Hope is not an effective strategy for dealing with a pandemic.

Two years in, we should all know that. Yet I’ve been watching with concern bordering on alarm as the omicron variant has entered the country and started transmitting in the community. It has become the dominant strain, taking over from the delta variant (itself no slouch) in a matter of days in some places. If it’s not in your neck of the woods yet, it will be soon.

Alongside this there has been a steady tide of coverage and commentary suggesting that omicron causes mostly mild disease — the implication being that it’s not much to worry about, that we need only stay the course and we can ride this one out, too.

But that’s premature. Let me be clear: I’m not stating definitively that omicron has some grim future in store for us. I’m saying that there are red flashing warning signs, that we underestimate this virus at our peril and that even the best-case scenario is still bad.

Barely a month after it was discovered, there’s still quite a bit we don’t know about omicron. The three key areas to focus on are transmissibility, disease severity and immune evasion.

It is clear from data emerging around the world that omicron is highly transmissible and spreads more quickly than delta, which has caused enormous waves of infection in the United States and other nations, including in the parts of southern Africa where omicron was first reported.

Genome sequencing in South Africa, Great Britain, Denmark, Norway and other countries make clear that when omicron takes root, it takes off really fast. We are already starting to see signs of that in the United States: The Centers for Disease Control and Prevention reported Monday evening that omicron made up 73 percent of U.S. coronavirus cases between Dec. 12 and Dec. 18.

If the disease caused by this variant is mostly mild (and don’t hang too much on that “if” yet), we could avoid the worst imaginable outcomes. It is important to remember that vaccination, especially among those boosted, protects well against severe illness. Unvaccinated people in South Africa and the United Kingdom have been shown to be at far higher risk of getting hospitalized than vaccinated ones.

But a “mild” case of covid can still make you feel miserable, even bedridden, for days. Huge numbers of “mildly ill” people unable to go to work or school can cause enormous societal disruption, especially while we’re already experiencing labor shortages and supply-chain disruptions. There’s also the risk of long covid, which can cause physical and cognitive issues for many weeks and months after recovery from the acute phase of illness, and which we still don’t understand that well even two years into the pandemic.

And finally, there’s math. Let’s pull a number out of thin air for demonstration’s sake and say that only 2 percent of omicron cases are severe enough to cause hospitalization. Good news, right? Not if omicron also causes exponentially more infections in a condensed time. Two percent of a huge number is a very large number indeed. With hospitals across the U.S. already strained to the breaking point, the implications are frightening.