It’s been five years since the start of the Covid pandemic. Although most of the government mandates, from social distancing to face masks, have been consigned to the past, the virus is still prevalent – and capable of causing real harm.

Although it was initially forecast to become a seasonal illness, the virus is on the rise in the US – making it far from the common-cold-style winter illness that was expected.

Experts said a lot of predictions made about how Covid-19 would evolve have turned out to be wrong. Five years on, what do we know about the virus?

Is Covid on the rise?

Although news of a summer wave in the US has led to fears it could be replicated in the UK, the latest data from the UK Health Security Agency (UKHSA) shows that cases dropped by 28% over the past week to reach 1,046. Since most people don’t test any more, this is unlikely to reflect the true prevalence. The data for the past year shows levels have remained consistent, with a large spike last October.

Is it a seasonal illness?

Experts assumed that as Covid became endemic, it would change into a winter bug, like the common cold or flu. UKHSA stats show this is not the case. “It is absolutely true that you are as likely to get Covid in summer as in winter,” said Danny Altmann, an immunologist at Imperial College London.

He added: “It’s been a shifting discussion – when do we calm down and say it’s become an endemic coronavirus like the common cold. I think we’re still so far off that place. There’s a kind of optimism that it’s just a winter sniffle, but it’s not a sniffle; it’s quite symptomatic, especially in vulnerable people and in the excess death figures, and also it is absolutely not seasonal.”

Altmann said that, although there is a perception that, as a coronavirus, Covid-19 is akin to a common cold, in reality it is closer to the flu in terms of the death rate, its impact on the NHS and the potential severity of symptoms.

Simon Williams, a sociologist at Swansea University who has researched public views on the pandemic, said: “We’re getting to the point where there’s a legitimate question about whether it will ever be [a winter virus]. It’s not a typical respiratory virus in terms of seasonality.”

Adam Kucharski, a professor at the London School of Hygiene & Tropical Medicine, said that because Covid-19 evolves quickly – twice as fast as the fastest flu – it is less constrained by season. “Whereas a small change in transmissibility conditions is enough to stop flu in summer, Sars-CoV-2 can basically evolve its way over this barrier,” he said.

Which variant are we on now?

The main Covid viruses in circulation are the Omicron subvariants. These are “obviously milder than Wuhan or Delta”, Altmann said, adding it’s not the case that they are becoming progressively milder, but rather population immunity is higher owing to vaccines and prior infections.

The newest variant, NB.1.8.1, has been detected in the UK and international data suggests it is growing as a proportion of all Covid cases. World Health Organization analysis found the new strain is more contagious, but vaccination gives significant protection.

Williams said we can expect to keep seeing the virus evolve, similar to how there are new flu virus combinations each year.

Should we all get vaccines?

The experts agreed the main problem is the low take-up of the free vaccine, which is available to people at greatest risk from Covid infection, including those aged 75 and over and those who are immunocompromised.

Altmann said anyone who could afford it may wish to pay for the vaccine – not least because he hears regularly from new long Covid sufferers: “Who wouldn’t feel safer with boosted neutralising antibodies and T-cells?”

He noted there is a spectrum of suffering, with people who are infected occasionally and mildly or non-symptomatically on one end, and on the other, those living with long Covid. There is also a third, under-researched, group in the middle of young or middle-aged people who get four to six reinfections each year, and may have to take several days off work each time. “It’s non-trivial and makes it quite hard to do your work,” he said.

Although there is still hybrid immunity in the population because most people received several vaccines during the pandemic, there is a growing population of children who would have been too young to have received them at the time.

The experts feared that growing vaccine hesitancy, which Williams described as “one of the most pressing concerns” in public health, could have an impact on whether these children receive a jab or people turn up for their boosters.

Another consideration, when it comes to building immunity, is the growing body of research suggesting that for several months after a Covid infection, people become more vulnerable to other infections and there can be lingering effects on the heart, cardiovascular system and the brain.

“We’re only five years into this virus, there’s a lot of question marks and unknowns,” said Williams.