation Period of Coronavirus Disease 2019

Reviewed by Charles Li

February 17, 2022

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Question

How long does it take for COVID-19 symptoms to appear?

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Answer

On average, around five days. But, for some, it can take up to two weeks.

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How they did it

Researchers tracked 181 of the first cases of COVID-19 in China to see when they got exposed to COVID-19 and when they first showed symptoms.

Visual Abstract

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Background

Study Quote

Lauer et al, 2020, Ann Intern Med.

A novel human coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), was identified in China in December 2019. There is limited support for many of its key epidemiologic features, including the incubation period for clinical disease (coronavirus disease 2019 [COVID-19...

At the start of the COVID-19 pandemic, scientists sought to answer key questions about COVID-19, such as how infectious the virus was, how quickly the virus could spread, and how we could use this information to stop the spread.

This was one of the first studies to estimate the incubation period of COVID-19. The paper was published just a few months after the discovery of COVID-19.

It provided one of the best estimates on the infectiousness and timing of COVID-19.

Many of the recommendations you've probably heard about COVID-19, such as isolating after coming in contact with someone with COVID-19, come from this paper, among others.

Method

Study Quote

Lauer et al, 2020, Ann Intern Med.

Objective: To estimate the length of the incubation period of COVID-19 and describe its public health implications. Design: Pooled analysis of confirmed COVID-19 cases reported between 4 January 2020 and 24 February 2020.Setting: News reports and press releases from 50 provinces, regions...

This study examined 181 of the first cases of COVID-19 outside of Wuhan in China.

The researchers looked for early cases where they could precisely identify where the patient got infected, what symptoms they had, and when they had them.

In the early days of the pandemic, there were far fewer people who had active cases of COVID-19, which allowed scientists to trace where patients got infected. Today, this task is more difficult with the rapid growth of COVID-19, which is why this early data can be a valuable tool in understanding the pandemic.

Results

Study Quote

Lauer et al, 2020, Ann Intern Med.

There were 181 confirmed cases with identifiable exposure and symptom onset windows to estimate the incubation period of COVID-19. The median incubation period was estimated to be 5.1 days (95% CI, 4.5 to 5.8 days), and 97.5% of those who develop symptoms will do so within 11.5 days (CI,...

Researchers found that after someone gets exposed to COVID-19, it takes around five days for symptoms to show up.

Before five days, many individuals may feel perfectly fine and won't know they got infected. However, they can still spread COVID-19 during this time before knowing that they themselves are infected.

This estimate was precise, with a small margin of error, and is consistent with other similar estimates for COVID-19.

This "incubation period" can vary widely from person to person. While around half of people infected with COVID-19 will show symptoms within five days, some people can take longer to develop symptoms.

Around 97.5% of people will develop symptoms by 11.5 days. By 14 days, according to the researcher's models, 99% will show symptoms.

Many travel quarantine requirements, which can take up to two weeks, are based on this data.

Study Figure 2

The chart above shows estimates of how long it takes for COVID-19 symptoms to show after infection.

The large majority of people with COVID-19 will show symptoms between 4-6 days.

Fewer than 3% of people with COVID-19 will show symptoms within two days. A few individuals will take closer to two weeks to show symptoms.