Biological Characteristics and Transmission
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has weak
resistance. It can be inactivated by 56 ℃ for 30 minutes, 75% ethanol,
chlorine containing disinfectant and peracetic acid1.
SARS‐CoV‐2 spike protein uses the SARS‐coronavirus receptor, and binds
angiotensin-converting enzyme 2 (ACE‐2) for entry host cells. The
SARS‐CoV‐2 belongs to the subgenus sarbecovirus, and has 96.2% homology
with bat coronavirus. The current view is that COVID-19 was introduced
into humans through an unidentified intermediary animal.
Human to human transmission occurs mainly through the spread of
respiratory droplets up to 2 meters, and may cause infection through
contact on the contaminated surface. The virus is also found in fecal
samples of patients, indicating that there may be a fecal oral
transmission pathway; however, this route requires further
investigation2. Epidemiological records in China
suggest that up to 85% of human-to-human transmission has occurred in
family clusters, with an absence of major nosocomial
outbreaks3. Pre symptomatic infectiousness is a
concern and many countries are now using 1–2 days of symptom onset as
the start day for contact identification4.
Maternal-infant vertical transmission is questionable. A recent study
showed no evidence of intrauterine infection of COVID-19 caused by
vertical transmission from mothers who developed COVID-19 pneumonia in
their third trimesters. The samples of amniotic fluid, cord blood,
newborn throat swab and breast milk of 9 patients were analyzed, and 6
of them were negative for SARS-COV-25. But previous
studies have shown the possibility of materno-fetal transmission of
human coronavirus (HCoV) with evidence of the virus exists not only in
maternal respiratory swabs, but also in vaginal
swabs6.