People infected with SARS-CoV-2 can transmit the virus to others, even if they do not show symptoms of the disease and are not considered sick

Key takeaway

Scientific evidence indicates that about half of SARS-CoV-2 transmission occurs before infected individuals experience any symptoms of COVID-19. Studies show that asymptomatic carriers, who are people that never develop symptoms of COVID-19, carry as much of the SARS-CoV-2 virus as symptomatic patients and can spread the virus if they do not take adequate measures, such as wearing masks or maintaining physical distance from others.

Reviewed content

Verdict:

Inaccurate

Claim:

“The greatest trick the CDC ever pulled was convincing the world you can be sick without having symptoms”

Verdict detail

Inaccurate: The U.S. CDC has not suggested that people without symptoms, including asymptomatic and pre-symptomatic individuals, are sick. On the contrary, CDC’s recommendations refer to people who are sick and people who are infected but show no symptoms as two distinct groups of people. Both groups can be contagious and must therefore follow the same preventive measures to avoid infecting others.

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Full Claim

“The greatest trick the CDC ever pulled was convincing the world you can be sick without having symptoms”

Hundreds of posts like this one were published on Facebook on and around 23 Aug. 2020 claiming that the U.S. Centers for Disease Control and Prevention (CDC) has “[convinced] the world that you can be sick without having symptoms.” These posts received tens of thousands of interactions in only a few days, according to the social media analytics tool CrowdTangle. The meme is likely a reference to asymptomatic and presymptomatic cases of SARS-CoV-2 infection, the virus that causes COVID-19. This claim is inaccurate, as the CDC has not stated or suggested that people without symptoms are sick.

When a pathogen such a virus infects a person, it starts to multiply in the host without producing apparent signs or symptoms for a period of time. The time interval between infection and the onset of symptoms is called the incubation period, which varies in length depending on the pathogen, the infectious dose received, the site and type of infection, and the immune status of the infected person^[1]. Current evidence indicates that COVID-19 has an incubation period of five to seven days on average, although it can be as long as 14 days in some cases^[2].

The onset of signs and symptoms marks the transition from being presymptomatic to symptomatic. Presymptomatic cases describe infected individuals who appear healthy in the initial stage of infection and display symptoms of illness later, while cases with extremely mild manifestations are called “paucisymptomatic”. In contrast, a true asymptomatic carrier will never develop any symptoms of the disease during the course of the infection, as explained in a previous article review by Health Feedback.

However, presymptomatic, asymptomatic, and paucisymptomatic cases are indistinguishable at the incubation stage of the infection, making it difficult to accurately recognize infected individuals and to assess the contribution of these different groups towards the transmission of COVID-19. For example, someone who tests positive for SARS-CoV-2 and shows no symptoms at the time of testing would be classified as “asymptomatic”, but reclassified as “pre-symptomatic” if they show symptoms later. Furthermore, the lack of evident disease symptoms results in many unreported asymptomatic and paucisymptomatic cases which are not accounted for in scientific studies and statistics.

The medical definition of “sickness” is “the external and public mode of unhealth”^[3]. Hence the condition of being sick requires symptoms to be present. According to this definition, infected people who do not show symptoms would not be considered sick but simply carriers of an infection. Contrary to what the meme claims, the CDC has not suggested that asymptomatic or presymptomatic people are sick. In fact, the CDC refers to people who are sick and infected people as two separate groups, even though it recommends isolation for both groups as they can potentially transmit the infection: “[q]uarantine helps prevent spread of disease that can occur before a person knows they are sick or if they are infected with the virus without feeling symptoms”. Indeed, people with a SARS-CoV-2 infection can be contagious during the incubation period even if they never develop symptoms of the disease^[4]. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, explained during a 10 June interview on the Good Morning America show that “about 25% [to] 45% of the totality of infected people likely are without symptoms”. In line with this, recent estimates from the CDC indicate that around 50% of SARS-CoV-2 transmission occurs during the incubation period before infected individuals experience any symptoms^[5,6].

According to an article published in August in the journal JAMA Internal Medicine, asymptomatic people carried as much virus in their respiratory tract as people showing COVID-19 symptoms^[7]. In fact, the viral load in symptomatic individuals peaked on or before symptoms onset and significantly declined afterwards^[4]. Taken together, these studies indicate that presymptomatic and asymptomatic transmission facilitate the spread of SARS-CoV-2, as people who are unaware that they are infected may not take sufficient precautions to prevent infecting others^[8]. This means that good personal hygiene, physical distancing, and wearing face masks are important for everyone to practice, as these measures help to reduce the spread of infection from infected individuals even before they develop symptoms.

Finally, the U.S. CDC cannot convince or impose its recommendations worldwide since its regulations apply only to U.S states or territories. The organization responsible for monitoring and reporting global health issues is the World Health Organization (WHO). Even so, the WHO can only issue recommendations and it is unable to compel nations to follow its guidelines or sanction countries for not doing so.

In summary, the CDC does not state that people infected with SARS-CoV-2 but who do not show symptoms are sick; rather, the agency warns that these carriers can spread SARS-CoV-2 infection as much as symptomatic patients. Therefore, the CDC recommends that people practice physical distancing and wear masks in public settings to prevent infected people, with or without symptoms of COVID-19, from spreading the virus to others.

REFERENCES

• 1 – Evans. (2009) Epidemiological concepts. Bacterial infections of humans.
• 2 – Qin et al. (2020) Estimation of incubation period distribution of COVID-19 using disease onset forward time: A novel cross-sectional and forward follow-up study. Science.
• 3 – Boyd. (2000) Disease, illness, sickness, health, healing and wholeness: exploring some elusive concepts. Medical Humanities.
• 4 – He et al. (2020) Temporal dynamics in viral shedding and transmissibility of COVID-19. Nature.
• 5 – Wei et al. (2020) Presymptomatic Transmission of SARS-CoV-2 — Singapore, January 23–March 16, 2020. Morbidity and Mortality Weekly Report.
• 6 – Chun et al. (2020) Transmission onset distribution of COVID-19. International Journal of Infectious Diseases.
• 7 – Lee et al. (2020) Clinical course and molecular viral shedding among asymptomatic and symptomatic patients with SARS-CoV-2 infection in a community treatment center in the Republic of Korea. JAMA Internal Medicine.
• 8 – Li et al. (2020) Substantial undocumented infection facilitates the rapid dissemination of novel coronavirus (SARS-CoV2). Science.