Coronavirus cases could re-surge as lockdown lifts - here's why

The government's decision to slightly relax lockdown rules has lead some to wonder whether a second coronavirus wave could hit the UK as a result.

It was the second wave of Spanish flu that killed more people than the first, and many fear that history may repeat itself with Covid-19.

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Most experts agree that a rise in cases is inevitable as lockdown eases, given that there is currently no vaccine available and cases have not been entirely eliminated in the UK. In countries where lockdown restrictions have begun to ease - such as Germany - cases have started creeping up again.

The severity, scale and ability to manage a second wave of the virus is difficult to predict ahead of time, but it does depend on a few key factors.

Individual behaviour

While some will take the government's relaxation of rules as licence to bend the rules of social distancing, others will remain nervous of changing their behaviour while the disease is still present in the UK.

Some doctors have warned that a lack of clarity on the current rules could cause the population to ignore social distancing, thus causing a huge spike in infections.

How the UK responds to the relaxation of rules will therefore hugely affect the size of the second wave - and is currently difficult to predict.

Immunity

Without a high level of immunity against coronavirus in the population, many are still susceptible to becoming infected.

Thomas House, a reader in statistics at the University of Manchester who is modelling the current epidemic, told Wired that, while lockdown measures may have flattened the curve, it's left much of the UK population susceptible.

“The bad news seems to be that where people have tried to look in the community and other places there hasn't been a tremendously high level of acquisition of immunity. That means it doesn't look like we can come straight out of lockdown and back to normal," House said.

Until a high level of immunity is achieved among the population or a vaccine found, therefore, a re-surge in cases is difficult to prevent as lockdown measures ease.

Contact tracing and testing

The key to keeping coronavirus infections low, as with the first wave, is to aggressively test, isolate and contact trace.

Testing allows countries to identify and isolate cases of coronavirus, preventing the virus from spreading further.

Contact tracing involves getting in touch with everyone who was in contact with a confirmed case, allowing them to also isolate and stop the spread of disease. Countries like South Korea, where an aggressive approach to testing and contact tracing was taken, have had much lower infection and death rates from coronavirus.

International travel

The UK recently introduced a mandatory 14 day quarantine period for international travellers, but once this lifts or relaxes, international travel could affect case numbers.

Until the pandemic is over globally, imported cases may continue to affect coronavirus case levels in countries around the world.