Skip to main content

Natural History of Asymptomatic SARS-CoV-2 Infection

Our take —

This article describes viral shedding among “asymptomatic” cases on the Diamond Princess cruise ship, where asymptomatic was defined as developing neither fever nor respiratory symptoms rather than no symptoms at all. The median number of days between the first positive PCR test and two negative PCR tests was nine days, with older cases shedding the virus for longer than younger cases. Given the definition of asymptomatic used in this letter to the editor, it is uncertain if the findings can be generalized to truly asymptomatically infected people.

Study design


Study population and setting

This is a letter to the editor describing the natural history of passengers and crew members from the Diamond Princess who were infected with SARS-CoV-2 but had no fever or respiratory symptoms. Authors considered these infections to be “asymptomatic”. Passengers and crew members gave multiple samples after their diagnoses for polymerase-chain-reaction (PCR) tests to check for the continued presence of virus.

Summary of Main Findings

Authors reported findings from 90 asymptomatic cases infected with SARS-CoV-2 from the cruise ship (58 passengers and 32 crew members), who were a median age of 59.5 years (interquartile range [IQR]: 36, 68). The median time between a case’s first PCR positive test for SARS-CoV-2 and two PCR negative tests was nine days (IQR: 6,11). In other words, for fifty percent of patients, the virus stopped being directly detectable in their biological samples within nine days after first testing positive via PCR. Ninety percent of cases were negative by 15 days. Viral RNA in biological samples from cases was detectable for longer among older versus younger adults. For example, the median time for a 68 year old case was 4.41 days (95% confidence interval: 2.28, 6.53) longer than a 36 year old case.

Study Strengths

This letter reports useful information regarding the duration of viral RNA shedding by PCR testing among cases who never developed fever and respiratory symptoms.


Although the title of this letter is “A Natural History of Asymptomatic SARS-CoV-2 Infection”, a major limitation is that cases were considered asymptomatic if they did not develop a fever or respiratory symptoms. However, a case is usually only considered asymptomatic if they are infected with SARS-CoV-2 but never develop any symptoms or disease (i.e., coronavirus disease (COVID-19)). It is possible that some infections reported in the letter could have had symptoms besides fever or respiratory ailments. Therefore, these estimates of viral shedding may not provide an accurate depiction of the natural history of SARS-CoV-2 among truly asymptomatic cases.

Value added

This is one of the first articles aiming to demonstrate the natural history of infection among cases without fever or respiratory symptoms.

This review was posted on: 4 July 2020