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A joint Australian-Chinese study released on Tuesday has linked lower humidity with higher rates of COVID-19 transmission.
Drier air across several different regions of Sydney has been consistently linked to higher numbers of COVID-19 infections, with similar links not true for other weather factors including rain, temperature and wind.
Published in the medical journal, Transboundary and Emerging Diseases, the study estimated that for a 1 percent drop in humidity, COVID-19 cases could increase by 7-8 percent, and for a 10 percent drop, infections could as much as double.
To conduct the research, epidemiologist Professor Michael Ward from the University of Sydney teamed up with Shuang Xiao and Zhijie Zhang from the partner institution Fudan University School of Public Health in Shanghai, China.
It is the second such study by the group regarding the relationship between weather conditions and COVID-19 in Australia, following a larger study conducted in China earlier in the year.
"The consistency between studies is increasing confidence that humidity is a key factor in the spread of COVID-19. Dry air appears to favor the spread of COVID-19, meaning time and place become important," Ward said.
According to Ward, the result raises the prospect of seasonal disease outbreaks, and greatly supports the use of face masks in order to prevent the spread.
He added that the result is not entirely unexpected considering that when humidity is lower, the air is drier and it makes aerosols smaller.
"When you sneeze and cough, those smaller infectious aerosols can stay suspended in the air for longer. That increases the exposure for other people," he explained.
"When the air is humid and the aerosols are larger and heavier, they fall and hit surfaces quicker."
The team said further research is required to draw more conclusive ties between humidity and virus transmission and expand on how that can be taken into account to shape the public health response.
