Cases of coronavirus could rise to a peak in May or June, according to the "best guess" of Wales' chief medical officer.
A total of 450 people have been tested for coronavirus in Wales so far, with just one case confirmed in Swansea.
Dr Frank Atherton said there was "active surveillance in place" of patients coming through intensive care or seeing their GP.
He was giving details of the Welsh response to the outbreak of the virus.
More than 90,000 people around the world have been infected, with more than 3,000 deaths.
An adult from Swansea is being treated at the Royal Free Hospital in London after contracting the virus in northern Italy.
Public Health Wales said it had been in touch with the patient's "close contacts" and appropriate action was being taken to reduce any risk to public health.
The UK government said on Tuesday up to one in five workers could be off sick with the virus at the same time at the peak of a coronavirus epidemic.
Its preparation plans said:
- Police may focus on only responding to the most serious crimes and maintaining public order
- The military could provide support to emergency services
- Non-urgent hospital care may be delayed to focus on coronavirus patients and retired doctors and nurses may be recalled
- Other measures included school closures, reducing social gatherings and working from home
- Councils in Wales have the powers to apply to magistrates for an order to "isolate, detain or require" individuals to undertake a medical examination.
However, Dr Atherton said now was a time for a "period of calm preparation" with a "mantra" of personal hygiene and looking at social contact.
There are currently no plans to close schools and decisions to do so would only be taken with the scientific evidence to back it up.
He outlined what would happen during different phases of the outbreak, potentially involving a pandemic.
His "best guess" was cases would escalate and said modelling suggested this would happen from April, followed by six to eight weeks of a significant increase with a peak towards May and June, before a downturn.
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There is a scenario which could see NHS operations cancelled and outpatient clinics stopped, but health boards have plans in place in case this happened.
If there was a "significant number" of patients, this could see people treated in isolation facilities.
Most cases were likely to be mild but there was a significant risk the NHS would have to treat more patients.
Plans are also being made to cover increased NHS staff absence, including increasing capacity in hospitals and treating people in their own homes.
Dr Atherton said people who had a cold should not visit an elderly relative in a care home, for example, to "help protect the most vulnerable".
Wales' Health Minister Vaughan Gething said the immediate focus was on containment and delaying the spread.
How are businesses coping?
Neil Gregory, director of GOS Tools Engineering, in Blaenavon, Blaenau Gwent, said the disease had already had an impact and fears it could get worse.
"We had visitors due this week from South Korea. Unfortunately, those plans were cancelled.
"We have six staff going to Austria on a training course in two or three weeks but their flights have been cancelled.
"I think in the short term we don't know. The key is not to panic, take the advice available and protect our employees the best we can.
"I think the real, genuine worry to Welsh business is we don't know - particularly if production slows down in Korea or China. That would have an impact on a lot of Welsh businesses."
The NHS 111 line was now available across Wales for coronavirus advice and support, he said.
Previously, the number had only been available to callers from Hywel Dda, Powys, Aneurin Bevan and Swansea Bay health board areas and callers from other areas had been told to use the NHS Direct number, 0845 46 47.
Why does Wales not have its own isolation unit?
Mr Gething said having four isolation units in England at this stage was a "deliberate choice" by all UK nations, agreed several weeks ago, in response to a global issue.
He said it was not about having a "fortress Wales approach" and he had been taking part in regular Cobra calls with fellow health ministers.
However, the message for today was "go about your normal business", he said, with "catch it, bin it, kill it" and hand washing being important to emphasise.