SINGAPORE - As if the coronavirus causing havoc the world over needed any more unknowns.
Epidemiologists who have been piecing together how fast it is spreading, and how lethal it is, will be scratching their heads again - because the definition of the disease itself has changed.
When it comes to taking stock of the toll the new virus is taking, all eyes have been on China, because that is where the vast majority of cases and deaths are happening.
But China has a new way of deciding who is infected.
It has revised the way cases are confirmed in Hubei province, the region hardest-hit by the virus, by broadening the scope of diagnoses.
Previously, only infections confirmed by specialised testing kits were considered accurate. This is the gold standard globally.
Now, instead of relying only on laboratory tests, cases in Hubei can be flagged through clinical diagnosis by doctors.
So a patient can be confirmed to be suffering from Covid-19, as the disease is now called, if they exhibit symptoms of severe respiratory tract disease and a CT scan shows lesions in their lungs.
And just like that, just as hopes glimmered that the nation could be turning the corner in its battle against the coronavirus, all bets are off.
Earlier this week, some experts were feeling positive.
Leading epidemiologist Zhong Nanshan told Reuters that, based on modelling, recent developments and government action, the situation in some provinces was already improving, with the number of new cases declining.
Then when the new classification system kicked in, China reported a sharp spike in infections and deaths overnight, with infections increasing by about 15,000.
But it is virtually impossible now to tell what is due to the broader new definition, and how much is due to the waxing or waning of the virus.
No doubt, there is good reason for the new measures.
With test kits in short supply, Hubei health authorities said the new methodology will allow patients to receive treatment as soon as possible, and in a specialised ward in a hospital, instead of waiting in a quarantine centre or at home for lab results.
But there is also no good reason for Singapore to follow suit.
Indeed, the new accounting method will have no bearing on how the country tallies its own coronavirus patients, which remains the same.
Whether or not a patient is defined as a confirmed case here hinges on laboratory tests.
The authorities have made clear that Singapore has enough diagnostic tests available for any suspected case.
Such tests are critical during the earlier stages of the outbreak, which the country is experiencing, say doctors and scientists here.
This is because Singapore is still at a point where isolation, quarantine, contact tracing and ring fencing could make a difference.
"We are still at an early stage - every case counts and needs to be tested," said one scientist.
"This is the right approach."
Also, with figures here still very low, having doctors rather than lab tests make the final diagnosis would end up including a lot of people who do not actually have the illness, which would waste resources and heighten panic.
Hours spent on contact tracing for such individuals would stretch manpower thin when personnel could be better spent dealing with real patients, for instance.
So it is crucial to make sure that every confirmed cases is indeed one.
Agreeing, another doctor stressed that instead of finding more cases that may have slipped through the net, the new approach would merely create too many false positives.
In addition, those infected but with no symptoms would slip under the radar.
"We should follow science," he said.