The current outbreak of respiratory disease (SARS CoV-2) caused by the novel coronavirus (2019nCoV) began in late December 2019 in Wuhan, China. Nearly three years later, SARS CoV-2 transmission remains high, partly due to the emergence of multiple variant strains of the virus. The World Health Organization (WHO) situation report from late November identified 634,522,052 confirmed cases and 6,599,100 deaths globally.
Singapore has been living with a highly infectious, immune evasive strain for months and now it’s taking off in Australia. Although the BA.4 and BA.5 omicron variants continue to be the most common variants in Australia, there has been a rise in XBB, BQ.1 and the B2 sub-lineages. Two new variants are related to omicron BA5, which had caused most of the infections in Australia in recent months and are expected to supplant the Omicron BA.5 sub-variant in Australia later in 2022 or in early 2023.
The XBB sub-variant is especially ‘immune evasive’ than previous strains. It is a combination of two strains of the omicron variant and has at least seven mutations along the spike of the virus, which makes it harder for antibodies to recognise and repel it.
XBB and BQ.1 have now been detected in several parts of Australia. RACGP 2022
Although both XBB and BQ.1 possess a growth advantage over previous COVID strains, there is no evidence to suggest either variant is more severe. The WHO’s Technical Advisory Group on SARS-CoV-2 Virus Evolution (TAG-VE) states that there is no epidemiological evidence that these subvariants will be of substantially greater risk compared to other Omicron subvariants, but this assessment was based on data from limited sources and may not be fully generalisable to other settings.
In Victoria, hospitalisations increased by 20% in the week leading up to 28 October 2022, prompting a warning for people to ensure they are taking appropriate disease mitigation steps (vaccination/boosting, self-isolating when symptomatic and using masks). The NSW rise mirrors Victoria, where a 25 per cent increase in case numbers was recorded last week. Surveillance of wastewater and clinical samples in Victoria has shown that the rapid growth of BQ.1 and XBB so that these two strains now have a combined prevalence of approximately 10%.
Masks wearing is still common in Singapore and mandatory on public transport, but XBB has still spread fast among the population. So, even if you have had COVID-19 before, you could be in for another bout. The World Health Organisation notes there is early evidence pointing at a higher reinfection risk from XBB compared to other circulating omicron sub-variants. The advice is if you are due a booster – go and have it.
Australia will also have some access to new bivalent vaccines that are more effective against Omicron variants (from Moderna and Pfizer) compared to those that target the original strain. While it is not known how many Moderna bivalent vaccines will arrive before the end of the year, the Therapeutic Goods Administration (TGA) has now also provisionally approved Pfizer’s bivalent candidate for use as a booster. But Australia is lagging other jurisdictions, such as Singapore, which has approved the latest Moderna vaccine that targets more recent variants. Omicron variant-targeted vaccines are in development by other companies too.
But if you are infected, and despite the recent changes removing mandatory self-isolation, you really should still isolate. This may be required anyway as the infection may make you ill and feel like resting. If so, rest and recover.