Five years ago this month, the first patients started arriving in hospitals in Wuhan, China, with a mysterious kind of pneumonia. Covid-19 had arrived and the world would never be the same.
Covid was described as a “public health emergency of international concern” by the World Health Organization in January 2020. The emergency’s end was declared in 2023. Although people are still catching Covid – and some get very sick – most are advised by the NHS to treat it like other respiratory diseases, such as flu and colds.
We know a lot more about Covid now than we did five years ago, having quickly developed vaccines and treatments. But there are still questions that divide the experts, such as the virus’s origins, its effects, and how we should respond to it. Many of them have implications for future pandemics – so what does the science say?
Where did the Covid virus come from?
Early on, it seemed clear that the virus had spread from animals to people at a large market in Wuhan.
Many of the first people to get infected worked at the market or had links to it. And a few of the market stalls also sold live wild animals, including racoon dogs and palm civets, which are possible animal hosts for this virus.
But the nearby Wuhan Institute of Virology had been studying other viruses in the coronavirus family for the past decade, raising suspicions this was the real source. Some people have even speculated that this lab deliberately engineered the Covid virus.
The last claim has few serious advocates. Virologists have been poring over the genetic sequence of this virus since January 2020; if it weren’t a completely natural virus, it would be obvious.
But Covid could have leaked from the Wuhan lab accidentally, for instance, if a worker got infected and passed it on. They might not have even noticed.
The market origin theory has more adherents, with the lab leak idea having sometimes been painted as a conspiracy theory. Yet it has some serious proponents, including the head of the FBI.
We may never find out the truth. The Wuhan market was shut down on 1 January 2020, emptied of stock and deep-cleaned. China has denied the Wuhan Institute of Virology was studying the specific Covid virus itself.
“We cannot know and it’s frustrating,” says Professor Mark Woolhouse, an infectious diseases expert at the University of Edinburgh.
Do lockdowns work?
The UK had three national lockdowns in the pandemic. If at all possible, people had to stay at home, leaving only for essential shopping, medical reasons, or up to an hour of exercise.
Lockdowns were judged necessary to stop the potentially deadly new virus from spreading, but they also had downsides for people’s mental and physical health and stopped many people from going to work. Could they have done more harm than good?
Lockdowns clearly do “work”, in that Covid cases started falling after each one began. But they cannot last forever. Given that the virus eventually infected the majority of people – with 7 in 10 having had covid at least once by February 2022, according to Office for National Statistics estimates – it could be argued that lockdowns only delay the inevitable.
On the other hand, lockdowns did stop too many people catching Covid at once, which could have overwhelmed hospitals. They also succeeded in delaying when most people caught Covid until 2021, after they had been vaccinated, and the jabs cut risk of severe illness and death, even though people can still be infected.
Sweden is often cited as a country that didn’t lock down. In fact, it did introduce some Covid restrictions, but they were often just advisory. Notably, schools stayed open, apart from those for sixth formers.
As judged by the rate of excess deaths – which includes those from Covid and other conditions, Sweden did better than nearly every other developed country, according to an analysis by The Spectator using Office for National Statistics methods. Given there is now so much concern about children’s mental health and education loss, it would seem galling if closing schools was not a necessary part of lockdown.
We will see the impact of the pandemic on our wellbeing for years, especially on schoolchildren, said Professor Adam Kleczkowski, a mathematical biologist at the University of Strathclyde. “A lot of people say it’s all due to Covid, another group says it’s all due to lockdowns. I think it’s both.”
Do facemasks work?
At the beginning of the pandemic, health officials told the public not to bother wearing face masks, unless they had Covid symptoms, saying the evidence that they would help is marginal. The World Health Organization had similar advice.
By May 2020, the UK public was now told face coverings were obligatory, and the blue “medical masks” became ubiquitous.
The U-turn happened because scientists couldn’t agree on whether face coverings had much effect. Nearly five years on, they are still fighting over it.
