Coronavirus: Outcome of unmitigated spread of COVID-19 decoded

70 % of the population was infected with COVID-19 within 7 months in the Brazilian city - Manaus.

By: Satata Karmakar | Edited by: Satata Karmakar | | Published: December 9, 2020 5:00 pm

Scientists decode outcome of unmitigated spread of COVID-19

In early 2020, COVID-19 virus began generating headlines all over the world because of the unprecedented speed of its transmission. Its origins have been traced to a food market in Wuhan, China, in December 2019. From there, it’s reached countries as distant as the United States and the Philippines. Also Read - COVID-19 Live Updates: Cases in India surge to 10,571,773 while death toll reaches 1,52,419

The virus (officially named SARS-CoV-2) has been responsible for millions of infections globally, causing hundreds of thousands of deaths. The United States is the country most affected. The disease caused by an infection with SARS-CoV-2 is called COVID-19. Also Read - Adverse events post Covid-19 vaccination: AIIMS' security guard admitted to ICU

While the whole world is right now struggling to find a way to stop the virus from spreading, a recent study has revealed what may happen if the virus doesn’t stop spreading. Also Read - Delhi health workers suffer mild reaction post COVID-19 vaccine: What you should expect

COVID-19 VIRUS TRANSMISSION AND BRAZIL

Scientists have analysed the spread of COVID-19 among people in Manaus, Brazil, where more than 70 per cent of the population was infected within seven months of the novel coronavirus arriving in the city, findings which shed light on what may happen if the disease spreads unmitigated.

Brazil has experienced one of the world’s most rapidly growing COVID-19 epidemics, with the Amazon being the worst-hit region, according to the researchers, including those from Harvard University in the US.

They said in Manaus, the largest metropolis in the Amazon, the first SARS-CoV-2 case was reported in mid-March, after which non-pharmaceutical interventions (NPIs), such as social distancing, were introduced.

THE UPS AND DOWNS OF THE VIRUS TRANSMISSION

This was followed by an “explosive” epidemic associated with relatively high mortality, and then by a sustained drop in new cases despite relaxation of NPIs, the study, published in the journal Science, noted.

To explore whether the epidemic was contained because infection reached the herd immunity threshold, or because of other factors such as behavioral changes and NPIs, the scientists collected data from blood donors in Manaus.

They inferred the virus attack rate from the collected blood samples and compared this data with that of Sao Paulo, which was less impacted.

The researchers estimated a 76 per cent attack rate in Manus by October, including adjustments for waning antibody immunity.

THE DETAILS ABOUT THE COVID-19 VIRUS ATTACK RATES

By comparison, the attack rate in Sao Paulo by October was 29 per cent, partly explained by the larger population size, they added.

Despite the tremendous toll the virus took in these two cities, the scientists said the attack rates remain lower than predicted in a mixed population with no mitigation strategies.

“It is likely that NPIs worked in tandem with growing population immunity to contain the epidemic,” they noted, also acknowledging voluntary behavioral changes as helping.

However, the scientists believe further studies in the region are “urgently” needed to determine the longevity of population immunity.

“Monitoring of new cases…will also be vital to understand the extent to which population immunity might prevent future transmission, and the potential need for booster vaccinations to bolster protective immunity,” they wrote in the study.

HOW DOES THE COVID-19 VIRUS SPREAD?

Data has shown that the virus that causes coronavirus disease 2019 (COVID-19) mainly spreads from person to person among those in close contact (within about 6 feet, or 2 meters). The virus spreads by respiratory droplets released when someone infected with the virus coughs, sneezes, or talks. These droplets can be inhaled or land in the mouth or nose of a person nearby.

Sometimes the COVID-19 virus can spread when a person is exposed to small droplets that stay in the air for several minutes or hours — called airborne transmission. It’s not yet known how common it is for the virus to spread this way.

It can also spread if a person touches a surface with the virus on it and then touches his or her mouth, nose, or eyes, but this isn’t the main way it spreads.

WHAT ARE THE WARNING SYMPTOMS

COVID-19 symptoms can be very mild to severe. Some people have no symptoms. The most common symptoms are fever, cough, and tiredness.

Other symptoms may include shortness of breath, muscle aches, chills, sore throat, headache, chest pain, and loss of taste or smell. This list is not all-inclusive. Other less common symptoms have also been reported. Symptoms may appear two to 14 days after exposure.

(With inputs from the Agencies)

Published : December 9, 2020 5:00 pm

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