The World Health Organization began naming the variants after Greek letters to avoid public confusion and stigma.
Markets plunged on Friday, hope of taming the coronavirus dimmed and a new term entered the pandemic lexicon: Omicron.
The Covid-19 variant that emerged in South Africa was named after the 15th letter of the Greek alphabet.
The naming system, announced by the World Health Organization in May, makes public communication about variants easier and less confusing, the agency and experts said.
For example, the variant that emerged in India is not popularly known as B.1.617.2. Rather, it is known as Delta, the fourth letter of the Greek alphabet.
There are now seven “variants of interest” or “variants of concern” and they each have a Greek letter, according to a W.H.O. tracking page.
Some other variants with Greek letters do not reach those classification levels, and the W.H.O. also skipped two letters just before Omicron — “Nu” and “Xi” — leading to speculation about whether “Xi” was avoided in deference to the Chinese president, Xi Jinping.
“‘Nu’ is too easily confounded with ‘new,’” Tarik Jasarevic, a W.H.O. spokesman, said on Saturday. “And ‘Xi’ was not used because it is a common last name.”
He added that the agency’s best practices for naming diseases suggest avoiding “causing offense to any cultural, social, national, regional, professional or ethnic groups.”
Some of the better-known variants, such as Delta, rose to a variant of concern. Others in that category were named Alpha, Beta and Gamma. Others that emerged, which were variants of interest, were named Lambda and Mu. Other Greek letters were used for variants that did not meet those thresholds but Nu and Xi were the only ones that were skipped.
The W.H.O. has promoted the naming system as simple and accessible, unlike the variants’ scientific names, which “can be difficult to say and recall, and are prone to misreporting,” it said.
Some researchers agree.
Dr. Angela Rasmussen, a virologist at the University of Saskatchewan, said she conducted many interviews with reporters this year, before the Greek naming system was announced, and she stumbled through confusing explanations about the B.1.1.7 and B.1.351 variants. They are now known as Alpha, which emerged in the United Kingdom, and Beta, which emerged in South Africa.