Connect with us

Coronavirus Explainers

COVID-19 Pandemic Explained: What Is Reproduction (R) Number And Why Does It Matter?

According to experts, R number helps in understanding how fast and wide is the infection spreading; but what exactly is the R number and why does it matter during the ongoing COVID-19 pandemic?

COVID-19 Pandemic Explained: What Is Reproduction (R) Number And Why Does It Matter?
  • The latest R effective estimate for the country is 0.90
  • R value tells how many people are infected by one infected person
  • An R value of less than 1 suggests that the rate of infection is slow

New Delhi: In the past 11 months of the COVID-19 pandemic, we have gained a decent grasp on once-unpopular terms and concepts like personal protective equipment (PPE), social distancing, doubling rate and “flattening of the curve”. We have all seen ourselves grow from being completely clueless about the infectious disease to becoming budding armchair virologists. However, there is one phrase used widely but may still confuse many: the Reproduction or R number. According to experts, R number is an important parameter to know the spread of an infectious disease. The aim while fighting a pandemic should be to shrink the R number below 1 and keep it there, say experts. NDTV spoke with Dr Chandrakant Lahariya, epidemiologist, vaccinologist, and public health and policy expert based in Delhi and Dr Preeti Kumar, Vice President- Public Health System Support at the Public Health Foundation of India to know what is R number and why does it matter.

Also Read: Study Uncovers Subset Of COVID-19 Patients Who Recover Quickly And Sustain Antibodies

According to Dr Lahariya, R refers to an infectious disease’s capacity to spread. It signifies the average number of people that one infected person will pass the virus to. In other words, it measures the number of new cases from one infected person. Explaining further he said,

R number changes over the course of time due to various factors like how infectious the disease is, how it develops, how a population behaves, immunity among people from the infection or vaccine, and other such factors.

He further added that a place that is densely populated is likely to have a higher R than a sparsely populated area.

R0 And Rt

R number is represented by R0 or ‘R nought’ and Rt or ‘Effective Reproduction Number’ or simply ‘R Effective’.

According to Dr Kumar, R0 is the average number of secondary infections by a typical case, where everyone is susceptible or is not immune to the disease which happens at the beginning of an epidemic or a pandemic. For example, if R0 is 5, it indicates that each infected person will infect at least five other people and each of those five persons will infect five more persons and so on. She said that R0 is affected by the rate of contacts in the population, the probability of infection being transmitted, and the duration of infectiousness. She said,

An R0 value matters because above 1 means that the epidemic will grow exponentially, while below 1 means it is not growing and the disease will eventually stop spreading. We all want R0 below 1 which shows that not enough new people are being infected to sustain the outbreak.

R0 can be brought below 1 once the infected persons transmit the disease to less than 1 person, on an average. This can be achieved when people gain immunity against the infection either via vaccine or herd immunity which is a stage where enough people become immune by getting infected naturally and fighting it that more people are not catching the infection. As per experts, Measles is one of the diseases that have a high R0 of 15 in populations with immunity. This implies that on average, one person will spread measles to 15 others.

Also Read: COVID-19 Explained: How Can Winter Season Impact India’s Current Declining COVID Trend?

Rt, on the other hand, is a measure of 1 person infecting the number of other persons in a population among whom the precautionary measures to avoid the infection are being followed strictly. In the case of COVID-19, the precautionary measures include wearing masks in public, maintaining social distancing, washing hands regularly, wiping high-touch surfaces frequently among others. If the Rt is 3, this means that one infected person can pass on the infection to three more persons and those three will further infect three each on an average. But by following recommended safety measures Rt can be brought down to less than 1 which means that the transmission is slowing down.

According to Dr Lahariya, R is calculated using data such as the number of people dying, admitted to hospital or testing positive for the virus over time.

During the initial days of the pandemic, in March and April, the Rt value in the country was more than 2 which decreased to less than 1 in September. The latest R effective estimate for the country is 0.90. Regionally if we see, on Thursday, November 5, Himachal Pradesh recorded the highest Rt value in India at 1.20. Haryana recorded the second-highest Rt value at 1.19. This was followed by Delhi and Mizoram at 1.18, Ladakh at 1.08 and Chandigarh at 1.05. On the other hand, Karnataka recorded the lowest Rt value in the country at 0.54. This was followed by Puducherry at 0.62, Nagaland at 0.66, Assam at 0.73, Bihar at 0.77, and Arunachal Pradesh and Tripura at 0.83.

