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By Roger Highfield on

Coronavirus: will there be a winter wave?

The UK must prepare now for a potential new wave of coronavirus infections this winter that could be more serious than the first, warned a report in July. Roger Highfield, Science Director, asks one of the authors about the state of current COVID-19 preparations.

I talk to Professor Dame Anne Johnson, Professor of Infectious Disease Epidemiology at University College London, Vice President International of the Academy of Medical Sciences (AMS), and member of an AMS Expert Advisory Group chaired by Professor Stephen Holgate which reported in July on the prospect of a winter wave to the Government Office for Science. Her edited responses are in italic.


This in part depends on immunity within the population. When a high proportion of the population has been infected by an infectious disease and achieves long-lasting immunity then rates of infection in a population may be slowed as fewer people are susceptible to infection.

But testing suggests that only five or ten percent of the UK population has so far been infected with the SARS-CoV-2 virus to date, with levels up to 15% in some areas, so the majority of people have no specific immunity to COVID-19.

There are also many uncertainties. For example, we don’t know the degree to which immunity is conferred by past infection or how long immunity lasts and whether, for instance,  some people may have a degree of cross-protective immunity from other coronaviruses such as those that cause the common cold, or even how long someone remains immune after being infected with SARS-CoV-2.


One tends to think about an outbreak as exactly that. A relatively small but containable outbreak of infection that is geographically or environmentally limited, for instance in a town, a factory, or a ship.

When it comes to a broader transmission or a  ‘second wave’, you’re  concerned about wider spread transmission of the virus throughout the community.

We talk about R, the reproduction number, which is a measure of  the average number of people infected by an infected person over the time that they are infected. It is R which determines the rate of increase or decrease in the number of COVID-19 infections.

When R is above one, the spread of COVID-19 is going to accelerate. Under one, the pandemic will decelerate.

But the number of people infected at any given time, the prevalence of infection, matters too. If you’ve got a high R number but very few people in the population infected then you have a good chance of tracking down all the cases and suppressing transmission.  

For example, you can have an outbreak that never gets beyond the walls of a care home even though the number of transmissions from a single case is high, which is awful for the care home but might not cause onwards transmission into the community.

But once R is above one and a there is a significant prevalence of infected people in the community, the number of cases can rise very rapidly due to exponential growth as we saw in March.

This dashboard shows hotspots as well as estimates of R by local authority area.


I watch the COVID-19 figures every day and we are witnessing re-emerging epidemics all over Europe (a further 2,988 cases of coronavirus have been reported in the UK in the past 24 hours, the highest number reported on a single day since 22 May and a rise of 1,175 on Saturday 5 September).

France now has as many cases as it had at the peak of its last wave but of course they – and we – are doing much more testing so finding a higher proportion of cases and spotting less-severe cases.

So, comparing like with like will be difficult because a lot of the cases diagnosed now are the milder ones in the community, rather than severe cases in hospitals.

We are not seeing the high death rates we did earlier in the year, partly because we are now diagnosing milder cases that were previously not recorded. It may also be because a different population is being infected, notably younger people, perhaps because older people are being more cautious than younger ones and because infection control has improved in hospitals and care homes.

There is also the possibility of changes in the virus but there is no evidence yet of this affecting disease severity.


When we get sustained community transmission with an R number which is well above 1, we see the kind of generalized spread of disease that we saw in the peak of the UK epidemic in March (when R was around 3).

Having said that, it was not a homogeneous epidemic, that is, one that was spread evenly. Instead, it was a heterogeneous epidemic, in other words spotty. Risk was higher in some groups and places at different times.

Now that we have done antibody testing, which can show who has been infected in the past, we know more about the high-risk locations. My worry is they are still the high-risk locations.

By high-risk locations, I am talking about care homes (as of 12 June 2020, 30% of COVID-19 fatalities in England, 28% in Wales, 46% in Scotland and 42.4% in Northern Ireland were in care homes), hospitals and minority ethnic communities, where – and we still don’t fully understand why – a combination of occupation, household structure and socioeconomic factors come into play. Patient and client facing Health and Social Care workers are also at higher risk.

