Maria Van Kerkhove, Head of the Emerging Diseases and Zoonosis Division of the World Health Organization, speaks during a press conference following a meeting of the Emergency Committee on the new coronavirus in Geneva on January 22, 2020.

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A senior World Health Organization official said Tuesday that data from some countries may suggest that the Delta variant puts those infected at increased risk of hospitalization, but doesn’t necessarily kill more people than other strains.

“In terms of severity, we’ve seen some countries suggest an increased risk of hospitalization for people with a Delta variant. We haven’t seen this lead to an increased death rate, ”said Maria Van Kerkhove, WHO technical director on Covid-19. People infected with the Delta variant “didn’t die more often than the other strains,” she said.

Health officials have been grappling with the question for months, waiting for real data in countries where the delta variant is widespread. Van Kerkhove said WHO officials meet daily to discuss the rapidly spreading variant.

Like other strains, the Delta variant is especially dangerous for people with underlying conditions like obesity, diabetes, or heart disease, say WHO officials. However, it is far more contagious than other varieties, so it infects more people and puts a strain on global health systems.

“The risk factors for serious illness and death are the same,” said Van Kerkhove. “If you have underlying illnesses, regardless of your age, you have an increased risk of hospitalization.”

The Delta variant also quickly overtakes all other variants wherever it is recognized, she said.

“The prevalence of the lambda variant is falling … and the delta variant is increasing,” said Van Kerhove. “The delta variant quickly replaces other variants that are in circulation wherever it is identified.”

It is spreading in Central and South American countries and is quickly overtaking the lambda variant that is currently predominant there.

“We still don’t know exactly what impact the delta will have on Latin American countries,” said Dr. Sylvain Aldighieri, Incident Manager for the Pan American Health Organization, at a briefing last week.

The delta variant, first discovered by scientists in India in October, has so far spread to at least 142 countries. Found only a few months ago in the US, it now accounts for more than 90% of all sequenced cases, according to the CDC.

The most at risk in the US have been fully vaccinated, with booster doses approved on Friday for people with compromised immune systems and available immediately for administration.

There are currently discussions about opening booster doses to the general population, a move that would violate WHO’s strict recommendations to share doses with the rest of the world before booster doses are given to people who have already received their first vaccinations .

More than 200 million people worldwide have contracted Covid since the pandemic began, doubling from 100 million cases in the past six months. With the more transferable Delta variant spreading rapidly, the number could easily hit 300 million early next year, WHO officials said last week.

“Whether we reach 300 million and how quickly we get there depends on all of us,” WHO Director General Tedros Adhanom Ghebreyesus said last week.

– CNBC’s Robert Towey contributed to this report.