How Fast Is Omicron Spreading?
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Our previous article explains why Omicron can spread so fast (Yiu, 2022), this article continues to discuss how fast is Omicron spreading.
The scientific community usually uses the R number to measure the transmission rate of the virus. “Angelique Coetzee, the chair of the South African Medical Association, said Omicron’s R number, measuring its ability to spread, was believed to be above 6. The R number for Delta, the dominant variant globally, is estimated to be above 5.” (Beaumont, 2021)
The R number can be understood as a transmission multiple, say R=6 means that 100 people can infect 600 people with the Omicron variant, who may continue to infect 3,600 people. However, this R number is not commonly used in daily conversations as it is difficult for ordinary people to imagine the actual spreading speed of the pandemic from the R number.
This article therefore attempts to describe the spreading speed of the Omicron variant in the real world by comparing the daily number of newly confirmed cases (smoothed) and their daily growth rates from November 1, 2021 to January 5, 2022 in South Africa, the United Kingdom and the United States.
It has to be noted that this method would underestimate the transmissibility of the variant, because many infections can be asymptomatic without being diagnosed, and some other variants with lower transmissibility are also spreading during the same period, so the following data analysis on the spreading speed of the Omicron variant is likely to be underestimating.
Omicron spreads in South Africa
South Africa was the first country in the world to discover the Omicron variant. At that time, it was not named as Omicron, but B.1.1.529 as firstly published in the Nature Journal on November 26, 2021 (Yiu, 2021a).
The medical researcher found that the Omicron variant’s transmission power was strong. Figure 1 shows the daily number of newly confirmed cases (smoothed) and its daily growth rate in South Africa from November 1, 2021 to January 5, 2022.
There were only 264 confirmed cases per day on average in the first half month of November (1–15 November), but since November 17 the number has started increasing to a double-digit daily growth rate. On November 24, 25, there were 1,275 and 2,465 cases, implying a daily growth rate of 93%, and the smoothed daily growth rate was as high as 41%.
It took a full month to stop the number of newly confirmed cases from increasing. The peak figure was 23,437 cases on December 17. In other words, it has increased by 86.7 times (from 264 to 23,437 cases) in one month time!
Fortunately, the situation has then continued to improve, and the number of newly confirmed cases has continued to decline since December 17. The latest number of newly confirmed cases (smoothed) on January 5 was 8,734.
Omicron spreads in the UK
The Omicron variant was spread from South Africa to the UK. The daily number of newly confirmed cases has now risen above 180,000. Figure 2 shows the UK situation since November 1, 2021.
Before the outbreak of the Omicron variant, there were about 39,208 newly confirmed cases on average in the UK, but it began to surge on December 15. The number of confirmed cases on December 14 and 15 were 59,746 and 77,966, that was an increase of 30%, or an increase of 7% of the smoothed series.
The latest number of confirmed cases (smoothed) on January 5, 2022 is 182,890, which is about 4 times higher than the average in November. But the number of newly confirmed cases is still increasing.
Omicron spreads in the US
The outbreak of the Omicron variant in the United States has resulted in more than one million confirmed cases in a single day, which is a global record so far. The situation is more severe than that in the United Kingdom. The daily number of newly confirmed cases (smoothed) has risen to almost 600,000. Figure 3 shows the daily number of new confirmed cases (smoothed) and their daily growth rate in the United States from November 1, 2021 to January 5, 2022.
Before the outbreak of the Omicron variant in the US, the daily average number of newly confirmed cases in November was about 85,045, but it began to increase after Christmas. For example, the number of confirmed cases on December 26 and 27 were 198,723 and 241,901, that is an increase of 22%.
On January 3, there was a record-breaking 1,171,378 cases, a single-day increase of 372%! After smoothing, there were still 492,963 cases, that is an increase of 22%. The latest number of newly confirmed cases (smoothed) on January 5, 2022 is as high as 574,507, which is more than 6 times higher than the average before the outbreak of the Omicron variant.
Daily Growth Rate
With reference to the period from the Omicron outbreak to the peak in South Africa, from November 17 to December 17, it took about one month to increase from 264 cases to 23,437 cases, an increase of 86.7 times. It is equivalent to a continuous constant daily growth rate of 15.3% (Yiu, 2021b).
The scenarios of Omicron outbreaks in the above three countries reveal the strength of the transmission power of the Omicron variant in the orders of magnitude of 10,000, 100,000, and 1 million cases per day. We can refer to their experiences to estimate the spreading speed of the Omicron variant in your cities. As the Omicron variant can spread fast, it is almost impossible to achieve the “zero case policy”, fortunately it has been found to be less severe than the Delta variant (Yiu, 2022).
References:
Beaumont, P. (2021) Omicron driving record rate of Covid infection in South African province, The Guardian, December 3, https://www.theguardian.com/world/2021/dec/03/omicron-covid-variant-record -rate-of-infection-south-africa-gauteng
Our World in Data (2022) Coronavirus (COVID-19) Cases, Statistics and Research. Available online at https://ourworldindata.org/covid-cases. Accessed on January 7.
Yiu, C.Y. (2022) Why is Omicron’s severe rate lower? Checkered, Jan. 5. https://vocus.cc/eyanalysispoliecon/61d537bffd897800018a615c
Yiu, C.Y. (2021a) Trace the Impacts of Omicron on Colab, Medium, December 15. https://ecyy.medium.com/trace-the-impacts-of-omicron-on-colab-da2e96aa360c
Yiu, C.Y. (2021b) How to Calculate Annualised Rate of Return — a what-if goal seek approach using Excel, Medium, November 22. https://ecyy.medium.com/how-to-calculate-annualised-rate-of-return-a-what-if-goal-seek-approach-using-excel-1a11327204f5
