Are immune systems out of practice?

And we’ve all learned to reduce that risk over the past year-and-a-half: We’ve been wearing face masks, keeping distance from people in public, washing our hands often, and sanitising stuff. (Well, many people have, in any case.) That has helped slow the spread of COVID-19 — as well as that of the common cold. This was all confirmed in a recent edition of the monthly influenza report by Germany’s Robert Koch Institute, the country’s centre for disease control and prevention.

It said there had been no “measurable” wave of flu infections in Germany or in other European countries during the 2020/2021 flu season. The World Health Organization reported a similar trend in its recent influenza update. With regard to its global figures, the WHO says that “despite continued or even increased testing for influenza in some countries, influenza activity remained at lower levels than expected for this time of the year.”

The same is true of other infections. The RKI reports a drop of 35% in general infectious disease cases between March and August 2020. The biggest reduction was among respiratory infections — that is, those that spread through the air. Measles infections, for instance, were down by 86%. Whooping cough was down by 64%. Even gastrointestinal infections decreased: Rotavirus infections dropped by 83%, and norovirus infections by 79%. But the reasons for the drop in infections varies from virus to virus, say the experts. Restrictions on in-person contact and other hygiene regulations have played a part, especially for gastrointestinal infections.

There was also a drop in the number of sexually transmitted infections and those transmitted via the blood. And HIV infections dropped by 22%, which the RKI thinks may have to do with restrictions clinics and counselling centres have faced during the pandemic. However, it is just as conceivable to think that a large number of any type of infection has gone undetected, with people avoiding unnecessary trips to the doctor or the hospital during lockdown. As a result, it’s possible that there is a very high number of unknown or unreported cases of illness. In some parts of the world, the number of cases of respiratory syncytial virus (RSV) has increased among children.

The US Centers for Disease Control and Prevention describes RSV as a common respiratory virus that “usually causes mild, cold-like symptoms. Most people recover in a week or two; but RSV can be serious, especially for infants and older adults.” The RKI’s assessment is similar. It says RSV can affect people of all ages, but that it most often impacts infants. RSV is highly infectious. It is transmitted when an infected person sneezes or coughs — the same route SARS-CoV-2 uses.

In March, there were a number of RSV cases in Australia. In New Zealand, the number of cases has risen consistently since the end of May. Meanwhile in Central Europe, where RSV cases tend to rise between November and April, that traditional “RSV season” was relatively quiet. But cases are starting to present themselves now. France, Switzerland and the United Kingdom are reporting ever more RSV cases. The Royal College of Emergency Medicine wrote in June that emergency centres in the UK were seeing a “dramatic rise in the number of young children — but it’s not COVID.” RSV symptoms include runny nose, coughing, reduced appetite and fever. It can also develop into acute bronchitis or pneumonia. An RSV infection is one of the most common reasons for hospital admissions among infants and young children. Germany’s RKI estimates a worldwide RSV incidence rate of 48.5 cases per 1,000 children in the first half of 2021; 5.6 cases per 1,000 kids is considered to be severe.