The BA.4 and BA.5 subvariants now dominate worldwide

In the past year, the rapid mutation of the coronavirus has triggered new variants, which have swept across the world: Delta last summer, then omicron in winter and more recently omicron’s subvariants BA.2, BA.4 and BA.5. The last pair have quickly become the world’s dominant forms of the coronavirus, as recorded in the GISAID international repository of coronavirus genetic sequences analyzed by The Washington Post.

The worldwide chart of coronavirus variants below shows the sequence of omicron subvariants that have emerged since the peak of the delta wave in September 2021. The BA.4/BA.5 subvariants, which are very similar, were a small share just a few months ago and are now dominant.

The GISAID sequences represent countries where genomic findings are publicly released, so some large countries are not included. Sequencing within the United States varies widely. Nationwide, omicron BA.4/BA.5 made up 4 percent of coronavirus samples sequenced in late May but is now the majority of sequences.

U.S. variant trend

It takes about a week for laboratories to identify virus variants, so this data is always time-lagged. Using variant data, the Centers for Disease Control and Prevention estimated that omicron BA.4 and BA.5 were more than three-quarters of the covid cases in the United States.

The impact of the BA.5/BA.5 subvariant is unclear, but like other versions of omicron they cause reinfection and sometimes evade vaccines. The CDC has urged people to remain up-to-date with vaccine boosters because people with outdated vaccines face increased danger from the variants.

The charts below show the mix of coronavirus variants in a selection of countries that currently have high levels of omicron BA.4/BA.5. To capture the latest trends, these charts use a rolling average of the past three full weeks of data. In any country, the genomic sequences may be concentrated within a particular outbreak, or may miss some outbreaks, so it is not necessarily representative of the country as a whole.

Sequencing is a process that maps out the genetic code of a particular virus that infected someone so it can be compared with other strains. It is a crucial tool to catch significant changes. If mutations change the virus enough, it becomes a new variant. Variants may have different behaviors that affect the transmissibility of the virus and make it evade the human immune system.

Public and private laboratories submit their sequencing results to the worldwide GISAID Initiative, a nonprofit partnership that broadcasts trends of viral diseases.

[Understanding omicron’s many mutations]

Only a very small sample of coronavirus cases are sequenced, and the process takes about a week. Although the level of sequencing varies widely across the world and in the United States, many countries are generating sufficient public genome samples to reveal a trend.

Some countries have not provided sufficient timely samples to the public GISAID data to show the status of omicron’s spread. China and Russia have released very little. In some cases, there may not be technology or resources to do the genomic sequences. In other cases, it may be an issue of transparency.

The delta variant was first detected in India in late 2020 and then moved to Europe and the United Kingdom. It hit the United States in July just when coronavirus cases, hospitalizations and deaths were dwindling.

Delta spread faster than the previous variants and was more likely than those variants to cause infections among vaccinated people. It quickly drove up a spike in cases that peaked in September 2021. Even as it waned, the low point in late October had six times as many cases as the low point before delta struck. In November, cases nationally began rising with another delta wave before omicron was spreading. The initial peak of omicron was the highest level of cases and hospitalization that have struck the country.

Omicron appeared at Thanksgiving and took over the world even faster than delta had. Omicron created the highest case levels and hospitalization of the pandemic.

Chris Alcantara, Leslie Shapiro and Leo Dominguez contributed to this report.