New study gives insight into how often COVID-19 spreads through
households

Date:
August 25, 2021
Source:
University of North Carolina Health Care
Summary:
A new study demonstrates how quickly COVID-19 can spread through
a household, and provides insight into how and why communities of
color have suffered disproportionately from the pandemic.



FULL STORY ==========================================================================
A new study out in the Clinical Infectious Diseases journal demonstrates
how quickly COVID-19 can spread through a household, and provides insight
into how and why communities of color have suffered disproportionately
from the pandemic.


==========================================================================
The observational study, conducted between April and October of 2020,
followed 100 COVID-positive patients around the Raleigh, NC area and
included a total of 208 additional household members. A household member
was defined as someone who was staying in the same living space as the
person who tested positive.

Researchers tested other household members with PCR nasal swabs weekly
for three weeks following the initial COVID case, or by a seroconversion antibody test at the fourth week. Excluding 73 household members who
already tested positive for COVID when researchers got to their home,
the secondary attack rate among household contacts was 32 percent.

"We think this number is actually much higher," said Jessica Lin, MD,
the study's senior author and assistant professor in the UNC Department of Medicine, Division of Infectious Diseases at the UNC School of Medicine.

"Sometimes we were getting to households to test people four or five
days after the initial COVID-positive person showed symptoms. By that
time a lot of household members were already infected. But because
that infection happened before we got there, we couldn't include it in
our data." This study also took place before the more infectious Delta
variant was widely circulating in the U.S., leading Lin to believe the
current secondary attack rate in households is significantly higher.

The majority of secondary cases occurred within the first week of the
initial positive COVID test. Researchers found that these secondary
cases shared a similar nasopharyngeal viral load, or the amount of virus
a person had in their nose and throat.

"This means the viral load of the index case matters," Lin said. "A
higher viral load means it's more likely that there will be secondary transmission in a household, and viral load is also an indication of
how sick a person could get from the virus." The study also looked at
living density -- the concentration of people living within a household
-- as a factor that determined whether COVID spread to other household
members. Of the participants enrolled in the study, 44 percent identified
as Hispanic or non-white. Researchers found that minority households were
more likely to experience a higher living density, and had a higher risk
of secondary infection that white households.

"It's very difficult to follow public health guidelines in some living situations," Lin said. "If you have multiple people and generations
sharing common areas or bedrooms, or say you are a single parent, it
becomes nearly impossible to isolate or even physical distance." Lin says these findings all come back to one key message -- vaccinations. The more people in a household that are vaccinated, the less likely the chance
that secondary COVID infections occur. Even if one person is vaccinated,
it helps, especially if the vaccinated person happens to be the first
infection in a household. A person who has been vaccinated will most
likely have a lower viral load, which will make it harder for the virus
to infect other household members.

"Household transmission really is the main place where most people are
getting COVID," Lin said. "It's spreading from their family and friends,
people that are in their bubble and they feel safe with. When you get vaccinated, you aren't just protecting yourself, you're protecting those important people around you." This study was funded by the UNC COVID-19 Response Fund, the North Carolina Translational and Clinical Sciences
Institute (NC TraCS), and a UNC Gillings Innovation Lab Award.

========================================================================== Story Source: Materials provided by
University_of_North_Carolina_Health_Care. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Carla Cerami, Zachary R Popkin-Hall, Tyler Rapp, Kathleen Tompkins,
Haoming Zhang, Meredith S Muller, Christopher Basham, Maureen
Whittelsey, Srijana B Chhetri, Judy Smith, Christy Litel, Kelly D
Lin, Mehal Churiwal, Salman Khan, Rebecca Rubinstein, Faith Claman,
Katie Mollan, David Wohl, Lakshmanane Premkumar, Kimberly A Powers,
Jonathan J Juliano, Feng-Chang Lin, Jessica T Lin. Household
transmission of SARS-CoV-2 in the United States: living density,
viral load, and disproportionate impact on communities of
color. Clinical Infectious Diseases, 2021; DOI: 10.1093/cid/ciab701 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210825153752.htm

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