The doubling rate of COVID-19 cases went up to 7.5 days in India: What does doubling rate mean and how is this an improvement?

Simply put, the doubling rate of an infectious disease or epidemic is referred to as the time taken for the total number of cases to double.

Myupchar April 21, 2020 17:35:31 IST
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The doubling rate of COVID-19 cases went up to 7.5 days in India: What does doubling rate mean and how is this an improvement?

On April 20, Lav Aggarwal, Joint Secretary, Health Ministry of India announced in a press briefing that due to the lockdown, the doubling rate of COVID-19 cases in India has gone up to 7.5 - the rate was 3.4 before the lockdown. 

He further said that if you look at the state-wise data, the rate is even better. Data till April 19 shows a doubling rate of 8.5 in Delhi, 9.2 in Karnataka, 9.4 in Telangana, 10.6 in Andhra Pradesh, 11.5 in Jammu and Kashmir and 13.1 in Punjab. 

The doubling rate of COVID19 cases went up to 75 days in India What does doubling rate mean and how is this an improvement

Representational image. Image by Tumisu from Pixabay.

The rate is even higher but below 20 in Tamil Nadu, Bugar and Chattisgarh, between 20 and 30 in Haryana, Ladakh, Himachal Pradesh, Chandigarh, Assam, Uttarakhand and Andaman and Nicobar. A doubling rate of more than 30 days is seen in Kerela and Odisha.

Three districts have had no new cases in the last 28 days and about 59 districts have had no cases for the last 14 days. In Goa, all the 7 COVID-19 patients have been cured already, bringing the total number of cases in the state to zero. 

Here is what doubling rate means and how this is a good sign for India.

Doubling rate

Simply put, the doubling rate of an infectious disease or epidemic is referred to as the time taken for the total number of cases to double. 

The rate depends on the R0 and the serial interval of a disease. R0, also called reproduction number, is a measure of the contagiousness of a disease and tells the numbers of people a single patient could infect in the time they are contagious. So, the R0 gives an idea of what would happen if an infected person would be present in a population of susceptible people. The R0 of COVID-19 is said to be somewhere between 1.5 to 3.5. Though this would vary depending on the prevention measures taken in an area and other factors like the susceptibility of the population.

The serial interval of the disease refers to the total time between the symptom onset on the primary patient (who first got the disease) and secondary patient (who got the disease from the primary patient). COVID-19 has an incubation period of about 1-14 days with an average of 5 days. The serial interval for COVID-19 is between 5-6 days as per the WHO. 

The incubation time of a disease is the time between the exposure of the pathogen to the appearance of first symptoms.  

If the R0 increases, the doubling time decreases - more cases show up quickly. And if the serial number increases, the doubling time increases - it would take time for new cases to show up.

So, the doubling time can be an important determining factor for how long and how quickly the quarantines and lockdowns need to be implemented to prevent the spread of the disease. 

Has India flattened the curve?

COVID-19 is a respiratory disease and spreads through coming in direct contact with an infected person or contaminated objects and through not maintaining respiratory hygiene -that is not covering your mouth while coughing or sneezing. Lockdowns were enforced in various parts of the world to contain the spread of the disease and people were asked to practice physical distancing (keeping a distance of at least 1 meter from everyone). 

In any epidemic, the initial exponential growth of cases is said to be the deciding factor for the severity of the epidemic. Experts say that all organisms including infectious microbes have a tendency to divide quickly and exponentially when they have unlimited resources - in this case susceptible people. In an exponential growth curve, the number of cases double over a given period of time in the pattern of 2,4,8,16 and so on. 

If left unchecked an exponential curve will peak itself and will slowly decline as the number of susceptible hosts reduces. However, data from the worst-hit countries have taught the world that with COVID-19 , this peak comes with the saturation of health resources and a lot of deaths.

On the other hand, countries with a comparatively flatter curve have taken to robust testing and isolation of confirmed cases to increase the doubling rate and control the spread of disease. As a result, their healthcare facilities were better able to deal with severe cases.

While many have commended the lockdown efforts, only time will tell how it affected the spread of the virus. And as far as flattening the curve is concerned, an increasing doubling rate is definitely a step in the right direction. 

For more information, read our article on When is an area considered a COVID-19 hotspot.

Health articles in Firstpost are written by myUpchar.com, India’s first and biggest resource for verified medical information. At myUpchar, researchers and journalists work with doctors to bring you information on all things health.

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