42 CLINICAL FOCUS
42 CLINICAL FOCUS
18 JULY 2025 ausdoc. com. au
| THE | WINTER SEASON SPECIAL
Therapy Update
Group A strep: a post-COVID threat
NEED TO KNOW
Invasive strep A disease is now a nationally notifiable disease( as of July 2021), allowing prospective surveillance across Australia.
After a decline in incidence of serious invasive disease during the COVID-19 pandemic from 2020 to 2021, multiple countries, including Australia, have reported a surge in serious strep A disease after lifting of COVID-19 restrictions in late 2022.
Infectious disease
With global reports of invasive strep A on the rise, we review the recent epidemiology, state of surveillance and control of the disease in Australia.
STREP A( Streptococcus pyogenes or group A streptococcus) is estimated to cause over 18 million cases of severe disease and 500,000 deaths worldwide each year. 1 The most frequent manifestations of strep A disease are superficial infections, such as pharyngitis and impetigo, spread by direct person-to-person contact.
However, strep A causes a spectrum of disease, ranging from toxin-related manifestations such as scarlet fever and streptococcal toxic shock syndrome, to invasive disease, including necrotising fasciitis and post-infectious immune-mediated complications such as acute rheumatic fever( ARF)/ rheumatic heart disease( RHD) and acute post-streptococcal glomerulonephritis( APSGN). 2
Since late 2022, there has been a surge in invasive strep A cases reported globally. However, Aboriginal and Torres Strait Islander communities in Australia have long experienced a disproportionate burden of strep A disease related to socioeconomic and healthcare disparities. 3, 4
Here, we review the recent epidemiology of strep A disease and the state of surveillance and disease control in Australia while placing it in the context of the ongoing disproportionate burden of disease in Aboriginal and Torres Strait Islander communities.
Epidemiology
A landmark change in invasive group A streptococcus( iGAS) disease surveillance in Australia has been its introduction as a nationally notifiable condition in July 2021, implemented by all states as of September 2022. 5 Confirmed cases of invasive strep A disease are defined as isolation of strep A from a normally sterile site, such as the bloodstream.
Notification requirements vary across jurisdictions( for example, laboratory notification and / or clinician notification). It is important for clinicians to refer to their jurisdiction’ s specific public health guidelines with regard to their notification requirements. The introduction of a coordinated approach allows comprehensive prospective surveillance of invasive strep A disease to inform disease control and public health measures in Australia.
Prior to 2020, the median incidence of invasive strep A in most states in Australia was estimated to be 3-5 cases per 100,000 population per year. 5-7 However, incidence in the Northern Territory reached up to 70 per 100,000 population per year with a
Dr Ouli Xie Infectious diseases physician at Monash Infectious Diseases, Monash Health; and PhD candidate at the Peter Doherty Institute for Infection and Immunity, Melbourne.
Professor Asha Bowen Paediatric infectious diseases specialist at Perth Children’ s Hospital; and head of healthy skin and ARF prevention at the Telethon Kids Institute, Perth.
Professor Steven Tong Infectious diseases physician at the Victorian Infectious Diseases Service at the Royal Melbourne Hospital; and co-head of clinical and health services research at the Peter Doherty Institute for Infection and Immunity, Melbourne.
disproportionate burden of disease in Aboriginal and Torres Strait Islander people. 8
During the COVID-19 pandemic( 2020 to early 2022), there was a historically low incidence of invasive strep A in Australia, mirroring trends seen in other countries such as the UK. 9, 10 Strep A is transmitted person to person via droplet and possibly airborne routes, and restrictions put in place to reduce COVID-19 transmission may similarly reduce strep A transmission.
However, since lifting of many restrictions in 2022, there has been a dramatic surge in incidence to more than twice pre-pandemic levels across all age groups in Australia and globally( Figure 1). 9, 11-15 Limited data from superficial swabs have demonstrated a concurrent increase in
10, 16 non-invasive disease.
What’ s behind the surge?
Genomic surveillance has not detected emergence of a new strain driving the
Cases per 10,000 admissions
32
28
24
20
16
12
8
4
0
2011 2012
2013 2014 surge in cases. However, a lineage named M1UK, that is associated with increased toxin production( superantigen SpeA), has been increasing in frequency in Australia since 2013. This lineage was first described during a surge of scarlet fever in the UK in
17, 18
2014-2016.
The frequency of M1UK strains increased further with the post-COVID surge in multiple European countries and also increased in proportion in some Australian jurisdictions such as Victoria. 9 Overseas, M1UK has been associated with more unusual and severe manifestations such as paediatric empyema
10, 19 and meningitis.
It is unclear if M1UK causes more severe manifestations in Australia. The M1UK strain has not yet been detected in the Northern Territory, despite this region experiencing the highest incidence of disease.
Although M1UK may have increased in frequency, the lack of a new strain driving disease suggests other factors must be
Region
Top End Melbourne and Sydney
2015 2016
2017 2018
Year
Genomic surveillance has confirmed that the surge in cases is not due to the emergence of a new clone and may instead be related to host factors such as reduced immunity.
The authors advocate for increased vigilance for signs and symptoms of serious invasive disease and / or sepsis.
Despite the recent attention on the surge in cases, Aboriginal and Torres Strait Islander communities, particularly in remote northern Australia, continue to experience a disproportionate burden.
underlying the recent surge. It has been hypothesised that reduced strep A transmission during 2020-2022 may have resulted in diminished population immunity and increased host susceptibility after lifting of COVID-19 restrictions. Reduced population immunity to respiratory viral pathogens may have also contributed to a surge in acute
2019
2020
Figure 1. Hospital-based incidence of invasive strep A measured per 10,000 admissions in the Top End of the Northern Territory( red) and four large hospital networks in Melbourne and Sydney from 2011 to February 2023. The blue shaded period from 2020 to 2021 approximates the period of most significant lockdowns and other restrictions related to the COVID-19 pandemic. Error bars represent 95 % confidence intervals. Adapted from Xie et al. 9
2021 2022
Feb 2023