Long COVID found even in people who initially were diagnosed with mild COVID-19

Many people who developed serious complications of COVID-19 were hospitalized. Some of the people who survived have gone on to develop long-term complications (called long COVID).

Two separate teams of scientists in the U.S. have done studies on long COVID and reported that it can develop even in people who had mild or uncomplicated COVID-19. The most common manifestation of long COVID in both studies was fatigue.

These and other studies add to the emerging research on long COVID and underscore the need to investigate this issue and develop interventions to help people with long COVID recover.

Study 1

In the first study, a team at Stanford University in California conducted research with 118 participants who had recovered from acute COVID-19. Their average age was 43; 53% were men and 43% were women. A total of 22 participants had required hospitalization when they were diagnosed with COVID-19.

Three to four months after their initial diagnosis of acute COVID-19 (when any hospitalizations would have occurred), researchers found that many participants had symptoms of long COVID, distributed as follows:

  • formerly hospitalized people – 82%
  • not hospitalized – 64%

Common symptoms of long COVID were as follows:

  • fatigue
  • shortness of breath
  • loss of sense of taste and/or smell
  • muscle pain or soreness
  • memory problems
  • chest pain
  • loss of hair

Having shortness of breath at the onset of COVID-19 was linked to a greater risk of subsequently having two or more symptoms of long COVID.

Many participants had some degree of impairment caused by symptoms of long COVID that affected their productivity at work.

Study 2

Another team of scientists, this time at the University of Washington in Seattle, has been monitoring 177 participants with and without COVID-19 for up to nine months. Their average age was 57; 57% were men and 43% were women.

The researchers categorized participants as follows:

  • formerly hospitalized with COVID-19 – 16 people
  • diagnosed with COVID-19 but not hospitalized because of mostly mild symptoms – 150 people
  • diagnosed with SARS-CoV-2 infection and remained symptom free – 11 people

Over the course of the study, about 30% of people who were first diagnosed with acute COVID-19 had persistent symptoms of long COVID. This figure was similar regardless of whether or not they had been hospitalized.

Common symptoms of long COVID in this study were as follows:

  • fatigue
  • loss of sense of smell and/or taste

Four people reported problems with thinking clearly and memory (brain fog).

Nearly 30% of people with long COVID reported poor health-related quality of life.

Although both studies are relatively small, they confirm general findings from other studies and reports that long COVID can occur later even in some people who had a mild course of COVID-19.

—Sean R. Hosein


  1. Jacobson KB, Rao M, Bonilla H. Patients with uncomplicated COVID-19 have long-term persistent symptoms and functional impairment similar to patients with severe COVID-19: a cautionary tale during a global pandemic. Clinical Infectious Diseases. 2021; in press.
  2. Logue JK, Franko NM, McCulloch DJ, et al. Sequelae in adults at 6 months after COVID-19 infection. JAMA Network Open. 2021 Feb 1;4(2):e210830.