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Humans have battled viruses since our species first evolved, yet the appearance in December 2019 of Sars-CoV-2, which caused a new “novel” Covid-19 coronavirus disease, has brought the world to its knees.
Five months since the World Health Organisation declared the coronavirus outbreak a pandemic, the number of cases globally has passed 20 million with almost 800,000 known deaths.
The coronavirus has also accelerated scientific development at an unprecedented scale. Across the world, scientists are working around the clock to fight the virus in a collaboration unlike any in history.
But what will be the legacy of Covid-19 on our health for years to come? Could 2020 signal the age of global pandemics, or could we instead become more resilient, more aware and stronger as a species?
We spoke to experts about the potential side effects of this ongoing pandemic.
How have things changed since January?
As countries scrambled to impose lockdown measures in an effort to curb the virus’ growth, scientists noticed a significant shortening of the normal flu season on a global level.
“If you look at the data published earlier in the year of over 70 countries, it’s quite clear that the combination of lockdown and people isolating at home and not going into clinics have resulted in far fewer cases of seasonal flu,” says Professor Lawrence Young, a virologist at Warwick University.
With schools across the UK closed to all pupils besides the children of key workers, infections that are generally spread between younger people, such as chickenpox, have also been reduced.
Lockdown has also led to the other infectious diseases such as German measles being “somewhat reduced”. “There are even reports in the States about the decline in sexually transmitted infections,” added Young.
Could we see short-term changes?
For people who have already been infected with Sars-CoV-2 but were asymptomatic, Young says there is no reason to believe they will be at an increased risk of other infections.
But there are concerns over the potential clinical problems of being infected with more than one virus at the same time, as Covid-19 has been seen to have a profound effect on the body’s immune system.
“There’s the issue of whether people could be co-infected,” says Young. “If you are infected with Covid-19 and influenza at the same time, that could be quite significant and problematic.”
Scientists are also unsure whether some “cross-reactivity” or “cross-protection” could occur when a person is infected with Covid-19 and another type of common cold coronavirus (in total, there are seven coronaviruses known to affect humans) and how that could impact a person’s immune system.
What about in the long-term?
Covid-19 has essentially put a large numbers of medical appointments on hold, and scientists say this could have a huge knock-on effect on people’s health in the long-term.
“A lot of things have gone under the radar or not gone on the radar at all,” says Professor Jonathan Cohen, infectious diseases expert at Brighton and Sussex Medical School. “There will be a very long catch-up period after Covid-19, and it’s sadly inevitable that some people will fall through the cracks.”
Dr Freya Jephcott, an epidemiologist at the University of Cambridge, says in the aftermath of the 2014 Ebola outbreak in West Africa, childhood infections such as measles became more common.
“Any disruption to routine vaccination is likely to see the re-emergence of common diseases,” she says. “In the case of Guinea, more people ended up dying of malaria than Ebola.”
There is a risk that viral infections such as polio – which fell dramatically once a routine vaccination was introduced in the 1950s – could become more common, says Jephcott.
Can you catch Covid-19 twice?
Our ability to build immunity to Covid-19 depends on how long the antibodies produced after having it will last.
Common vaccines such as the one against measles give a person a weakened form of a virus, which allows the body to develop an immune memory that stays with them for the rest of their lives. If that person is later exposed again to the measles virus, their body’s immune memory activates itself and the person is not infected.
The new coronavirus, Sars-CoV-2, has not been around long enough for scientists to know how long immunity will last.
In other human coronaviruses, the body’s immune memory is triggered but it doesn’t stop a person from being reinfected. The good news is that while people have been shown to catch coronaviruses more than once, they haven’t been found to fall seriously sick from them a second time around.
“As far as I can see, there are no reports anywhere in the world that anyone has been reinfected of Covid-19,” says Professor Young. “But it’s probably too soon to say.
“The hope is Covid-19 is analogous to other coronavirus infections. So the body could become susceptible to reinfection after a year or so, but the body reactivates its memory very quickly and so you don’t have any disease.”
Can Covid-19 affect how you catch other viruses?
What has been less reported is the question of whether Covid-19 can cause a so-called “reactivated infection”, where the virus impacts on an infected person’s immune system, making them more susceptible to other infections.
For example, an adult who had chickenpox as a child could see the virus “reactivated” years – perhaps even decades – later in a similar nasty condition called shingles. “There have been quite a number of cases of shingles being reported recently, possibly as a consequence of the impact of Covid-19 on the body’s immune system,” says Young.
“We just don’t know what the long term consequences of Covid-19 will be on the body’s immune response,” he admits.
“One of the most frightening things is this infection results in a variety of different effects in the body – some of them can be quite long term, as we’re only just beginning to understand. We’re already seeing reports of people with long-term lethargy and possibly some form of chronic fatigue syndrome.”
“Aside from the obvious long-term effects in terms of lung disease and lung fibrosis, it could also end up affecting the way a person responds to other infections. We just don’t know yet.”
Will social distancing help prevent other viruses?
Social distancing, the wearing of face masks and increased hand washing would have a significant long-term impact on common respiratory virus infections – provided these measures continue past this year.
The problem is many experts don’t believe people will continue much longer with these measures.
“We’re already seeing from these local outbreaks where people are not seemingly obeying social distancing rules,” says Young. “There is a frustration and a weariness to these protective measures and there is the sense among younger people that they are more protected and unlikely to get the disease.”
Dr Jephcott agrees. “People tend to get extreme fatigue with social restrictions, so there is even a risk of a celebratory rebellious reversal of practices,” she says. Here in the UK, we have also seen thousands of young people attend illegal raves over the summer.
How about future global viral outbreaks?
Scientists have for some time feared a global pandemic such as Covid-19 would eventually happen and that when it did, we would be completely unprepared for it. After all, virus outbreaks happen all the time – it’s just that they’ve been taking place in geographically restricted areas, such as Ebola in Africa, MERs in the Middle East, or SARS in East Asia.
As a matter of fact, “outbreaks are increasing and they are going to get larger,” says Dr Jephcott.
“What we’re seeing are growing human populations and density, escalating deforestation, a high level of animal farming as well as even more international travel. We are in the age of emerging infectious diseases.”
Climate change has a very clear impact on infections, as climatic conditions influence virus infections – such as in the case of malaria. The spread of viruses will also depend on how our relationship with animals changes; viruses such as influenza, HIV and coronaviruses (including Covid-19) are all zoonotic infections that are spread from animals to humans.
Young says Covid-19 has served as a “massive wake-up call” that the world cannot be complacent about clinical biological research or vaccine development. Nowhere has this been more obvious than in the UK.
“Very early on, countries like Germany were able to rapidly respond to coronavirus by developing diagnostic tests and effectively organising their public health structure,” he says. “That is because they had invested and built a better infrastructure for supporting virus research and the rapid development of new diagnostics.”
He hopes this new investment in virology and vaccine development will mean we are better able to protect ourselves from future pandemics. “We could even develop vaccines for viruses that don’t even yet exist.”
And while it is likely there will be future outbreaks of different and new types of coronavirus infections, scientists hope we will be better equipped to treat and tackle them rapidly.
Young concludes: “The hope is that this horrible situation has just made us realise that we can’t be complacent about virus infections.”