New Omicron variant: symptoms of Covid subvariant BA.2, how contagious is it and does it cause severe illness?

The Omicron Covid sub-variant BA.2, also known as ‘stealth Omicron’, is almost as infectious as measles, a former WHO expert has said.

But what is the BA.2 variant and how dominant is the strain?

Here’s what you need to know.

What is BA.2?

Omicron was recently divided into three lineages: BA.1, BA.2, and BA.3.

All three lineages were first detected at approximately the same time and from the same place.

A study published in the Journal of Medical Virology titled Emergence of Omicron third lineage BA.3 and its importance found that there were no specific mutations for the BA.3 lineage in spike protein.

Instead, it is a combination of mutations in BA.1 and BA.2 spike proteins.

The World Health Organisation (WHO) said studies have shown the BA.2 variant appears to be more transmissible than BA.1.

Omicron BA.2 is now the dominant form of the variant in the UK. It is thought to be mild, especially in those who are vaccinated against Covid, but spreads quickly.

Former World Health Organisation (WHO) epidemiologist, Professor Adrian Esterman, told ABC News: "Omicron BA.2 is about 1.4 times more infectious than BA.1. The basic reproduction number (R0) for BA.1 is about 8.2, making R0 for BA.2 about 12.

“This makes it pretty close to measles, the most contagious disease we know about.”

Health Secretary Sajid Javid told Sky News: "We keep the situation very carefully under review. There’s no other variant of concern out there that is an issue at this point in time.

"We have seen some rises in infections over the last week but given the increase in social mixing this was to be expected.”

What are the symptoms of Omicron?

Symptoms of Omicron have proven to be more wide ranging than the original Covid-19 strain, which can make it difficult to spot.

The NHS still recognises three symptoms as the main signs of coronavirus infection and urges people to self-isolate and take a test if they experience any of the following:

• a high temperature
• a new, continuous cough
• a loss of change to your sense of smell or taste

However, the most common signs of Omicron typically differ from the ‘classic three’.

Scientists behind the ZOE Covid Study app found that most people who test positive for Omicron are reporting symptoms that are closer in nature to the common cold.

According to the app, the main signs of infection from Omicron are:

• a runny nose
• a headache
• Sneezing
• a persistent cough
• a sore throat

Other symptoms that have also been linked to the variant include body aches and pains, particularly lower back pain, night sweats, fatigue, nausea, skin rashes and diarrhoea.

How contagious is BA.2?

Early reports indicate that BA.2 is more infectious than the already contagious BA.1 Omicron variant.

Omicron is considered to be the milder variant of Covid and during the third wave it was primarily caused by its subvariant BA.1. However, this variant has a rapid rate of transmission.

The three sub lineages of the Omicron variant were all detected from the same place and viruses that develop simultaneously and from the same place have equal chances of spreading worldwide.

A recent study published in the Journal of Medical Virology titled ‘Emergence of Omicron third lineage BA.3 and its importance’ found that of the 33 mutations in the BA.3 lineage spike protein, 31 mutations are common to BA.1.

It said: "BA.3 lineage caused the lowest number of cases in these three lineages. Therefore, it can be speculated that the reason for the BA.3 lineage spreading at very low speeds and causing fewer cases may have been due to the loss of six mutations from BA.1 or obtaining two mutations from BA.2.”

The study said Omicron has so far been thought to cause mild disease, but "it is also possible to develop some mutations" that can lead to serious illness.

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