There is a claim from a doctor in Italy that the Covid-19 coronavirus may be losing potency in Italy. But like most horror movies have probably taught you, don’t make any assumptions that a threat has subsided until you are really, positively, absolutely sure that it has.

This Reuters video covers this claim by Dr. Alberto Zangrillo, who is head of the San Raffaele Hospital in Milan, Italy:

As a Reuters report indicated, Zangrillo said that “in reality, the virus clinically no longer exists in Italy,” and that “the swabs that were performed over the last 10 days showed a viral load in quantitative terms that was absolutely infinitesimal compared to the ones carried out a month or two months ago.” Hmm, “clinically no longer exists,” is a pretty bold claim. Did he check everyone in Italy for symptoms or the virus to confirm this statement? That would require a lot of swabs.

The WHO’s response to Zangrillo’s comments was akin to saying “what?” Just listen to what Mike Ryan, MD, MPH, Executive Director of the World Health Organization’s (WHO’s) Health Emergencies Programme said in a press conference today:

As you can see, Ryan warned that “we need to be exceptionally careful that we are not creating a sense that all of a sudden the virus has decided to be less pathogenic. That is not the case at all.” He emphasized that the Covid-19 coronavirus is still a “killer virus.”

As Kate Kelland and Emilio Parodi reported for Reuters, WHO Technical Lead and epidemiologist Maria Van Kerkhove said, “In terms of transmissibility, that has not changed, in terms of severity, that has not changed.”

Viruses like the Covid-19 coronavirus aren’t like Viagra. They don’t just automatically lose potency over time. Yes, there is the possibility that less dangerous versions of the virus could emerge and eventually become more prevalent than the initial version. There is also the “uh-oh” possibility that more dangerous versions may emerge. Both of these possibilities don’t tend to happen overnight, though.

Could moving closer to the Summer potentially lead to decreased virus activity? Sure, if transmission of the Covid-19 coronavirus shows the same type of seasonal fluctuation as the flu virus does. I covered this possibility previously for Forbes. It’s still not clear if this will be the case. Nonetheless, before making any bold statements about the virus losing potency, as they say with science and whisky, you’ve got to have enough proof.

That type of proof only comes after extensive testing and surveillance over time and over many locations. Testing in one hospital or even several hospitals over a ten day period is not going to tell you the whole story. That would be like going to a Pizza Hut and using your visit there to make conclusions about pizza in general. Remember not all pizza has cheese stuffed into its crust. Similarly, the amount of virus in testing swabs in a hospital or even a group of hospitals does not necessarily represent what is happening throughout the country.

Instead, you’ve got to get a broad enough sample over an extended period of time to really understand what’s happening across the country and make sure that it’s not just a momentary dip. An extended period of time means more than 10 days, which is still less than what may be the incubation period for the virus. For example, what if the virus is spreading more among disadvantaged or more socially isolated people who may not have ready access to health care and thus won’t necessarily be seen by doctors?

Also, keep in mind that Italy did shut things down for a while with aggressive social distancing measures. So all of those efforts probably decreased transmission of the virus for at least a bit. Will the re-opening of society in Italy lead to a bad sequel to what was a bad first installment, sort of like the movie Grown Ups 2 after the first Grown Ups movie? Could the sequel come in the Fall? It’s still too early to tell.

The situation in Italy does bear watching. More concrete and peer-reviewed scientific evidence is needed before concluding anything about new about the potency of the virus. Even if some change were to happen in Italy, that doesn’t necessarily mean that the same will apply elsewhere. What happens in Italy could just stay in Italy.