Is fecal-oral transmission possible?
In several studies in pediatric and adult populations, the fecal
elimination of SARS-CoV-2 was found to be prolonged for several weeks,
which has led to speculating a possible fecal-oral
transmission.14,15 The fecal-oral transmission route
has also been previously demonstrated for other coronaviruses, such as
MERS-CoV. However, it has been argued that the positivity of reverse
transcriptase-polymerase chain reaction (RT-PCR) for SARS-CoV-2 on
rectal swab or stool does not imply that it is vital and able to infect
other subjects. A study by Wang et al. including 205 patients with
SARS-CoV-2 infection (more than one thousand samples from blood, sputum,
feces, urine, nasal swab, and other biological samples) is particularly
noteworthy.16 Fecal samples were positive in 29% of
cases; moreover, four samples revealed a vital virus after culture,
possibly transmitting the infection.
In adults, RT-PCR positivity on stool samples in patients diagnosed with
COVID-19 varies between 6 and 53.4% across studies. It is interesting
that in some case-series, around 20% of the fecal samples resulted
positive even after that RT-PCR on pharyngeal swab had turned
negative.15 Therefore, a fecal-oral transmission might
also be possible in asymptomatic or convalescent patients.
Similar findings have been observed in children. In a Chinese study, 8
out of 10 children were still positive for RT-PCR on the rectal swab for
a few days after RT-PCR negativization on nasopharyngeal
swabs.16 Some authors suggested that serial rectal
swabs should be performed over time before declaring the child
non-infectious. In a recent case series, including 22 children with
documented SARS-CoV-2 infection, fecal RNA shedding was observed in 68%
of patients independently from gastrointestinal symptoms. The estimated
positivity on day 14 from symptom onset was 52% for a nasopharyngeal
swab and 31% for stool swab.17 In another Italian
study, two pediatric cases with RT-PCR positivity on stool were
reported. The pediatric literature available at publication date was
reviewed, including overall 13 children affected by SARS-CoV2 infection
with a positive RT-PCT on the stool and/or rectal
swab.9 Authors suggest that negativity in both
nasopharyngeal and stool samples might be a standard requirement for the
cessation of mandatory isolation.