Scarlet fever rises in UK after pandemic lull; invasive infections kill 8

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Scarlet fever is on the rise in the UK, with the number of cases more than four times higher than normal for this time of year. And a rare but serious invasive disease caused by the same bacteria that causes scarlet fever and strep throat – group A streptococcus – is also on the rise, killing at least eight children in the UK, according to media reports.

The unusual increase is seen as another abnormal cycle of disease transmission that is surging in the wake of the COVID-19 pandemic. Like many other seasonal infections, cases of scarlet fever in the UK almost leveled off at the end of the 2019-2020 season and were at the bottom during the 2020-2021 season, according to data published by the Health Security Agency of Great Britain.

Now that most of the health restrictions associated with the pandemic have been lifted or at least eased, a host of seasonal infections have returned – especially those that hit children the hardest. Many returned with a certain ferocity, finding even more vulnerable victims than usual after the hiatus. Many of these disease cycle anomalies have been observed in seasonal viruses, namely enteroviruses, adenoviruses, influenza, and RSV (respiratory syncytial (syn-SISH-uhl) virus), which are currently flooding US hospitals and pediatric wards.

“Many infections became less common during the restrictions of the recent pandemic and are now rapidly returning as mixing normalizes,” Adam Finn, professor of paediatrics at the University of Bristol, said in a statement. “[Group A strep] is no exception, and in recent months we have been recording an increasing number of cases.”

Infectious links

Transmission of group A strep bacteria is associated with transmission of the virus. Historically, Group A strep infections are closely related to the spread of chickenpox, although clinicians note that strep infection can strike after other viral infections. It is not clear exactly what the link is between certain viral infections and group A streptococcus. Researchers have hypothesized that a combination of factors may explain the link, from temporal overlaps in the disease cycle, similar routes of transmission (eg, respiratory) and common age of victims.

There is also the possibility that some germs share common methods of suppressing the immune system to cause infection. Therefore, an infection with one bacillus could pave the way for another following a similar path. It’s there some evidence for this with chicken pox and group A strep, which similarly alter the activity of certain T cells. But some viral infections also suppress the immune system in general. Perhaps the best example of this is measles, which suppresses the immune response for weeks to months after infection, leading to what some experts call “immunological amnesia.” Before childhood vaccination campaigns, measles was widespread closely related to the increase in whooping cough cases (pertussis), which is caused by bacteria Bordetella pertussis.

The current rise in group A strep infections in the UK is not clearly linked to the rise in chickenpox cases. Chickenpox is not a notifiable disease in the UK, meaning official numbers are not available. However, supervisory control data suggests that there has been no unusual increase.

However, the rise of strep A coincides with viral respiratory infections.

“Usually we see a large number [group A strep] cases in late spring or early summer, often following chickenpox infections,” Elizabeth Whittaker, an expert in pediatric infectious diseases and immunology at Imperial College London, said in a statement. “High numbers at this time of year are unusual and probably occur as normal seasonal phenomenon. it hasn’t come back yet… We’re seeing more pneumonia than usual, most likely because group A strep infections coincide with the peak of winter respiratory viruses that are typical for this time of year.”

Group A strep infections usually cause mild infections such as strep throat, scarlet fever, and the skin infection impetigo, which are effectively treated with antibiotics. There were 851 cases of scarlet fever in the UK in the 46th week of this year (ending November 19), while the average in previous years was 186 cases in the 46th week, the UKHSA reported. The spike is part of a larger climb; there were 4,622 reports of scarlet fever in weeks 37 to 46 this year in England, compared with an average of 1,294 over the same period in the previous five seasons.

Difficult cases

In rare cases, group A strep can enter the bloodstream, causing a severe, invasive disease called invasive group A strep (iGAS), which can be fatal in young children. So far this year, the UKHSA has tallied 2.3 cases per 100,000 children aged 1 to 4 years, compared with an average of 0.5 in pre-pandemic seasons (2017 to 2019) and 1.1 cases per 100,000 children between the ages of 5 and 9 compared to the pre-pandemic period. pandemic average of 0.3 at the same time of the year.

Severe cases remain rare, but identifying streptococcal A infection may be more difficult than usual this year as it circulates among respiratory viruses, potentially delaying treatment.

“Severe invasive group A strep is rare and parents don’t need to worry, but they need to know when and how to seek medical attention,” Whittaker said. “Under normal circumstances we expect fevers due to viral infections to subside within 4 or 5 days, so if they persist or are associated with lethargy, difficulty breathing, poor drinking or wet nappies/urination, families should contact NHS111 for advice,” urging to a UK non-emergency medical service line.

“Rapid treatment with antibiotics can control these infections, but it is important that they are recognized and treated quickly,” said Nathalie MacDermott, an expert in pediatric infectious diseases at King’s College London. “Prompt treatment of scarlet fever and sore throat also reduces the chances of a child developing invasive Group A Streptococcus and reduces the chances of spreading the infection to other children at school or household members.”

In the US, scarlet fever is not a reportable disease—so there are no official numbers—but there is surveillance of iGAS cases. At a press briefing earlier this week, Barbara Mahon, an epidemiologist at the Centers for Disease Control and Prevention, said, “As far as I know, we haven’t heard of any significant increase [in iGAS cases].”