Thousands of Sydneysiders are urged to monitor for coronavirus symptoms after it was found lurking in sewage in NINETEEN suburbs

A coronavirus alert has been issued for Sydney's north-western suburbs after virus fragments were found in the sewage drained from 19 suburbs in the area.

NSW Health issued an urgent alert on Sunday afternoon calling on people in the Rouse Hill area to get tested after the state's monitoring system found virus fragments in sewage from a catchment area that services about 120,000 people.       

The area affected stretches from Castle Hill, Kellyville and Quakers Hill to Glenwood and Bella Vista.

NSW Health is testing Sydney's sewage for evidence of coronavirus (stock image). An alert has been issued for 19 suburbs in Sydney's northwest

Pictured: Coronavirus testing at Bondi Beach, Sydney. NSW Health is urging people in Sydney's northwest, southwest and around Moss Vale in the Southern Highlands to get tested

'The positive sewage result can be due to shedding of the virus by someone who may have previously had the illness, with the virus 'shedding' through their system for up to six to eight weeks later,' NSW Health said in the alert.

'Symptoms like a runny nose or scratchy throat, cough, tiredness, fever or loss of taste or smell can all signal COVID-19.'

Anyone who is tested has to remain isolated until a negative result is given, NSW Health said.

NSW Health has been testing sewage to find coronavirus particles that reveal someone in the catchment area is infected.

NSW Health's alert issued on Twitter on Sunday afternoon

Roughly 80 per cent of Sydney's sewage is then pumped out at just three sites: off Bondi Beach, North Head (near Manly) and at Malabar. 

The news comes as New South Wales recorded no new cases of locally-transmitted coronavirus in the 24 hours to 8pm Saturday, and three new cases in overseas travellers who are in hotel quarantine.

19 SUBURBS AFFECTED

Quakers Hill, Castle Hill, Annangrove

Kellyville, Box Hill, Kenthurst,

 Glenhaven, The Ponds, Rouse Hill,

North Kellyville, Kellyville Ridge, 

Beaumont Hills, Stanhope Gardens, 

Baulkham Hills, Glenwood, Bella Vista, 

Parklea, Acacia Gardens, Norwest

TESTING CLINICS SET UP AT:

Bella Vista Clinical Labs Pathology Drive-through Clinic, 14 Lexington Drive, L1, Unit 104, Bella Vista 

Quakers Hill Drive-through Clinic, 6 Melrose Avenue, Quakers Hill 

Castle Hill Drive-through Clinic, Castle Hill Showground 

Blacktown Showground Douglass Hanly Moir Pathology Drive-through Clinic, Blacktown Showground Carpark 

For other nearby clinics, visit COVID-19 testing clinics or contact your GP.

The state's total is now 4273 of which 63 are active cases with one patient in intensive care.

New South Wales now has more active coronavirus cases than Victoria which has only four active cases, all of which are in Melbourne. 

Experts have said the virus could be eradicated if contact tracers continue to act quickly when new infections are confirmed. 

'Even if the virus is out there, it is more likely to die out than spread,' Catherine Bennett, the chair of epidemiology at Deakin University told the ABC. 

The state is also investigating the source of a recent outbreak at Moss Vale in the Southern Highlands.

NSW Health renewed its call for testing around Moss Vale, Mittagong and Bowral, and also in Sydney's southwest including in Leppington, Hoxton Park and Prestons. 

'The process of becoming infected and infecting others often occurs silently, invisibly, and inadvertently,' NSW Health boss Dr Michael Douglas said.

'Some who are infected with the virus may not be aware that they have the infection, where symptoms are mild or not present at all. To ensure we can continue to control the spread of the virus, it is most important to step forward for testing if there is any concern at all that you may have been exposed or may have symptoms.'

A recent COVID cluster in south-western Sydney highlighted the importance of businesses using QR codes so all patrons could be easily contacted. 

Worldwide the coronavirus pandemic passed 50.2 million cases on Sunday evening with the USA worst hit on 10.2 million infections, according to Worldometers statistics website.

Travel from Denmark to the UK has been banned as concerns grow over a mutation in the virus linked to minks.

It is not yet known whether the mutation is significant, whether it affects the virus's virulence or transmissability.