  We measure the effect of different public health regulations to the spread of
COVID-19, based on a SEIRA model -- a SEIR model including asymptomatic
transmissions. The cumulative confirmed cases and death show nonlinear positive
relationship with the value of asymptomatic rate. Based on this model, we
analyze the inhibit effects to COVID-19 of three types of public health
policies, i.e. isolation of laboratory confirmed cases, general personal
protection and quarantine (lock-down). The simulations conclude that the
isolation display limited effects to the asymptomatic viral carriers. The
general personal protection and quarantine perform similar effects when the
their percentages of participants are same. When the total proportion of
asymptomatic, mild symptomatic and neglected patients is 40%, only depends on
isolation policy may lead to an additional 75% infections, compared with
general personal protection or quarantine with an efficiency 80%. At end, we
provide seven recommendations of public health intervention before and during
an aerial transmitted epidemic (COVID-19).
