Now that the US Department of Energy has concluded the SARS-CoV-2 virus that spawned the COVID pandemic most likely came from a lab, focus is back on where pandemics come from and how best to prepare.

At the height of the H5N1 bird-flu scare back in 2006, there was a common expression among top flu experts I spoke with: “the back-door pandemic.”

While many here and around the world were so worried about a bird-flu virus that was killing millions of birds but very few people, others were predicting another virus would come in “the back door” when we were least expecting it and cause the next pandemic.

In other words, public-health experts had bad aim when it came to predicting which virus would infect us on a grand scale — and the unfortunate tendency to couple this misdirection with excessive fearmongering.

In fact, the pandemic that followed, namely 2009’s H1N1 swine flu, was mild. Though this swine flu infected more than 60 million people in America, it only killed around 12,000 here, a very low number by pandemic standards. It was not the back-door pandemic the hype had us fearing.

COVID was and is that pandemic. No one predicted it — indeed few scientists were talking about coronaviruses at all. SARS and MERS had alarmed public-health experts, but only briefly, and most of our attention remained on influenza.

And too few people were talking about the possibility of a lab leak despite ongoing manipulations of novel viruses.

Somehow COVID didn’t teach us our pandemic radar is faulty. Instead, scientists and journalists are using the ferocity of this pandemic to try to scare us that some specific bug (like H5N1) or other will cause the next one — and we are pandemic deniers if we don’t acknowledge this.

But the fact is we don’t know and should admit it.

Center for Infectious Disease Research and Policy chief Michael Osterholm is a top epidemiologist more levelheaded than most experts. He told me that though H5N1 has been spreading to more and more species, the number of human infections has declined over the past few years; it doesn’t appear to be improving its facility to pass human to human.

Peter Palese, Mt. Sinai School of Medicine chair of microbiology and one of the world’s top influenza experts, agreed that the chance of an imminent bird-flu pandemic is small. But we need to help ensure that by culling and vaccinating more and more birds while increasing our surveillance and stockpiling our own vaccines just in case.

I agree with both but feel strongly that fear is not our best approach.

This applies to norovirus too — the winter flu, which is highly contagious and has sparked recent outbreaks in America, the United Kingdom and elsewhere. But outbreaks are self-limited, and it has very low death rates, generally fewer than 800 per year. 

Norovirus will not be our next pandemic. There are many strains out there, but there are no sea changes.

The widely popular HBO show “The Last of Us,” which depicts a fungal pandemic devastating society, has contributed to concerns over fungal outbreaks.

But Dr. George Thompson, University of California, Davis, School of Medicine professor and one of the world’s experts on fungal infections, told me this scenario is very unlikely.

One bug, Candida auris, has been spreading especially among the immunocompromised. Though this yeast has shown drug resistance, is sometimes difficult to identify and causes outbreaks in health-care settings, its spread is still quite limited, Thompson said.

The biggest threat to us remains a bioengineered animal pathogen that’s helped to skip the obstacles of requisite mutations before it can become widespread.

The very gain-of-function research that manipulates viruses or bacteria and induces mutations to teach us how to be protected or to provide treatments or vaccines in advance can create the exact path to harm that we fear.

This is what happened with H5N1 in 2012, when Ron Fouchier and colleagues in the Netherlands used genetic engineering and serial infections of ferrets (which spread viruses similar to the way humans do) to create a mutant bird-flu virus that spread among ferrets through the air.

Those experiments led to a temporary moratorium on such research with H5N1. But work manipulating coronaviruses continued. Palese feels that this gain-of-function research is sometimes worth the risk, especially in the United States, where the experiments can and should be highly monitored.

Unfortunately, it may take only one rogue scientist to prove Palese wrong — if COVID hasn’t already done so.

Marc Siegel, MD, is a clinical professor of medicine and medical director of Doctor Radio at NYU Langone Health and a Fox News medical analyst.