dowel | moment | Getty Images
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 scrambled to return to pre-lockdown life.
But in its place a number of viruses have appeared that behave in new and peculiar ways.
Take seasonal influenza, better known as the flu. The 2020 and 2021 US winter flu season was among the mildest on record in terms of both deaths and hospitalizations. But cases picked up in February and continued to climb into the spring and summer as Covid restrictions were eased.
“We have never seen a flu season extend into June in the United States,” said Dr. Scott Roberts, associate medical director for infection prevention at the Yale School of Medicine, told CNBC on Tuesday.
“Clearly Covid has had a very big impact on that. Now that people have unmasked themselves, places are opening up, we’re seeing viruses behaving in very strange ways than they were before,” he said.
And the flu is just the beginning.
Respiratory syncytial virus, a cold-like virus common during the winter months, saw a surge last summer, with cases in children soaring in Europe, the US and Japan. Then, in January of this year, an outbreak of adenovirus 41, which is normally responsible for gastrointestinal illness, became the apparent cause of a mysterious and serious liver disease in young children.
Elsewhere, Washington state is experiencing its worst tuberculosis 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 over 1,000 confirmed and suspected cases popping up in 29 non-endemic countries.
Viruses behave badly
At least two genetically distinct monkeypox variants are now circulating in the US, likely resulting from two different animal-to-human spillover infections, 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, may have gone undetected in society for “months or possibly a few years”.
A section of skin tissue taken from a lesion on the skin of a monkey infected with the monkeypox virus is seen at 50x magnification on the fourth day of the rash’s development in 1968.
CDC | Reuters
“The two strains probably indicate that this is taking longer than we initially thought. We are at a worrying time right now,” Roberts said. He noted that the coming weeks will be significant for the course of the virus, which has an incubation period of 5 to 21 days.
It’s not yet clear if the smallpox-like virus has mutated, although health experts have reported it behaving in new and atypical ways. Most notably, it seems to spread within the community — most commonly through sex — as opposed to travel from places where it typically occurs. Symptoms also appear in new ways.
“Patients are presenting differently than we’ve been previously taught,” Roberts said, noting that some infected patients bypass initial flu-like symptoms and immediately develop rashes and lesions, particularly and uncommonly on the genitals and anus.
“There are many unknowns that worry me. We’re seeing very atypical behaviors for a number of viruses in many ways,” he said.
Restrictions reduce exposure, immunity
One explanation, of course, is that the Covid-induced restrictions and mask-wearing over the past two years have given little opportunity for other infectious diseases to spread as they once did.
Where viruses managed to slip through, they have often been overlooked as public health surveillance has largely focused on the pandemic.
That was indeed the case with the tuberculosis outbreak in Washington, according to local health officials, who said parallels between the two diseases meant TB cases went undiagnosed.
Now that the restrictions imposed by the pandemic have been eased and usual habits resumed, viruses that have been in retreat have found fertile breeding ground in new social and travel-hungry hosts.
The recent monkeypox outbreak is thought to have been at least partly due to two mass gatherings in Europe, a senior adviser to the WHO said last month.
Meanwhile, two years of reduced exposure has lowered individual immunity to disease and made society as a whole more vulnerable. This is especially true for young children—usually germ boosters—who have missed opportunities to acquire antibodies to common viruses, either through the womb or through social contact at an early age.
Missed childhood vaccinations
This could explain the rise in strange severe acute hepatitis cases in children, according to health experts studying possible links to Covid restrictions.
“We are also investigating whether increased vulnerability due to reduced exposure during the Covid-19 pandemic could play a role,” Britain’s Health Security Agency said in April.
Morsa Pictures | digital vision | Getty Images
The Centers for Disease Control and Prevention has also expressed concern that lockdowns may have resulted in many children missing childhood vaccinations, potentially increasing their risk of other vaccine-preventable diseases such as measles and whooping cough.
“During the Covid pandemic, access to basic services, including childhood immunizations, has been unavailable for many children,” Jennifer Horney, a professor of epidemiology at the University of Delaware, told CNBC.
“To prevent an increase in these diseases, catch-up vaccination campaigns are needed worldwide,” she added.
Beware of surveillance distortion
However, in the wake of the pandemic, there is also now greater awareness and surveillance of public health issues, making some outbreaks more common to diagnose.
“Covid has raised the profile of public health issues, so perhaps we’ll pay more attention to these events when they occur,” Horney said, adding that public health systems put in place to identify Covid also help diagnose other diseases to have.
Professor Eyal Leshem, infectious disease specialist at Sheba Medical Center, agreed: “The general population and the media are much more interested in zoonotic outbreaks and infectious diseases.”
But he also warned of the role of “surveillance bias,” where individuals and healthcare professionals are more likely to report cases of illness as they become more well-known. This suggests that some viruses, such as monkeypox, appear to be multiplying despite previously underreporting.
“It’s not that the disease is becoming more common, it’s that more attention is being paid to it,” Leshem said.
Still, increased surveillance of infectious disease outbreaks is not a bad thing, he noted. With the increasing prevalence and mutation of infectious diseases – as seen with 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 into surveillance and protection for future pandemics,” Leshem said, highlighting research, surveillance and intervention as three key areas of focus.
“These investments must be made globally to prevent and mitigate the next pandemic,” he said.