Diseases suppressed during Covid are back

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The Covid-19 pandemic has eased across much of the world, and with it many of the social restrictions put in place to stem its spread as people are eager to get back to pre-lockdown life.

But in its place has emerged a series of viruses behaving in new and peculiar ways.

Take the seasonal flu, more commonly known as the flu. The 2020 and 2021 US winter flu seasons were some of the mildest on record, both in terms of deaths and hospitalizations. However, cases increased in February and increased further in spring and summer as Covid restrictions were lifted.

“We’ve never seen a U.S. flu season extend into June,” said Dr. Scott Roberts, associate medical director for infection prevention at the Yale School of Medicine, told CNBC on Tuesday.

“Covid has clearly had a very big impact on this. Now that people have unmasked, places are opening up, we are seeing viruses behaving in very strange ways that they haven’t before,” he said.

And the flu is just the beginning.

We are seeing very unusual behavior in many ways for various viruses.

Dr Scott Roberts

associate medical director for infection prevention, Yale School of Medicine

Respiratory syncytial virus, a virus similar to the common cold during the winter months, showed an increase last summer, with cases increasing among children in Europe, the US and Japan. Then, in January of this year, an outbreak of adenovirus 41, usually responsible for gastrointestinal illnesses, became the apparent cause of a mysterious and serious liver disease among young children.

Elsewhere, Washington state has experienced its worst TB outbreak in 20 years.

And now, a recent outbreak of monkeypox, a rare viral infection typically found in Central and West Africa, is baffling health experts with more than 1,000 confirmed and suspected cases popping up in 29 non-endemic countries.

Viruses behaving badly

At least two genetically distinct variants of monkeypox are now circulating in the US, likely stemming from two different infections from animals to humans, the US Centers for Disease Control and Prevention said last week.

The World Health Organization noted earlier this week that the virus, whose symptoms include fever and skin lesions, may have gone unnoticed in society for “months or possibly a few years”.

A section of skin tissue, taken from a skin lesion on a monkey that had been infected with monkeypox virus, is seen at 50x magnification on the fourth day of the eruption’s development in 1968.

CDC | Reuters

“The two strains probably indicate that this has been going on for longer than we thought. We’re at a worrying time right now,” Roberts said. He noted that the coming weeks will reveal the course of the virus, which has an incubation period of 5 to 21 days.

It remains unclear whether the smallpox virus has mutated, although health experts have reported that it is behaving in new and atypical ways. Most notably, it appears to be spreading within the community – most commonly through sex – as opposed to traveling from places where it is normally found. Symptoms are also showing up in new ways.

“Patients are presenting differently than we were previously taught,” Roberts said, noting that some infected patients are ignoring initial flu-like symptoms and immediately developing rashes and lesions, specifically and unusually on the genitals and anus.

“There are a lot of unknowns that make me uncomfortable. We’re seeing very atypical behavior in many ways for various viruses,” he said.

Restrictions reduce exposure, immunity

One explanation, of course, is that Covid-induced restrictions and mask-wearing over the past couple of years have given other infectious diseases little opportunity to spread in the way they once did.

Where viruses managed to escape, they were often overlooked as public health surveillance focused primarily on the pandemic.

That was indeed the case with the TB outbreak in Washington, according to local health officials, who said the parallels between the two diseases allowed TB cases to go undiagnosed.

During the Covid pandemic, access to primary care, including childhood vaccines, was not available for many children.

Jennifer Horney

professor of epidemiology, University of Delaware

Now, as pandemic-induced restrictions eased and usual habits resumed, viruses that were in retreat have found fertile ground in new social and travel-hungry hosts.

The recent outbreak of monkeypox is believed to have stemmed, at least in part, from two mass events in Europe, a top adviser to the WHO said last month.

Meanwhile, two years of reduced exposure reduced individual immunity to disease and made society as a whole more vulnerable. This is especially true for young children – often germ amplifiers – who have missed opportunities to obtain antibodies against common viruses, either through their mother’s womb or by socializing in the early years.

Missed childhood vaccines

This could explain the rise in curious cases of severe acute hepatitis among children, according to health experts who are looking at possible links to Covid restrictions.

“We are also exploring whether increased susceptibility due to reduced exposure during the Covid-19 pandemic may be playing a role,” the UK Health Safety Agency said in April.

Walrus Images | Digital Vision | Getty Images

The Centers for Disease Control and Prevention also expressed concern that the lockdowns may have caused many children to miss childhood vaccines, potentially increasing the risks of other vaccine-preventable diseases such as measles and whooping cough.

“During the Covid pandemic, access to primary care, including childhood vaccines, was not available for many children,” Jennifer Horney, a professor of epidemiology at the University of Delaware, told CNBC.

“To prevent the increase in these diseases, vaccination campaigns are needed globally,” he added.

Beware of Surveillance Bias

That said, there is now also heightened awareness and vigilance of public health issues in the wake of the pandemic, making diagnoses of some outbreaks more common.

“Covid has raised the profile of public health issues so that we may be paying more attention to these events when they occur,” Horney said, adding that public health systems created to identify Covid have also helped diagnose other diseases.

Professor Eyal Leshem, an infectious disease specialist at Sheba Medical Center, agreed: “The general population and the media have become much more interested in zoonotic outbreaks and infectious diseases.”

It is not that the disease is more prevalent, but that it receives more attention.

Professor Eyal Leshem

infectious disease specialist, Sheba Medical Center

However, he also warned of the role of “surveillance bias”, whereby individuals and medical professionals are more likely to report disease cases as they grow older. This suggests that some viruses, such as monkeypox, may appear to be growing when, in fact, they were previously underreported.

“It’s not that the disease is more prevalent, it’s that it gets more attention,” Leshem said.

Still, increased monitoring of infectious disease outbreaks isn’t bad, he noted. With the increase in the spread and mutation of infectious diseases – as seen in Covid-19 – the more awareness and understanding of the changing nature of diseases, the better.

“Public and media attention will help governments and global organizations direct more resources towards surveillance and protection from future pandemics,” said Leshem, highlighting research, surveillance and intervention as three key areas of focus.

“These investments need to take place globally to prevent and mitigate the next pandemic,” he said.

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