The Academy report said that COVID-19 related deaths have been higher for people in Black ethnic groups (1.71 to 4.2 times higher) and Asian/South Asian groups (1.32 to 3.29 times higher) compared to White ethnic groups.

Accounting for sex, age, ethnicity, deprivation and region, people of Bangladeshi ethnicity have twice the risk of a confirmed COVID-19 related death compared to White British and Chinese/Indian/Pakistani/Other-Asian/Caribbean/Other-Black ethnicity have between 10-50% higher risk of death.


Other coronaviruses are highly seasonal, though we don’t know for sure if this will also be the case with SARS-CoV-2. We published a paper on that which shows that other coronaviruses are seasonal and these and other respiratory diseases such as flu increase in incidence in winter.

This is due to biological and environmental reasons and this is why we think it might be easier to transmit SARS-CoV-2 in winter. We close the windows and we get off our bikes and get back on trains and tubes, so there is more close contact between people. These viruses probably do a little bit better in the colder and more humid conditions at that time of year.

We were worried about all those people who crowded on to a beach in Bournemouth in May but they were outside and nobody has been able to pick up a signal from that to suggest it boosted the spread of disease in a significant way.

The AMS report outlines the factors that are likely to enhance COVID-19 transmission in winter in section 3.1.3, though their relative importance is still a matter of debate. It is not known whether those infected in the winter and spring of 2020 will be protected against reinfection, and how long such protection might last; we don’t understand the impact of protective or harmful interactions between SARS-CoV-2 and other infections (e.g. common cold coronaviruses, rhinovirus and so on); although SARS-CoV-2 does not mutate much, we don’t know the potential for it to become significantly more infectious or virulent; the effect of lockdown, or fully understand the impact of weight, vitamin D levels or whatever on the severity of disease.

NHS and social care systems typically operate at maximal capacity in winter, with bed occupancy regularly exceeding 95% in recent years. The burden on the NHS in the winter is not only affected by increased incidence of flu and other infectious diseases, but also other conditions such as asthma, chronic, obstructive pulmonary disease, ischaemic heart disease, heart attack and stroke.

As recently as in 2017/18, England and Wales experienced approximately 50,000 excess winter deaths. In the same year, there were approximately 4,800 and 1,500 excess winter deaths in Scotland and Northern Ireland.


For the Academy of Medical Sciences report we asked the team at the MRC Centre for Global Infectious Disease Analysis at  Imperial College London  to do modelling in which we assumed a ‘reasonable worst case scenario’ (remember, this is not a prediction!) where  R is 1.7, a little more than half what the R number was at the start of the pandemic in the UK.

As you know, R is now hovering perilously around 1.0 so that 1.7 would be a significant increase (the relationship between R and infections/cases is exponential, so there is a really big difference between Rs of 1.3, 1.5 and 1.7).

If R remained at 1.7, the computer models suggest you would then get a winter wave of infection, which would slowly rise, with a peak in hospital admissions and deaths of a similar magnitude to the first wave in January/February, coinciding with a period of peak demand on the NHS.

In this worst-case scenario, the estimated total number of hospital deaths (excluding care homes) between September 2020 and June 2021 would be 119,900, over double the number occurring during the first wave in spring 2020 (note these projections do not take account of recent results from the dexamethasone and hydrocortisone trials, which could substantially reduce mortality).

That is why in the report we argued that you want to get this virus suppressed as much as possible over the summer so that, in September you’re starting from the lowest possible base, and so that you don’t get to the stage where you’ve got a relatively high prevalence in the population right in the middle of winter. 

We also say in the report that there should be continued focus on reducing community transmission, enhancing infection control, improving health surveillance to prevent this winter surge.


The biggest unknown is how the how the population will behave as we go into winter. We need to find the best way to maximally suppress the virus while managing to get on with something like a normal life. What is the sweet spot?

How well will businesses keep themselves clean of virus? How well with shops control infection? How well will restaurants and cafes do it? If you have been to a pub and restaurant, as I have recently, you see that the quality of the infection control is highly variable.  

When I lecture on infectious diseases I start with a simple slide which points out that the incidence of an infectious disease results from the interaction between the biology of a virus and the behaviour of a population.   


