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The Covid-19 pandemic subsided in much of the world and with it many of the social restrictions put in place to curb its spread as people were eager to return to pre-lockdown lives.
But in its place have 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 among the mildest on record, both in terms of deaths and hospitalizations. Still, cases spiked in February and soared further in the spring and summer as Covid restrictions were lifted.
“We have never seen a flu season in the United States extend into June,” Dr. Scott Roberts, associate medical director for infection control at Yale New Haven Hospital, told CNBC on Tuesday. .
“Covid has clearly had a very big impact on that. Now that people have come out, places are opening up, we’re seeing viruses behaving in very strange ways that they weren’t before,” a- he declared.
And the flu is just the beginning.
Respiratory syncytial virus, a common cold-like virus during the winter months, showed an uptick last summer, with cases rising among children in Europe, the United States 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 in young children.
Elsewhere, Washington state is experiencing 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 emerging in 29 non-endemic countries.
Viruses behave badly
At least two genetically distinct variants of monkeypox are now circulating in the United States, likely due to two different infections passed from animals to humans, the US Centers for Disease Control and Prevention said last week.
The World Health Organization noted earlier last week that the virus, whose symptoms include fever and skin lesions, could go unnoticed by society for “months or maybe a few years”.
A section of skin tissue, harvested from a lesion on the skin of a monkey, which had been infected with monkeypox virus, is seen at 50X magnification on day four of the rash developing skin in 1968.
CDC | Reuters
“Both strains probably indicate that this has been going on for longer than we originally thought. We’re in a concerning time right now,” Roberts said. He noted that the coming weeks will be indicative of the evolution of the virus, which has an incubation period of 5 to 21 days.
It is not yet known if the smallpox-like virus has mutated, although health experts have reported that it behaves in new and atypical ways. Most notably, it appears to spread within the community – most often through sex – as opposed to traveling from places where it is usually found. Symptoms also show up in new ways.
“Patients present differently than we had learned before,” Roberts said, noting that some infected patients bypass early flu-like symptoms and immediately develop rashes and lesions, specifically and unusually on the genitals and stomach. ‘anus.
“There are a lot of unknowns that make me uncomfortable. We’re seeing behavior that’s very atypical in many ways for a number of viruses,” he said.
Restrictions reduce exposure, immunity
One explanation, of course, is that Covid-induced restrictions and mask-wearing over the past two years have given other infectious diseases little opportunity to spread as they once did.
Where viruses managed to sneak in, they were often missed because public health surveillance was largely focused on the pandemic.
This was indeed the case during the tuberculosis epidemic in Washington, according to local health authorities, who said that the parallels between the two diseases allowed cases of tuberculosis to go undiagnosed.
Now, as pandemic-induced restrictions have eased and business as usual has resumed, the retreating viruses have found fertile ground among newly social, travel-hungry hosts.
The recent outbreak of monkeypox is thought to stem, at least in part, from two mass events in Europe, a senior WHO adviser said last month.
Meanwhile, two years of reduced exposure have reduced individual immunity to disease and made society as a whole more vulnerable. This is especially true for young children — usually germ amplifiers — who have missed opportunities to acquire antibodies against common viruses, either through their mothers’ wombs or through early socialization.
Missed childhood vaccinations
This could explain the rise in curious cases of severe acute hepatitis in children, according to health experts studying possible links to Covid restrictions.
“We are also exploring whether increased susceptibility due to reduced exposure during the Covid-19 pandemic could play a role,” the UK Health Security Agency said in April.
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The Centers for Disease Control and Prevention has also expressed concern that the shutdowns may have caused many children to miss childhood vaccinations, 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 vaccinations, was unavailable for many children,” Jennifer Horney, a professor of epidemiology at the University of Delaware, told CNBC.
“To prevent the increase of these diseases, catch-up vaccination campaigns are needed globally,” she added.
Watch out for surveillance bias
That said, there is also now greater awareness and surveillance of public health issues as a result of the pandemic, making diagnoses of certain outbreaks more common.
“Covid has raised the profile of public health issues so that maybe we pay more attention to these events when they happen,” Horney said, adding that the public health systems put in place to identify Covid have also helped to diagnose other diseases.
Professor Eyal Leshem, an infectious disease specialist at Sheba Medical Center, agreed: “The general public and the media have become much more interested in zoonotic outbreaks and infectious diseases.”
However, he also cautioned against the role of “surveillance bias”, whereby individuals and healthcare professionals are more likely to report cases of illnesses as they become more visible. 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, but that it’s getting more attention,” Leshem said.
Still, heightened surveillance of infectious disease outbreaks is not a bad thing, he noted. With the increase in the spread and mutation of infectious diseases – as seen with Covid-19 – the more awareness and understanding of the changing nature of disease, the better.
“Public and media attention will help governments and global organizations devote more resources to monitoring and protecting against future pandemics,” Leshem said, noting that research, surveillance and response were three key areas.
“These investments need to happen globally to prevent and mitigate the next pandemic,” he said.