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Pubs, restaurants and cafes in England welcomed customers back through their doors on 4 July, sparking warnings of a second wave of covid-19 infections. Yet there have been warnings of another wave since the country began easing restrictions, and one hasn’t materialised. Will this time be different?

Ů��С��Ƶs on an independent advisory panel on coronavirus called Independent SAGE have repeatedly warned that the relatively swift easing of lockdown restrictions in England risks cases rising again.

On 11 May, people in England were allowed to go outside to exercise multiple times a day and certain groups were encouraged to return to work. June saw the reopening of non-essential shops, certain year groups returning to school and households mixing outside. On Saturday, social distancing guidelines were reduced and numerous indoor hospitality venues reopened.

Speaking at a press briefing last Thursday, England’s deputy chief medical officer, Jenny Harries, said a new spike in cases in the UK was a possibility: “A second peak, as in an epidemic peak, another one, is also not ruled out.”

England has eased restrictions faster than the rest of the UK and much of Europe. The government says the pace of change is justified because infections in the UK have been declining since April, when they peaked at over 8000 cases a day.

One explanation for a lack of a second wave that can be ruled out is herd immunity, whereby enough people have become invulnerable to the virus that it can no longer spread freely. The herd immunity level for this coronavirus has been estimated at 60 per cent of a population, but studies from around the world suggest that just 1 to 10 per cent of people have antibodies to the virus, which suggests a previous infection. “It doesn’t seem anything like enough of us have been exposed,” says Mark Woolhouse at the University of Edinburgh, UK. We also don’t know how long people who have antibodies are protected from reinfection.

The arrival of summer in the northern hemisphere may have helped to quash infections for now. Some evidence suggests that, as with certain other respiratory viruses, coronaviruses stay viable on surfaces for longer when the air is cooler and less humid, and some studies have found a link between new infections and lower humidity. However, it is still unclear whether the coronavirus will have a seasonal cycle like flu.

Warm weather also encourages people to spend more time outdoors, where the virus is more likely to be damaged by sunlight or drift away on  a breeze. One study in China found that 98 per cent of super-spreading events, where transmission is disproportionately high compared with normal transmission rates, happened indoors.

“Climate may or may not be a factor, but we know that spreading is less easy outdoors,” says Gabriel Scally, a member of Independent SAGE.

There may be other factors that are keeping case numbers down. Around half of UK deaths related to coronavirus have been care home residents, but such settings now have better infection control practices in place.

Another possible explanation is that people are continuing with precautionary behaviours. A poll of more than 2000 UK residents compared people’s attitudes towards lockdown rules at the start of April with those at the end of May and found compliance remained high.

“People were still sticking pretty uniformly to the social distancing measures,” says Bobby Duffy at King’s College London, who was involved in the study. “The theme is incredible caution and a strong sense of the risks involved among the majority of the population.”

It has also only been a few weeks since people really started to go out more. “It takes time to build up the cases,” says Scally. A second wave hasn’t happened yet, but that doesn’t mean those who predicted one have been proven wrong.

Several countries have had a resurgence of cases in recent weeks after easing restrictions. Israel has said it is facing a second wave after reporting almost 1000 new cases on 5 July, and has reimposed restrictions. South Korea has had several new clusters of infections, stemming from nightclubs and offices. Restrictions have also been reimposed in parts of Spain. And several US states, including Texas, have reversed the easing of restrictions in bars and restaurants.

“Virtually every place that starts to loosen up and where social distancing diminishes, you start to see outbreaks appear,” says Anthony Costello, also of Independent SAGE. “The question is, do they coalesce into a full blown second surge.”

There are hints that things could be changing in the UK. Latest figures from the Office for National Statistics show that the declining incidence rates in England seen until early June have now levelled off. There is also a local outbreak in the city of Leicester, which has gone back into lockdown.

It is vital any new clusters in the UK trigger similar local lockdowns, says Adam Kleczkowski at the University of Strathclyde in Glasgow, UK. “We are much more prepared now and we understand the dynamics of the virus more than three months ago.”

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