Around this time last year, my young daughter caught chickenpox. I thought it was a standard case of a normal childhood illness – we’d manage it by trying to ease the itching and everything would be fine.
Instead, my daughter got worse. She developed a sore throat, then a body rash, and struggled to drink liquids. Again, I thought this was a normal progression of her infection and she would eventually get better. It was only after I started talking to my colleagues that I learned that group A strep cases had been reported among schools in the vicinity. I also found out that chickenpox could lead to increased vulnerability against strep A, particularly among children.
My daughter was taken to the GP, diagnosed with group A strep, and prescribed antibiotics. She made a full recovery, as most people do. However, as we witness a resurgence of this disease, we know that in rare cases strep A can cause pneumonia and an invasive bacterial infection that can be fatal. There have been a number of deaths in the UK, 16 of them children.
The strep A situation does highlight what is not yet enough studied in scientific research – the relationship between infectious diseases, such as between chickenpox and strep A. We still don’t understand why contracting one disease can make us more vulnerable to get a second one, a not uncommon scenario. Respiratory syncytial virus (RSV) and influenza can have similar links to pneumococcal bacteria, which cause pneumonia. Having a cold caused by one of these viruses makes one more susceptible to pneumonia and generally much sicker. Even less is known about the potential impact of Covid-19 when it inevitably enters the mix, as we go into winter.
One thing is certain, though. Getting infected with bugs such as strep A, RSV, influenza and Covid-19 can weaken the immune system to the point that pneumonia can develop, either caused by these or other bugs. For example, studies have shown that the decline in pneumococcal pneumonia during the pandemic was not due to the disappearance of the pneumococcus that had continued to circulate in the communities, but to a complete decline in certain respiratory viruses. Pneumococcus was still present, without symptoms, in children’s noses – but without a co-infection it couldn’t progress to full-blown pneumonia.
There is an opportunity for scientific research to explore the relationship between respiratory viruses and pneumococcal bacteria, so we are not forced to treat them independently of each other and perhaps could better use the arsenal of vaccines already available, as well as the new ones coming soon. This would help policymakers plan the best defences against such infections and should be an integral part of efforts to build global resilience against future pandemics. Research of this kind is already being carried out at the University of Oxford and other institutions around the world.
Unpicking this relationship between different infections is vital, especially as, post-pandemic, we are seeing shifts in the seasonality of several diseases. The rising numbers of strep A cases is unusual for this time of the year because they typically occur in late spring or early summer, often after chickenpox infections. This is most likely the result of a large infection-naive population – people who have never encountered the infection before – that has developed as a result of us staying mostly indoors during the pandemic.
A shift in seasonality of certain diseases following the pandemic and a sharp increase in other respiratory viruses at this time of the year can also increase vulnerability to strep A. We saw something similar happen in the US and in the UK with RSV, when there was a surge in cases over the spring and autumn last year following the easing of social contact rules. We should typically expect RSV to start peaking over the winter instead.
Another effective way we can mitigate the impact of respiratory diseases is through vaccination. There are already vaccines available for pneumonia, influenza and Covid-19 for instance. Although there aren’t any for RSV or strep A, they are in development and could be an important weapon against such infections in the future. However, it is also possible to build up defences indirectly. A chickenpox vaccine obviously helps recipients develop immunity against the disease, but could also potentially help to stop such infections from progressing into something more serious, such as strep A. The same principle can be applied to influenza, pneumococcus and Covid-19 vaccines.
An already stretched NHS is doing all it can to combat strep A and other respiratory illnesses. Pharmacists are also reporting shortages in antibiotics needed to treat strep A. We should do what we can to help our health system be more resilient through these cold months while also calling for measures to help it weather such pressures in the future, including more backing for scientific research and investment in pandemic preparedness.
• This article was amended on 12 December 2022. An earlier version said incorrectly that all the recent strep A deaths in the UK have been of children.
Daniela Ferreira is professor of mucosal infection and vaccinology at the University of Oxford and the Liverpool School of Tropical Medicine
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