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Nearly 50 Covid-19 cases have now been reported across greater Sydney outside the northern beaches; a third of the 146 community transmission cases reported in New South Wales this month. Most, but not all, have been linked to northern beaches cases or venues. It is the “but not all” that really matters here, even more than the number of cases. If you can’t link all cases back to a known case, or at least a venue where an exposure event is known to have occurred, it’s a warning sign that you have unidentified cases out there in the community.
When thorough forensic case investigations – which NSW Health is now very experienced in – fail to identify transmission chains, it means there are cases out there who didn’t get tested, either ignoring their symptoms or who did not have symptoms. There are also those people’s other close contacts who may still be incubating the virus or may be infectious themselves and passing the virus on unknowingly.
This is the time to mandate masks in shared public spaces where you cannot keep your distance, or any enclosed spaces when with people outside your household. Masks won’t stop you being exposed if you are unlucky enough to be at a venue where a case is present, but they will reduce your chances of developing an infection – while you may still need to go into quarantine for 14 days, at least all your close contacts won’t have to go through that too if you test negative as you start isolation.
Consistent mask wearing actually makes it easier for health authorities to take those decisions that keep businesses and venues open in the face of known community transmission. It’s part of the essential partnership between the public, businesses and the public health response.
Covid-safe compliance is another essential component, whether it’s record keeping and density compliance in a pub, or individuals remembering to hand sanitise and keep their physical distance. Masks should be part of this, given the evidence they work – they made a measurable difference to transmission rates in Melbourne when introduced midway through the second wave.
NSW has demonstrated impressive community engagement in testing, hitting nearly 70,000 tests completed on Christmas Eve. However, the numbers have drifted down since and are now well below 20,000. Potential exposure sites are still being added to the alert list daily, and it’s incredibly important that people keep an eye on this and seek testing if at one of these venues in the given time frame, and stay isolated until they get the result.
The risk in the efficiency of the NSW Health venue notifications and the early public engagement is that infected people might be getting tested before they have enough viral load in the nose and throat to test positive. On average it takes five days from exposure to develop symptoms, but may be as little as one to two days before you are infectious and test positive. However, it can be much longer than that also, hence why we quarantine people for a full 14 days.
People who tested within the first few days of being at one of these exposure sites/times should also think about re-testing after day 11 as they may have still have been incubating the virus the first time around, or test even sooner if any symptoms appear.
Some measured easing of restrictions was put in place for Christmas across all areas in greater Sydney. That’s now one average incubation period ago, and so we expect to see cases linked to any gatherings an infectious person attended appear from now. We already see that with the six related cases in Sydney’s inner west, and with many more close contacts of this multiple household cluster in isolation.
Household settings are high risk for transmission. You do not want to bring the virus home. We hear a lot about superspreader events. These are dangerous as they accelerate case numbers by spreading the virus across many people at one time, but the main driver of the large case numbers that arise is that these primary contacts then take the virus home to many households. The people directly exposed at superspreader events are only a small proportion of the ultimate case number. Homes remain one of the highest risk locations for people to catch this virus.
Visitors to Sydney have also returned home to other states earlier in December. So far this does not seem to have triggered any local community transmission further afield, but as we do not know the actual timing or means of the arrival of this overseas variant into Sydney, it is still possible that there are undetected cases outside greater Sydney. We should all therefore be mindful of how we spend our New Year’s Eve. There’s a lot we all want to celebrate about this year being over, but the more carefully we all do that, the more likely it is that our new year will look a whole lot better than the last.
• Catherine Bennett is chair in epidemiology at Deakin University
Source: The Guardian
Keyword: A third of Sydney’s Covid outbreak is outside the northern beaches. It’s time to mandate masks | New South Wales