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High and dry: Why August could be the most dangerous month in Australia's fight against COVID-19 

The falling humidity levels in winter could lead to a spike in COVID-19 cases in Australia, experts have warned. 

Researchers at the University of Sydney found just a one per cent drop in humidity could boost the number of cases of the deadly virus by six per cent. 

The study's lead epidemiologist Michael Ward said data from almost 800 cases of COVID-19 in Australia - mostly in Sydney - showed lower humidity levels were linked to an increase in case notifications.

Professor Ward said humidity in the New South Wales capital was lowest in August, meaning the final winter month could be the most dangerous for the virus' spread.

Australians have been warned falling humidity levels could lead to a spike in coronavirus cases in winter Pictured: Masked people line up in the rain on Monday for retail vouchers distributed by the City of Melbourne to help international students impacted by COVID-19

He added there were clear biological reasons why humidity could affect the spread of the coronavirus.

'When the humidity is lower, the air is drier and it makes the aerosols smaller,' Professor Ward said.

'When you sneeze and cough those smaller infectious aerosols can stay suspended in the air for longer.'

Bureau of Meteorology data shows there is approximately a 10 per cent drop in average humidity in Sydney between January and August. 

The research was conducted alongside the University of Sydney's partner institution Fudan University in Shanghai, China. 

Professor Ward said though the study was limited to cases contracted in the summer months, primarily in Greater Sydney, so further research is needed to determine how humidity impacts COVID-19.

Two women wearing masks shield from the rain in Melbourne on May 9. The study's lead researcher said average humidity in Sydney was lowest in August

Professor Michael Ward said when humidity is lower, the air is drier - meaning when people sneeze and cough infectious particles can travel further

Pedestrians wearing coats and masks in Melbourne on May 9. Prior research has already established a link between transmission of COVID-19 and relative humidity levels

Previous research has identified a link between climate and occurrence of SARS-CoV cases in Hong Kong and China, and MERS-CoV cases in Saudi Arabia.

A recent study on the COVID-19 outbreak in China found an association between transmission and daily temperature and relative humidity, the team said in a statement.

CORONAVIRUS CASES IN AUSTRALIA: 7,228

New South Wales: 3,104

Victoria: 1,670

Queensland: 1,059

Western Australia: 591

South Australia: 440

Tasmania: 228

Australian Capital Territory: 107

Northern Territory: 29

TOTAL CASES: 7,228

RECOVERED: 6,625

DEATHS: 102

'The pandemic in China, Europe and North America happened in winter so we were interested to see if the association between COVID-19 cases and climate was different in Australia in late summer and early autumn,' Professor Ward said.

'When it comes to climate, we found that lower humidity is the main driver here, rather than colder temperatures. It means we may see an increased risk in winter here, when we have a drop in humidity.'

Experts have also warned of a possible resurgence of the deadly virus each year.

'The most likely time for it to recur is in winter,' Westmead Institute's Centre for Virus Research director Professor Tony Cunningham wrote.

'We don't know, but these are all things we have to be wary of.' 

However, the report also stresses that human behaviour is a dominant contributor to the transmission of coronavirus and social distancing has more impact in controlling the outbreak than a change in seasons.  

'It's something to be concerned about but not something to be worried about. [It's] something to be managed,' Dr Finkel wrote.

'It appears that in Australia, public policy will play a more dominant role than the arrival of winter on the viability and virulence of the SARS-CoV-2 virus.'

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