As waves of returning Singaporeans bring the coronavirus home with them, the last thing the stretched healthcare system needs is a new local cluster.
But on Wednesday night, worrying news surfaced that staff at a PAP Community Foundation (PCF) pre-school had been infected.
At least 15 staff have tested positive, plus another five family members. The country's largest pre-school operator has closed all its centres, not just to disinfect them, but to review operations.
Singapore's fight against the virus is at an inflection point, and whether it wins the battle could hinge on the number of local clusters to surface in the next few weeks.
If too many individuals and groups get infected here, the system will be overwhelmed. Even more drastic measures may ensue, such as closing schools and workplaces.
But if local spread can be contained, then resources can be funnelled towards the thousands of people coming back from high-risk countries such as Britain and the United States, and making sure that infections from this group do not erupt into clusters of their own.
After a few weeks - hopefully - imported cases will start to taper off, and the number of new cases each day will also begin to stabilise. That is when some of the current restrictions can be eased.
When a cluster forms, the knock-on effect on labour, and the cost to contain its spread, is tremendous.
Not only do patients have to be treated and monitored, and premises cleaned, others must get tested, contact tracing done, and people ordered to be under quarantine or on stay-home notice.
The numbers are telling: As of yesterday, over 400 people were still in hospital, with 18 requiring intensive care. Another 87 were in isolation. In addition, over 3,200 individuals remained under quarantine, with another 38,000 on stay-home notices.
In the case of PCF, the decision to close one centre for one day snowballed into the closure of 360 pre-school centres - affecting over 40,000 children - for four days, as more employees in the first centre were found to be sick.
Personal responsibility goes a long way towards taming these numbers.
This includes practising good hygiene, not going out if you do not have to, and seeing the doctor and staying at home if unwell.
Indeed, the pre-school cluster is one which may have been minimised, or may not even have materialised, if staff had not been at work when they felt sick.
Employers must reinforce this message with their workers. For this period, they could also waive the need for a medical certificate for staff to call in sick.
The authorities, in efforts to contain the spread of the virus, have tightened border controls and imposed travel restrictions, pulled the plug on most group entertainment and activities, and indicated that they will come down hard on those who flout the rules.
Yet, there are still people on stay-home notices sneaking out for meals or inviting friends home, and others who lie about where they have been, doctor-hop, gather in large groups or go out when ill.
All it takes is for one thoughtless action to negate the best rules and guidelines, and derail the efforts of the thousands of medical, security, cleaning and other front-line staff working flat out to cope.
It is not always easy to decide if you are really sick. If in doubt, stay home.
Changing the way we think, and thinking things through, will go a long way towards protecting ourselves, our loved ones and the people around us.
And that is how the war against the virus may be won.
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