The Academy report outlined the importance of effective policies to ensure people adopt physical distancing; wear face coverings where physical distancing is not possible; regular hand and respiratory hygiene; high levels of hygiene in the home; and self-isolation and participation in the test, trace and isolate programme.

To do this, it called for an extensive public information campaign in the autumn, co-produced and optimised by members of target communities working together with professional organisations with a local and multi-ethnic focus.

What hasn’t yet happened is an extensive public health campaign in the autumn co-produced by members of target communities. We need to get over clear, simple messages about how we have to minimise the number of people with whom we have close social contact, to physically distance from one another and when we can’t, to wear a face covering.

We really need to work with local communities and community leaders to explain what’s going on. We saw how important that was with Ebola, for example. But I have not seen enough of this in communities that have been badly affected, perhaps where English is not the first language, so that everyone knows the symptoms, how to get a test, and so on.

I think at the moment the public is pretty confused about what are the right things to do when it comes to the degree to which they mix, the number of people they mix with and the extent of infection control.

Equally, we have to get society going again.

At the end of the day, without an effective vaccine or a good treatment, the tools that we currently have are entirely behavioural and very similar as when we faced the influenza pandemic over a century ago and not dissimilar to when they tried to escape the plague 300 years ago, or when Florence Nightingale began to understand the importance of cleanliness.

I am very concerned about infection in hospitals and care homes. We are having to deal with a different kind of control of infection with COVID-19 than, for example, MRSA (an antibiotic resistant bacterium, or ‘superbug’) which care homes were more familiar with. It took too long for us to understand that washing your hands is not enough and that social distancing, masks, and PPE are all very important.

When it comes to the spread of the virus from surfaces, highly sensitive techniques can find traces of virus but whether it is viable virus is another question, along with if there is enough viable virus to set up an infection – if  you get exposed directly to a sneeze or cough full of COVID-19 infected material that may be different thing from putting you hand on a surface with a few viral particles that still has to get to the right cells to replicate.


If you look at the contact tracing data, you will see that the majority of contacts are through fellow household members. Household transmission is a very important route and if you can prevent it, that can make a big difference. 

I was at home with an infected family member for three weeks and didn’t get infected. But I was fortunate to have a spare room and extra bathroom, which I know not everybody has, so could distance from the family and eat at a distance, and ensure surfaces and so on were carefully washed. Today I would have worn a mask as well. Clearly if you are in a crowded, multi-generational house that is very difficult to do.

However, I should add that infection is not a certainty when you share a house with an infected person. In Wuhan, they found the minority of household members ended up being infected even though household transmission was the source of many cases.


In its report, the Academy called for large scale population surveys to establish how pervasive the virus is and an expansion of the Test, Trace, and Isolate (TTI) programme to cope with increasing demands over the winter.

Isolation and then testing those with symptoms is important for control but the number of people with flu-like symptoms similar to COVID-like symptoms will increase in the winter because more respiratory viruses are circulating. That means a lot more people need to be tested, and then you’ve got the problem of how to sort out who’s got flu and who’s got COVID-19.

The Academy has called for ‘multiplex’ testing, that is for both COVID and influenza (the winter of 2017/18 saw almost 50,000 excess deaths, with over one third caused by respiratory disease).

If you find who has got influenza with a quick turnaround, you can give those at high risk antiviral drugs such as Oseltamivir, sold under the brand name Tamiflu, which are most effective when used early, which has not been possible before because we did not test for flu virus.

You also have to do TTI fast if you are to stop transmission. However, one aspect of testing has been misunderstood which is that contact tracing is NOT the most important part.

We did some modelling for the Royal Society Delve (Data Evaluation and Learning for Viral Epidemics) group on Test, Trace and Isolation and argued that test, trace and isolate, is a ‘leaky pipeline’.

A large fraction (40 per cent or more) of infected people have no symptoms, so you won’t catch everyone who is infected. So that is one leak. Then you don’t always get their contacts, which is another. Not everyone will agree to be tested, and so on.

So, when we took account of all these leaks in the system, we found that even if you do TTI really well, you only reduce transmission by up to 15%.

It is still worth doing and could push R below 1 but the biggest impact comes from people who feel sick or unwell self-isolating immediately, so that they don’t pass the virus on any further.

