tetano
Editor, Senior Moderator
Emerg Infect Dis
. 2021 Oct 12;28(1).
doi: 10.3201/eid2801.211591. Online ahead of print.
Mask Effectiveness for Preventing Secondary Cases of COVID-19, Johnson County, Iowa, USA
Jacob Riley, Jamie M Huntley, Jennifer A Miller, Amelia L B Slaichert, Grant D Brown
Abstract
In September of 2020, the Iowa Department of Public Health released guidance stating that persons exposed to someone with coronavirus disease (COVID-19) need not quarantine if the case-patient and the contact wore face masks at the time of exposure. This guidance differed from that issued by the Centers for Disease Control and Prevention. To determine the best action, we matched exposure information from COVID-19 case investigations with reported test results and calculated the secondary attack rates (SARs) after masked and unmasked exposures. Mask use by both parties reduced the SAR by half, from 25.6% to 12.5%. Longer exposure duration significantly increased SARs. Masks significantly reduced virus transmission when worn by both the case-patient and the contact, but SARs for each group were higher than anticipated. This finding suggests that quarantine after COVID-19 exposure is beneficial even if parties wore masks.
Keywords: 2019 novel coronavirus disease; COVID-19; Iowa; SARS-CoV-2; USA; contact tracing; coronavirus disease; masks; public health; quarantine; respiratory infections; secondary attack rate; severe acute respiratory syndrome coronavirus 2; viruses; zoonoses.
. 2021 Oct 12;28(1).
doi: 10.3201/eid2801.211591. Online ahead of print.
Mask Effectiveness for Preventing Secondary Cases of COVID-19, Johnson County, Iowa, USA
Jacob Riley, Jamie M Huntley, Jennifer A Miller, Amelia L B Slaichert, Grant D Brown
- PMID: 34637377
- DOI: 10.3201/eid2801.211591
Abstract
In September of 2020, the Iowa Department of Public Health released guidance stating that persons exposed to someone with coronavirus disease (COVID-19) need not quarantine if the case-patient and the contact wore face masks at the time of exposure. This guidance differed from that issued by the Centers for Disease Control and Prevention. To determine the best action, we matched exposure information from COVID-19 case investigations with reported test results and calculated the secondary attack rates (SARs) after masked and unmasked exposures. Mask use by both parties reduced the SAR by half, from 25.6% to 12.5%. Longer exposure duration significantly increased SARs. Masks significantly reduced virus transmission when worn by both the case-patient and the contact, but SARs for each group were higher than anticipated. This finding suggests that quarantine after COVID-19 exposure is beneficial even if parties wore masks.
Keywords: 2019 novel coronavirus disease; COVID-19; Iowa; SARS-CoV-2; USA; contact tracing; coronavirus disease; masks; public health; quarantine; respiratory infections; secondary attack rate; severe acute respiratory syndrome coronavirus 2; viruses; zoonoses.