The experts warn against complacency that may set in among the public and the authorities as the R number goes below 1. This is because until the immunity is built against the virus, any negligence can result in an increase in R number.

Also Read: One Of The Puzzles Of COVID-19 Is The Large Proportion Of People Who Are Asymptomatic: Dr Vincent Rajkumar Of Blood Cancer Journal

NDTV – Dettol Banega Swasth India campaign is an extension of the five-year-old Banega Swachh India initiative helmed by Campaign Ambassador Amitabh Bachchan. It aims to spread awareness about critical health issues facing the country. In wake of the current COVID-19 pandemic, the need for WASH (WaterSanitation and Hygiene) is reaffirmed as handwashing is one of the ways to prevent Coronavirus infection and other diseases. The campaign highlights the importance of nutrition and healthcare for women and children to prevent maternal and child mortality, fight malnutrition, stunting, wasting, anaemia and disease prevention through vaccines. Importance of programmes like Public Distribution System (PDS), Mid-day Meal Scheme, POSHAN Abhiyan and the role of Aganwadis and ASHA workers are also covered. Only a Swachh or clean India where toilets are used and open defecation free (ODF) status achieved as part of the Swachh Bharat Abhiyan launched by Prime Minister Narendra Modi in 2014, can eradicate diseases like diahorrea and become a Swasth or healthy India. The campaign will continue to cover issues like air pollutionwaste managementplastic banmanual scavenging and sanitation workers and menstrual hygiene


Coronavirus has spread to 195 countries. The total confirmed cases worldwide are 23,96,06,768 and 48,82,051 have died; 20,13,42,617 are active cases and 3,33,82,100 have recovered as on October 15, 2021 at 4:15 am.


3,40,37,592 16,862Cases
3,33,82,100 19,391Recovered
4,51,814 379Deaths
In India, there are 3,40,37,592 confirmed cases including 4,51,814 deaths. The number of active cases is 2,03,678 and 3,33,82,100 have recovered as on October 15, 2021 at 2:30 am.

State Details

State Cases Active Recovered Deaths

65,86,280 2,384

33,157 6

64,13,418 2,343

1,39,705 35


48,29,944 9,246

96,421 1,802

47,06,856 10,952

26,667 96


29,82,399 310

9,607 43

29,34,870 347

37,922 6

Tamil Nadu

26,83,396 1,259

15,451 199

26,32,092 1,438

35,853 20

Andhra Pradesh

20,59,122 540

6,588 27

20,38,248 557

14,286 10

Uttar Pradesh

17,10,008 12

135 4

16,86,976 16


West Bengal

15,79,012 530

7,576 81

15,52,491 601

18,945 10


14,39,311 28

337 1

14,13,885 29



10,33,809 521

4,890 38

10,20,645 477

8,274 6


10,05,614 16

203 4

9,91,841 20



9,54,382 8

42 6

9,45,386 2



8,26,244 34

215 20

8,15,943 14


Madhya Pradesh

7,92,669 12

111 1

7,82,035 11



7,71,035 16

105 158


10,049 174


7,26,016 8

42 6

7,16,313 2



6,68,618 168

4,171 40

6,60,512 207

3,935 1


6,05,847 207

3,646 157

5,96,263 362

5,938 2


6,01,971 33

234 11

5,85,199 16

16,538 6


3,48,406 11

130 4

3,43,141 7



3,43,729 28

175 22

3,36,157 6


Jammu And Kashmir

3,30,834 93

935 11

3,25,473 104


Himachal Pradesh

2,21,113 182

1,387 5

2,16,011 173

3,715 4


1,77,356 68

679 27

1,73,342 39

3,335 2


1,27,259 49

647 4

1,24,763 53



1,22,432 69

1,444 15

1,19,099 84



1,10,719 901

13,601 435

96,744 1,332

374 4


84,295 4

110 8

83,369 12



82,734 87

892 31

80,411 115

1,431 3


65,295 10

32 5

64,443 15


Arunachal Pradesh

54,958 4

202 22

54,476 26



31,722 6

224 1

31,108 7



31,516 9

230 8

30,613 17



20,867 6

44 2

20,615 4


Dadra And Nagar Haveli


3 1

10,668 1




2 0



Andaman And Nicobar Islands

7,640 3

10 1

7,501 2


Coronavirus Outbreak: Full CoverageTesting CentresFAQs

Click to comment

Leave a Reply

Your email address will not be published. Required fields are marked *

Highlights From The 12-Hour Telethon

Leaving No One Behind

Mental Health


Join Us