The reproduction number (R) is the average number of secondary infections produced by 1 infected person.

The Scientific Pandemic Influenza Group on Modelling (SPI-M), a sub-group of the Scientific Advisory Group for Emergencies (SAGE), has built a consensus on the value of R based on expert scientific advice from multiple academic groups. This has been reviewed by SAGE.

The range of 0.7-1.0 is an estimate based on latest data available to determine infection and transmission rates. Data such as contacts, hospital admissions, ICU admissions and deaths generally takes 2 to 3 weeks for changes in R to be reflected in these data sources, due to the time between infection and needing hospital care.

As data on infection is estimated through data on symptomatic cases, hospitalisations, or deaths, there is a delay of around 2 to 3 weeks because as there is a lag between people between people becoming infected, entering hospital, and dying. Consequently, this range applies to data before the recent adjustments to the restrictions the government has put in place earlier this week.

An R number of 1 means that on average every person who is infected will infect 1 other person, meaning the total number of new infections is stable. If R is 2, on average, each infected person infects 2 more people. If R is 0.5 then on average for each 2 infected people, there will be only 1 new infection. If R is greater than 1 the epidemic is generally seen to be growing, if R is less than 1 the epidemic is shrinking.

SAGE is confident that overall the R is not above 1. This means that the number of infections is not increasing, and is very likely to be decreasing.

R can change over time. For example, it falls when there is a reduction in the number of contacts between people, which reduces transmission.

In the coming weeks and months, the R number will be updated every week on the GO-Science website.

Sir Patrick Vallance, Government Chief Scientific Adviser said:

R is one of the most important things you can track to understand an epidemic. If you can estimate R, then you have part of a reliable tool for planning how to combat the virus.

If the R is higher than 1 that means this disease is growing exponentially and will keep on spreading to more and more people. To keep R below one and control the virus, it is vital that people stay alert and continue to follow the latest government guidelines to the letter.

In the coming weeks we will update this estimate regularly.

R is not the only important measure of the epidemic. R indicates whether the epidemic is getting bigger or smaller but not how large it is. The number of people currently infected with COVID-19 – and so able to pass it on – is very important. It is estimated by ONS and available on their website. ONS will publish this figure regularly, so as to enable tracking of whether it is going up or down.

R should always be considered alongside the number of people currently infected. If R equals 1 with 100,000 people currently infected, it is a very different situation to R equals 1 with 1,000 people currently infected.

Limitations of R

R is an average value that can vary in different parts of the country, communities, and subsections of the population. It cannot be measured directly so there is always some uncertainty around its exact value.

How is R estimated?

Individual modelling groups use a range of data to estimate R including:

• epidemiological data such as hospital admissions, ICU admissions and deaths – it generally takes 2 to 3 weeks for changes in R to be reflected in these data sources, due to the time between infection and needing hospital care
• contact pattern surveys that gather information on behaviour – these can be quicker (with a lag of around a week) but can be open to bias as they often rely on self-reported behaviour
• household infection surveys where blood samples and swabs are performed on individuals which can provide estimates of how many people are infected – longitudinal surveys (which sample the same people repeatedly) allow a direct estimate of the infection rates

Different modelling groups use different data sources to estimate R using complex mathematical models that simulate the spread of infections. Some may even use all these sources of information to adjust their models to better reflect the real-world situation. There is uncertainty in all these data sources, which is why R estimates can vary between different models, and why we do not rely on one model; evidence is considered, discussed and R is presented as a range.

Who estimates R?

R is estimated by a range of independent modelling groups based in universities and Public Health England (PHE). The modelling groups present their individual R estimates to the Science Pandemic Influenza Modelling group (SPI-M) – a subgroup of SAGE – for discussion. Attendees compare the different estimates of R and SPI- M collectively agrees a range which R is very likely to be within.

Thank you very much Director-General for your summary and to the chairs of the negotiating groups for their updates.

I wanted to start by joining you, New Zealand Ambassador David Walker, and others in paying tribute to Mike Moore. He was the nearest thing we have had to a British Director-General for a long time, and we in the United Kingdom are very proud of him, and of his legacy here in the World Trade Organization.

With the kind permission of the Chair of the General Council, my Secretary of State for International Trade will be here to address the General Council tomorrow, and so I will keep my remarks today brief.

As Members will be aware, the United Kingdom has circulated a document contained in WT/GC/206, which sets out some of the implications of our departure from the European Union. I would like to take this opportunity to thank all Members, as well as you and your team in the WTO Secretariat, for all of the constructive support we have received in this process.

I would now like to say a few words about the United Kingdom’s approach to the ongoing negotiations in which we are all engaged, and our ambitions for 2020 and beyond.

We agree with you, Director-General, that success at MC12 will be measured by the substance of what we agree. And as others have said, starting with the Swiss Ambassador Didier Chambovey, the principal metric of that success will be whether there is a fisheries deal, one that leads to meaningful reductions in harmful subsidies. The Chair, Ambassador Wills, set out the challenges and the way forward, and we agree with him. We need to move to a consolidated text by mid-March. Members need to examine their own long-held positions critically, exercise restraint, and rally around compromises instead of sticking to incompatible national positions. The dire conditions of many of the world’s fish stocks dramatically highlights the need to deliver on this Sustainable Development Goal target. We stand ready in the UK, as do our ministers, to help the Chair and you get a deal across the line at Nur Sultan.

More broadly, as upcoming COP26 hosts, we warmly welcome other discussions in this House aimed at facilitating green growth and a more sustainable global economy.

On agriculture, I wanted to thank Ambassador John Deep Ford for his detailed report. The United Kingdom is committed to a fair and market orientated agricultural trading system, and we look forward to working with Members to address the challenges that we face and progress negotiations. We know how important this issue is for so many Members of this House.

Regarding your second tranche of issues for MC12, the United Kingdom has long supported the Joint Initiatives. They represent perhaps the most significant reform to the WTO in recent years. If they succeed, these initiatives will advance digital trade and trade in services, open up new opportunities for Micro, Small and Medium Size Enterprises, and facilitate global investment for development. But, in addition to that, they will strengthen the negotiating function of the WTO, upon which the health of the global trading system depends.

On wider WTO reform, the United Kingdom supports efforts to strengthen the rules on subsidies, we support efforts to improve compliance around transparency and notifications, and we do need to discuss questions around non-market policies and practices. The WTO cannot afford to ignore these issues.

Finally, allow me to turn to the dispute settlement system. We view a fully-functioning, compulsory, binding and impartial system, with two-tier review as crucial to ensure the rules that we have negotiated can be enforced. We are committed to finding solutions that all Members can support in order to reinstate a fully effective dispute settlement system.

By way of closing, Director-General, let me just reiterate that the United Kingdom stands ready to help, in any way you would find useful, to achieve a meaningful outcome at Nur Sultan that both reconfirms the WTO’s central role, and opens up new opportunities and prosperity for our businesses and citizens.