Researchers examined all 243 coronavirus cases that were reported in Singapore from Jan. 23 to March 16. They identified seven clusters of cases where presymptomatic transmission most likely occurred.
The seven clusters occurred between Jan. 19 and March 12 and involved from two to five patients each, according to the report. Ten of the cases within the clusters could be attributed to presymptomatic transmission, and accounted for 6.4% of the 157 locally acquired cases reported as of March 16, researchers added.
“The possibility of presymptomatic transmission of [the coronavirus] increases the challenges of COVID-19 containment measures, which are predicated on early detection and isolation of symptomatic persons,” researchers said in their findings. “The magnitude of this impact is dependent upon the extent and duration of transmissibility while a patient is presymptomatic, which, to date, have not been clearly established.”
Researchers said that in four of the clusters, they determined transmission exposure occurred one to three days before the source patient developed symptoms.
The study had three limitations, researchers said. There’s the possibility of an unknown source transmitting the virus to the clusters, recall bias could affect the accuracy of symptom onset dates, and under-detection of asymptomatic cases is possible, researchers said.
New York City joined Los Angeles in recommending the general public wear face coverings, which officials initially said was not necessary in order to maintain supply for health-care workers. President Donald Trump and Vice President Mike Pence also said Thursday night that the CDC will issue new nationwide guidance “in the next several days” about wearing masks to prevent the spread of COVID-19.
Source Article from https://www.cnbc.com/2020/04/03/heres-the-study-behind-why-nycs-mayor-now-recommends-masks-in-public.html
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