Face coverings may seem like a no-brainer. Imagine someone coughing out droplets laden with coronavirus. A mask over the mouth stops them from being spewed into the air. A mask worn by someone else nearby might stop them being inhaled.
But there are several reasons why this might not make much difference to infection rates. One is that, as well as being directly coughed out in large droplets, viruses can also float in the air in smaller droplets that can pass through the gaps between mask and face when people breathe in.
Plus, people often wear badly fitting masks or pull them down sometimes for fresh air. So even if a mask reduces your exposure to the virus somewhat, if there’s enough virus in the air, that could be enough to infect you during a certain period – while on public transport, say.
Only randomised trials can tell us how masks affect infection rates in real life. The few that have been done suggest masks do have an effect, but it is modest – for instance, in one recent trial, wearing a mask in public for two weeks cut those getting respiratory illness symptoms from 12 to 9 per cent.
The next question becomes whether that size of effect is worth the inconvenience for the individual. And that’s a subjective issue.
Who needs booster vaccines?
This year, the NHS offered Covid boosters only to people who are either 65 and over, live in care homes or are in high-risk groups.
This is a much smaller fraction of the population than initially, when the Covid vaccines were rolled out widely and anyone over five could get immunised. The US still offers the jab to children and babies as young as six months.
The difference illustrates how much vaccine experts in different countries disagree over the size of the threat from Covid.
Those who push more Covid-cautious policies – like the campaign group, Independent Sage (Independent Scientific Advisory Group for Emergencies) – have long lobbied for the UK to offer vaccines to all. “The more we vaccinate, the more we can try and keep up with the evolution of this virus,” said Professor Steve Griffin, a virologist at the University of Leeds, who is head of Independent Sage.
The explanation for the UK policy is that it aims to reduce hospitalisations and deaths from Covid, which young and middle-aged people are less likely to experience. “The focus of the programme is on offering vaccination to those most likely to directly benefit… particularly those with underlying health conditions that increase their risk of hospitalisation,” the Joint Committee on Vaccination and Immunisation has said.
This strategy is the more common one globally. It is broadly adopted by most countries in Europe, and the World Health Organization, although Canada takes the US approach.
This strategy fails to consider that vaccination also lowers people’s chances of getting long Covid, said Professor Griffin. But how much of a threat is posed by this condition is yet another area of contention.
How big a risk is long Covid?
Of all the questions about Covid, some are most concerned by those over long Covid – when people have lingering symptoms for more than 12 weeks.
A key question is how common it is, with some of the earlier studies suggesting alarmingly high figures. One source of confusion is that long Covid is used as an umbrella term for people who have had different experiences of the initial infection. The term includes people who got so sick from Covid they needed weeks on a ventilator in hospital – who would be expected to take a long time to recover – as well as people who had a flu-like illness.
Even when just considering those who were not hospitalised, another pitfall is that some early studies surveyed only people who had been infected, on symptoms such as fatigue. But it is very common for people to have fatigue whether or not they’ve had Covid. Better-designed studies that compared symptom rates in people who were infected versus those uninfected give lower prevalence figures, typically of around a few per cent.
But giving a single figure for the prevalence of long Covid can also be misleading, as the term encompasses a wide spectrum of symptoms of varying impact.
The long Covid symptoms that get the most attention are fatigue and breathlessness, with media coverage focusing on people who are most severely affected, such as those who are left unable to work or are even bed-bound. In fact, the long-lasting symptom most clearly linked with Covid after a mild initial infection is loss of smell and taste, according to a large Israeli study.
Another reason for optimism is that long Covid rates have been falling over time. Fewer people reported long-lasting symptoms as the pandemic went on, probably because they developed partial immunity to the virus, and the Omicron variants, which arrived at the end of 2021, may also be less virulent.
Research is ongoing to find out how common it is for someone to get lasting illness after a mild Covid infection in 2024, when most have partial immunity by now from vaccination and past infections. As more studies are done, they will add to the picture – but probably won’t stop the arguments.
