How does COVID-19 actually infect humans? World's first human challenge study reveals
A tiny virus-laden droplet can infect someone with COVID-19 (representative image).
Coronavirus has been tormenting the whole world for last two years. The number of cases is still rising in some countries. Ever wondered how does it actually infects humans? Well, now we have an answer to this riddle.
A tiny virus-laden droplet can infect someone with COVID-19, said a study.
The findings of the research, where volunteers were deliberately infected with the SARS-CoV-2 virus, has been published in the journal ‘Nature Medicine’ on Thursday. This is the world's first human challenge study.
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Challenge studies involve intentionally giving someone a virus to study its effects on the human body. It is risky but hugely valuable to understand the course of an infection.
"Really, there's no other type of study where you can do that, because normally, patients only come to your attention if they have developed symptoms, and so you miss all of those preceding days when the infection is brewing," said Dr Christopher Chiu, an infectious disease physician and immunologist at Imperial College London and the lead author of the study.
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The study, which began in March 2021, had volunteers aged between 18 and 30. The volunteers were infected with the originally detected strain of the virus.
They were monitored medically for 24 hours a day. They also stayed at London's Royal Free Hospital for two weeks.
A total of 18 participants became infected. Two never developed symptoms. Around 83% study participants, who got infected, lost sense of smell.
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The illnesses were mild. Some had congestion, stuffy noses, sneezing and sore throats.
It found that about 10 microns, which is the amount in a single droplet someone sneezes or coughs, can make someone sick.
Covid has a short incubation period. After infection, it takes two days for a person to start shedding virus. People shed high amounts of virus before showing symptoms.
Around hours after virus was introduced, it could be detected in the back of the throat. It takes 58 hours for virus to show up on swabs from the nose.
(With inputs from agencies)