Two new Omicron subvariants have been discovered leading to an increase in COVID-19 infections in South Africa.

In an email to CTVNews.ca, the spokesperson for the Public Health Agency of Canada (PHAC) confirmed they are aware of three cases of BA.4 in Canada, and one case of BA.5.

They said, "The Government of Canada has a robust surveillance program with the provinces and territories to identify COVID-19 variants in Canada, including the concerning Omicron variant and its sublineages."

"Scientists are looking for signs that sublineages of Omicron such as BA.4 and BA.5 change the severity of disease or transmissibility or affect the effectiveness of diagnostic tests, vaccines, or COVID-19 treatments."

Latest government data shows that the highly transmissible Omicron BA.2 variant is currently the most common cause of COVID-19 infections in the country.

"As is the case with all new COVID-19 sublineages, scientists from the Public Health Agency of Canada, together with national and international experts, are monitoring and assessing the BA.4 and BA.5 sublineages and related studies.

The PHAC spokesperson said: An early study, which has not been peer-reviewed, indicates that BA.4 and BA.5 "show higher transmissibility than BA.2" and can also evade antibodies generated from previous Omicron infection.

Another study, also under peer review, suggests that although vaccination "is likely to provide good protection against illness," the ability of the two subvariants to evade antibodies "could lead to a new wave of infections."

This wave has already begun in South Africa, where BA.4 and BA.5 were first identified. WHO Director-General Tedros Adhanom Ghebreyesus said during a briefing on Tuesday, "The subvariants are leading to a significant increase in cases."

"Omicron, specifically BA.4 and BA.5, is driving the surge in South Africa, while BA.2 remains dominant globally."

Since late April, new COVID-19 cases in South Africa have reached thousands daily compared to hundreds the previous month.

In an update dated May 4, the World Health Organization said there were more than 32,000 cases in the country during the previous week, an increase of 67 percent.

Less than 40 percent of the 60 million population have received full vaccinations. The WHO initially announced it was tracking a few dozen cases of BA.4 and BA.5 on April 11.

Over the past month, the subvariants have been detected in countries such as Germany, Portugal, the United Kingdom, Austria, the United States, and Denmark.

Ghebreyesus said earlier in May: "The BA.4 and BA.5 subvariants were identified because South Africa is still doing genomic sequencing which many other countries have stopped doing."

According to the World Health Organization, it is too early to know whether BA.4 and BA.5 cause more severe illness.

Maria Van Kerkhove, technical lead for COVID-19 at the WHO, said in a video on May 3: "These are still early days for this. What we can say at the moment is that it is really important for people to get vaccinated as vaccines still work very well."