They can then get tested and avoid passing anything on while they await results. In other words, contact tracing is a welcome but smaller benefit and isolation of suspected cases is the most important.


Our knowledge that other coronaviruses are seasonal would suggest there is a lower instance of respiratory disease in the summer but it is complicated – for example, we have seen significant COVID-19 outbreaks in the United States this summer.

When you look at the southern hemisphere, where countries have gone into their winter in advance of us, it is not clear either.

Australia and New Zealand both reacted quickly to the threat from COVID-19 and managed to keep virus transmission to low levels. But there has been a terrible epidemic in South America going into winter.

So, we don’t really know how seasonal this is and we still have a highly susceptible population.

Our report said that Chile is perhaps the most relevant comparator, in terms of economic conditions and ongoing transmissions at the onset of winter:  there, cumulative confirmed cases have more than doubled in the month of June.

It has been reassuring that the seasonal influenza does not seem so bad this year in the southern hemisphere, probably as a result of measures taken to curb COVID-19, but what happens in the southern hemisphere doesn’t always predict the impact of a given flu strain in the northern hemisphere and if we get a bigger second wave of COVID-19 we will have the circumstances which would also allow influenza to transmit.

That is why we need plenty of influenza vaccination.


We still don’t understand the full clinical spectrum of what some call ‘long covid’. It will be very important to understand the long-term impact on lung health, along with post COVID-19 heart attacks and strokes because of clotting issues. It is incredibly important we monitor this.

But there is also an indirect ‘long covid’ which is the damage we are doing in terms of undiagnosed, untreated cancers, mental health problems, the effects on young people, unemployment and so on.

We do have to be careful that the treatment isn’t worse than the disease.  We must take care not to damage a generation.

The Academy report was emphatic that we have to work off the backlog of NHS work such as non COVID-19 treatments, cancer screening, and vaccination.

Recent estimates suggest that the overall waiting list could increase from 4.2 million (pre COVID-19) to approximately 10 million by the end of the year in England alone.


Clearly there are several vaccines being tested which use different approaches to create immunity (for example, so called RNA vaccines).

However, we don’t know whether any immunity resulting from these vaccines will be long lasting or whether they may only protect from severe disease but still allow you to become infected. 

We will have to wait for trials to be completed to see how well each vaccine works. Even then, you have to manufacture millions of doses, decide who to give it to, then get these people immunized. Even if we had a proven effective vaccine having any impact over any winter or a second wave is over optimistic because of these logistical challenges alone.  


Back in February we were perhaps thinking too much about COVID-19 being like a flu pandemic and that once community transmission was firmly established, control would be very difficult. With hindsight, we should probably have done more to identify levels of infection and suppress the virus.

We also know there were lots of infections earlier than we realised and some in Europe that may have dated back to December. What often happens with new infections is that one or two isolated infections come into a community but do not spread, like sparks that don’t set off a fire. That may have happened multiple times before the epidemic took hold in the UK.

We know we had multiple introductions of COVID-19 from all over Europe, more than other European countries. We had little testing capacity and didn’t understand the extent of asymptomatic infection and had insufficient PPE.

We’ve had a lot of transmission in highly vulnerable populations, especially care homes which was not helped by discharging patients who had not been tested into care homes to protect the NHS. I also worry about the amount of transmission that occurred in hospitals and among health and social care staff.

From March, a high fraction of the deaths were due to infections occurring in care homes and transmission occurring in hospitals. So, if you work very hard to minimise hospital and care home infections and if the elderly and those at higher risk naturally shield, which I think many are doing, then that also pushes down the death rate, even if there are more infections occurring in younger people, who have much lower risks of severe disease.


The latest picture of how far the pandemic has spread can be seen on the Johns Hopkins Coronavirus Resource Center or Robert Koch-Institute website.

You can check the number of UK COVID-19 lab-confirmed cases and deaths along with figures from the Office of National Statistics.

There is much more information in our Coronavirus blog series (including in German by focusTerra, ETH Zürich, with additional information on Switzerland), from the UKRI, the EUUS Centers for Disease ControlWHO, on this COVID-19 portal and Our World in Data.

The Science Museum Group is also collecting objects and ephemera to document this health emergency for future generations.