Age trend
A survey report on the epidemiological characteristics of COVID-19 cases
from January 21 to February 20, 2020 in Zhejiang
Province,China,
indicated that in 108 asymptomatic cases, patients <30 years old
accounted for 28.70%, higher than the ratio of the confirmed
cases(13.86%)[6] .Another investigation of imported cases from
March 1 to April 7 from the same place showed that 43 cases were
asymptomatic carriers in total 91 cases reported(47.25%), and the
proportion of patients < 30 years old in asymptomatic cases was
51.16%, while it was 33.33% in the confirmed cases [7]. In Hunan
province, China, the median ages of the confirmed cases and asymptomatic
carriers of COVID-19 reported were 44 and 35 years respectively, and the
proportion of young patients
aged
3-18 years was proved to be relatively higher in asymptomatic cases (
χ2= 65.52, P<0.01)[8]. From January 21 to
February 29, there were 14 cases of asymptomatic COVID-19 infection in
Yangzhou, Jiangsu province, China, the majority of them were young
adults, 85.7% of them were under 50 years old and the average age was
38.7 years[9].
Although some of the sample size was relatively small, the surveys were
all from provinces located close to Hubei where the outbreak first
started and the epidemic was severe, so we believed the results have
some underestimated value. Moreover, We have
reviewed literatures
on family aggregation epidemic and list the asymptomatic carriers or
close contacts
without infection(no clinical symptoms and negative nucleic acid
test), and found that women and children make up the majority of these
cases(13/16 , 81.25%)(Table 1.)[10-21]. It is interesting that
the six uninfected
close contacts
cases were all young females or
children, none was adult male,
though our sample size is very small(Table 1.). Several researches have
showed that children are not susceptible to
SARS-CoV-2 infection compared with the adults[22, 23], which still
needs a large-scale epidemiological investigation to confirm it. We will
talk about the children asymptomatic cases in this article later.