Coronavirus is starting to look more and more like the T-1000 from Terminator 2: Just when you think you’ve smashed it and it’s now a puddle on the ground, it starts re-forming and coming back more determined than ever:

The coronavirus may be “reactivating” in people who have been cured of the illness, according to Korea’s Centers for Disease Control and Prevention.

About 51 patients classed as having been cured in South Korea have tested positive again, the CDC said in a briefing on Monday. Rather than being infected again, the virus may have been reactivated in these people, given they tested positive again shortly after being released from quarantine, said Jeong Eun-kyeong, director-general of the Korean CDC.

“While we are putting more weight on reactivation as the possible cause, we are conducting a comprehensive study on this,” Jeong said.

The fact that this is from South Korea makes it slightly more worrying than it already is. The Koreans have, by international acclamation, been awarded the title of “country that has handled the coronavirus better than anyone”, testing nearly everyone and everything they can lay their hands on. By and large, they’ve been at the forefront of the science, and most of the present response in Ireland and elsewhere is modelled on the very successful approach Seoul has taken.

But if this is true, then we’re not ever going to get rid of Coronavirus, at least until there’s a vaccine:

Fear of re-infection in recovered patients is also growing in China, where the virus first emerged last December, after reports that some tested positive again — and even died from the disease — after supposedly recovering and leaving hospital. There’s little understanding of why this happens, although some believe that the problem may lie in inconsistencies in test results.

Epidemiologists around the world are in a race to find out more about the virus that causes Covid-19. The pathogen’s rapid global spread has recently seen the focus shift to patients who contract the virus but display few or atypical symptoms. Korea has been at the forefront of tracking these cases, which are causing particular concern in China, where the epidemic is showing signs of coming under control.

To be fair, there are a couple of potential explanations for re-activation of the virus that might be relatively innocent.

For starters, in people with compromised immune systems, immunity to it simply might not build up as a result of being infected. You could be cured by medicine, and by having a mild dose to begin with, but you never develop the immunity a person with a normal immune system does, and therefore you can get it again.

Second, testing is apparently an inexact science:

False positives are bad, but the damage from a false positive is minimal. You’re told that you have the disease even though you don’t, so you quarantine yourself. Two or three weeks later, you reemerge. That’s costly in terms of productivity but you’re not spreading any viruses that way.

A false negative, where you’re told that you don’t have the disease even though you do, is a different matter. The Wall Street Journal cites a specific case in this story of a mom in Texas who came down with a fever and cough, isolated herself in the family home, then tested negative. So she began mixing with her family again. Now her daughter has aches and fatigue.

There’s a Wall Street Journal story here (behind a paywall, alas, unless you have a subscription) from last week that suggests that the Americans are finding that one in three tests returns a false result – either a false negative, or a false positive.

So, if that’s right, then it could be as simple as the Koreans letting people back out onto the street who had received the all-clear but who actually still had the virus, so when it flared back up, their cases were recorded as re-infections, but in reality they’d simply never been cured to begin with.

So that’s the positive take. But the other possibility is that the virus never really goes away, once you have it, and that it simply lies dormant waiting to flare up again, like HIV or other auto-immune diseases.

In that case, not getting it in the first place becomes even more imperative.

The scary thing, of course, is that this is being debated by scientists in the first place. Because when they’re debating something, that means they don’t know what the truth is. Let’s hope it’s just bad testing. Because the alternative makes the present crisis a lot longer lasting than it already is going to be.