It is impossible to know whether the UK's coronavirus outbreak will get worse this winter, according to researchers.
Concerns are growing that Britain will be hit by a second wave of Covid-19 when the weather turns colder and that the current drop in infections and deaths is merely a reprieve.
Matt Hancock, along with the Government's top scientific advisers, have warned a second national lockdown could be necessary to control the coronavirus. The Health Secretary yesterday said his current priority is 'preparing for winter'.
Many scientists predict the coronavirus will act in a similar fashion to colds and the flu and become problematic when the weather is cold and people spend more time indoors, because people are closer together and more likely to spread it.
But the data we have so far is not enough to prove this will be the case, according to Oxford University scientists. The virus — scientifically called SARS-CoV-2 — is still shrouded in mystery and has only been known to science for six months.
They argue that hot countries have been badly hit by Covid-19, suggesting it is not significantly weakened by heat, and also that worse weather outdoors could make more people get tested because they're more likely to get coughs and colds.
And this could, therefore, lead to more false positive results and mean more people test positive — even though the virus is not actually more prevalent in society, the scientists claimed.
The study comes just a day after other research, involving King's College London, linked a 1°C increase in temperature to a 15 per cent decline in deaths caused by the coronavirus, adding to concerns that a second wave will emerge in the winter.
Dr Francois Cohen, from Oxford's Smith School of Enterprise and Environment, said: 'Our study found several problems with trying to understand the influence of weather using existing data on confirmed Covid-19 cases...
'The existing data can't reliably tell us whether warmer weather slows down the spread of Covid-19, as some earlier studies have tried to suggest.
'So we urge both policy makers and the public to act with caution.'
Dr Cohen and his colleagues said any analysis that has been done of how seasons affect the virus so far have been affected by the quality of testing.
At the start of the pandemic, tests were not widely available in many countries, meaning many cases were missed and there was no real understanding of the true scale of the crisis.
And many tests were not high quality, they said, meaning results were more likely to be wrong.
This means it is difficult to tell with any certainty how the transmission of the virus has changed over the past six months, they said, and current data is not good enough to tell whether seasons have had an effect on transmission yet.
In addition to this, the virus has spread all over the world and not been contained only to cooler countries.
Many hot countries have suffered devastating outbreaks and continue to do so.
Cases in Brazil have spiked from 1.6million to 2.1million in just two weeks, while India has seen its outbreak grow by 900,000 cases, from 720,000 to 1.6m in the same time, World Health Organization data shows.
Dr Anant Jani, an author of the study, said: 'Although we still don’t know the influence of weather on the spread of Covid-19, we are sure of one thing: the virus has been able to spread everywhere, including in very warm areas of the globe, such as Ecuador, Brazil and India.
'It continues to spread even in warmer states in the US like Florida, California and Texas.
'Good weather is no excuse to take risks with a disease that has already killed hundreds of thousands of people.'
Considering how the virus would be tracked in the coming months, Dr Jani and colleagues were concerned that swab testing - which is currently the only measure of the disease's spread - will be affected by the weather outdoors.
In colder weather, more people would get symptoms of illnesses similar to Covid-19 - such as colds and flu - but not actually the coronavirus, they said.
As a result, more people would get tested for coronavirus, which would lead to more false positive results.
Swab tests do not have perfect accuracy - although it is unclear how many false positive results they produce - meaning some people get told they have Covid-19 when they don't, while others are told they don't have it when they do.
Dr Cohen's paper said: 'There have been numerous concerns regarding the accuracy of the Covid-19 tests performed so far...
'False-negative results would imply that the number of confirmed Covid-19 cases is underestimated. False-positive results would imply that people who do not have Covid-19 are included in the number of confirmed Covid-19 cases.
'Concerns regarding test accuracy create an additional problem of measurement that might affect statistical analyses.'
The study was published in the journal Environmental and Resource Economics.
The study comes after scientists from around the world yesterday published a study claiming that the death rates and likelihood of severe Covid-19 increase in colder weather.
Researchers tracked the pandemic in seven countries and found a 1°C increase in temperature was linked to a 15 per cent decline in deaths caused by the coronavirus.
Professor Tim Spector, a King's College London epidemiologist who runs the Covid Symptom Tracker app and led the study, said the results suggested summer was a 'window of opportunity' to run the virus out of Europe.
People appear to be less susceptible to severe disease when weather is warmer and more humid, he said, and more in danger when it's cold outside.
This was a 'particular worry' for Britain because thousands of people are still getting infected every day and the end of summer is already approaching, Professor Spector said.
Scientists have repeatedly warned about the dangers of cold weather returning with coronavirus still circulating, because many other viruses - such as colds and flu - are much worse in the winter months.
Cells lining the airways are less resilient in the cold, experts say, and people spend more time indoors which increases the risk of the virus spreading because they are closer together and touch more of the same surfaces.
Speaking on BBC Radio 4 on Tuesday morning, Professor Spector said: 'In Europe, where we had seven hospitals recording data and temperatures and time, we saw that for every degree of centigrade increase we saw a reduction in mortality of about 15 per cent.
'So generally, as the weather got warmer the severity of the disease reduced and mortality reduced over time.
'And the same was not true in the Chinese data that we've got which was running from December to February when the temperature wasn't heating up.'
Professor Spector also looked at data from 37,000 people using the app he is running in the UK, and found people appear to be having shorter, less severe illness now that the weather is warm.
He worked with scientists around the world looking at data from nearly 7,000 patients admitted to hospital with Covid-19 in Croatia, Spain, Italy, Finland, Poland, Germany, the UK and China.
While death rates and severe disease — measured by intensive care admissions — fell as Europe warmed up, they did not change in China where most cases happened in winter.
The study found that the strongest association was found in Barcelona, Spain, where the odds of dying fell by 4.1 per cent per day between March 2 and May 19.
Overall, the hospitals in Europe saw that the need for intensive care fell by 2.2 per cent per day between late February and late May.
And the need for patients to be moved onto ventilators fell by 2.1 per cent per day.
Meanwhile, no change had been observed over a similar time frame in Zhenjiang in China - between January 17 and 21 March.
The researchers did not give a breakdown of exact numbers for how many people were being hospitalised and dying over time.
They said the weakening of the disease appeared too big to be explained purely by better treatments.
They also noted that hot, humid countries in East Asia which had seen outbreaks of Covid-19 had not had death tolls as devastating as those seen in cooler Europe.
In Indonesia, for example, there have been 86,521 cases and 4,143 deaths — a rate of 4.8 per cent, compared to a death rate of 15.4 per cent in the UK.
In Singapore there have been 47,913 cases and 27 deaths (0.06 per cent), according to the World Health Organization, and in Japan 25,096 cases and 985 deaths (4 per cent).
Spain's death rate has been 11 per cent, according to WHO data, and Italy's 14 per cent.
This may have been because Asian countries were better prepared - they generally had faster testing and a better understanding of the disease because of the SARS outbreak 18 years ago - but researchers suspect the weather played a part, too.
This article has been adapted from its original source.
© Associated Newspapers Ltd.