Low humidity increases COVID-19 risk: Another reason to wear a mask
Dry air could prompt further disease spread

Date:
August 18, 2020
Source:
University of Sydney
Summary:
A new study from Australia confirms a link between COVID-19 cases
and lower humidity.



FULL STORY ==========================================================================
A study focused on the Greater Sydney area during the early epidemic
stage of COVID-19 found an association between lower humidity and an
increase in community transmission.


==========================================================================
Now a second study by the same team confirms the risk.

The study is published today in Transboundary and Emerging Diseases.

The research led by Professor Michael Ward, an epidemiologist in the
Sydney School of Veterinary Science at the University of Sydney, and
two researchers from our partner institution Fudan University School of
Public Health in Shanghai, China, is the second peer-reviewed study of
a relationship between weather conditions and COVID-19 in Australia.

"This second study adds to a growing body of evidence that humidity is
a key factor in the spread of COVID-19," Professor Ward said.

Lower humidity can be defined as "dryer air." The study estimated that
for a 1 percent decrease in relative humidity, COVID-19 cases might
increase by 7- 8 percent.



==========================================================================
The estimate is about a 2-fold increase in COVID-19 notifications for
a 10 percent drop in relative humidity.

"Dry air appears to favour the spread of COVID-19, meaning time and place become important," he said. "Accumulating evidence shows that climate
is a factor in COVID-19 spread, raising the prospect of seasonal disease outbreaks." Why humidity matters Professor Ward said there are biological reasons why humidity matters in transmission of airborne viruses.

"When the humidity is lower, the air is drier and it makes the aerosols smaller," he said, adding that aerosols are smaller than droplets. "When
you sneeze and cough those smaller infectious aerosols can stay suspended
in the air for longer. That increases the exposure for other people. When
the air is humid and the aerosols are larger and heavier, they fall and
hit surfaces quicker.

"This suggests the need for people to wear a mask, both to prevent
infectious aerosols escaping into the air in the case of an infectious individual, and exposure to infectious aerosols in the case of an
uninfected individual," Professor Ward said.

Key findings:
* Additional evidence from the Sydney COVID-19 epidemic has confirmed
cases
to be associated with humidity
* Reduced humidity was found in several different regions of Sydney
to be
consistently linked to increased cases
* The same link was not found for other weather factors -- rainfall,
temperature or wind
* Climatic conditions conducive to the spread of COVID-19 present a
challenge to public health.

Further research Further studies on humidity for the remainder of the
year are needed to determine how the humidity relationship works and
the extent to which it drives COVID-19 case notification rates.


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


========================================================================== Journal References:
1. Michael P. Ward, Shuang Xiao, Zhijie Zhang. Humidity is a consistent
climatic factor contributing to SARS‐CoV‐2 transmission.

Transboundary and Emerging Diseases, 2020; DOI: 10.1111/tbed.13766
2. Michael P. Ward, Shuang Xiao, Zhijie Zhang. The role of climate
during
the COVID‐19 epidemic in New South Wales,
Australia. Transboundary and Emerging Diseases, 2020; DOI:
10.1111/tbed.13631 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200818094028.htm

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