The world is ablaze with the news that the coronavirus has a new variant of concern — one that appears to be driving a dramatic surge in South Africa and offering a glimpse of where the pandemic might be headed. What do we know so far about how omicron differs from delta?

1. Omicron might be more contagious. Little is known about the new variant, but the spike in South Africa suggests it might be more contagious, said Dr. Sikhulile Moyo of Botswana, the scientist who may have been the first to identify the new variant, though researchers in neighboring South Africa were close on his heels. It’s not clear if the variant causes more serious illness or can evade the protection of vaccines.

South African Health Minister Joe Phaahla noted that only a small number of people who have been vaccinated have gotten sick, mostly with mild cases, while the vast majority of those who have been hospitalized were not vaccinated, as has been the case with the delta variant.

It is too early to say if the omicron variant is fitter than delta or if it will become dominant. Omicron shares some mutations with the delta variant but also possesses others that are quite different. But one area of concern is that the omicron variant has 10 mutations in the receptor-binding domain – the part of the spike protein that interacts with the ACE-2 receptor and mediates entry into cells – compared with just two for the delta variant.

Suppose the combination of all the mutations in omicron makes it either more transmissible or better at immune evasion than delta. In that case, we could see the spread of this variant globally. However, it is also possible that the unusually high number of mutations could be detrimental to the virus and make it unstable.

2. Reinfections are worrisome. South African scientists reported that omicron appears more likely than earlier variants to cause reinfections among people who have already had a bout with COVID-19.

A research group has been tracking reinfections in South Africa and reported a jump with the arrival of omicron that they hadn’t seen when two previous variants, including the extra-contagious delta variant, moved through the country.

The findings, posted online Thursday, are preliminary and haven’t yet undergone scientific review. Nor did the researchers say what portion of the reinfections were confirmed as omicron cases — or whether they caused serious illness.

But the timing of the reinfection spike suggests that omicron “demonstrates substantial population-level evidence for evasion of immunity from prior infection,” they wrote.

“Previous infection used to protect against delta, and now with omicron it doesn’t seem to be the case,” one of the researchers, Anne von Gottberg of the University of Witwatersrand, said at a World Health Organization briefing on Thursday.

The study also did not examine the protection offered by vaccination. Coronavirus vaccines trigger different layers of immune response, some to fend off infection and others to prevent severe disease if someone does become infected.

“We believe that vaccines will still, however, protect against severe disease,” von Gottberg said.

3. Many mutations could spell trouble. Omicron has more than 50 mutations, with 32 mutations on the spike protein alone, and scientists have called it a big jump in the evolution of the virus. The spike protein – which forms protruding knobs on the outside of the SARS-CoV-2 virus – helps the virus adhere to cells so that it can gain entry. It is also the protein that all three vaccines currently available in the U.S. use to induce protective antibodies. For comparison, the delta variant has nine mutations.

A lot remains a mystery about omicron. The appearance of such a highly mutated virus nearly two years into the pandemic caught the scientific community by surprise, as many had hypothesized that the ultra-contagious delta variant might mark the last major wave, peaking and then eventually burning out, much like the 1918 influenza pandemic.

It will take scientists weeks of careful laboratory testing and study to untangle exactly what omicron’s mutations mean, and definitively nail down details about how much more contagious it is and what the implications are for those who get infected. But early observations have already allowed scientists to make some informed guesses about what’s to come.

The location of omicron’s mutations suggest two things. The first is that the virus is likely to evade vaccines to some extent. Some of the spike mutations are in the same locations seen in other variants that spread quickly. In past variants those mutations have led to what’s known as antibody escape, in which the virus is able to evade the attack of antibodies generated by vaccines or a previous COVID-19 infection.

The second insight is that it appears likely omicron won’t be impervious to the body’s second line of defense, T-cells. They work hand-in-hand with antibodies to ward off infection and the development of disease. If a virus manages to escape the attacks of antibodies, T-cells then get to work killing infected cells.

“Many of the mutations occur in the hotspots on the spike protein, which we know are important for antibodies to bind,” said Wendy Burgers, an immunologist at the University of Cape Town. “What we predict is that a lot of the T-cell response will still be active against omicron.”

While the study did not examine the protection offered by vaccination, von Gottberg said: “We believe that vaccines will still, however, protect against severe disease.”

While warning that cases could well rise quickly because of omicron, Dr. Takeshi Kasai, WHO regional director for the Western Pacific, said the measures used against the delta variant — which itself caused surges the world over — should remain at the core of the response.

“The positive news in all of this is that none of the information we have currently about omicron suggests we need to change the directions of our response,” Kasai said.

That means continuing to push for higher vaccination rates, abiding by social-distancing guidelines, and wearing masks, among other measures, said WHO Regional Emergency Director Dr. Babatunde Olowokure.

The Associated Press, Tribune News Service and The Conversation contributed to this report.