How coughing and sneezing could re-aerosolise Covid virus and push it deeper into your lungs

‘We could look at interventions that would either delay or reduce the possibility of lower respiratory tract infection. Strategies such as administering cough suppressants or expectorants can prevent this re-aerosolisation and deep lung infection,’ say researchers from IIT-Madras, Jadavpur University and Northwestern University, US

The viral colonies in the mucosal layer get dislodged due to violent events like coughing and sneezing. (Source: Freepik)

Listen to this article

00:00

1x 1.5x 1.8x

Coughing and sneezing can dislodge colonies of respiratory viruses such as Sars-CoV-2 from the throat and re-aerosolise them, which when inhaled, go deeper into the respiratory system. Such repeated aerosolisation of the virus is how it reaches the lungs and infects them, according to a recently published paper by researchers from IIT-Madras, Jadavpur University and Northwestern University from the US.

Although we know that the virus that causes Covid-19 can cause upper respiratory tract symptoms like sore throat as well as lower respiratory tract symptoms like pneumonia, how the infection reaches from the mouth and nose to the lungs is not known.

The researchers used mathematical models of viral replication within the body and various modes of transmission to arrive at the conclusion. “The idea was to come up with a plausible mechanism for how the virus travels from the nasopharynx to the lower respiratory tract. This is important because we know that it is only when the infection reaches the lungs that we get severe disease with pneumonia and cytokine storm,” said Prof Mahesh Panchagnula from the Department of Applied Mechanics at IIT-Madras. He emphasised that this is just a probable mechanism as there is no way to study this happening within a patient.

There were several theories such as the virus travelling through the mucous membrane to the lungs, the virus getting into the bloodstream and entering the lungs, or the virus being inhaled deeply into the lungs. But the timeline from the symptoms appearing to a person getting pneumonia did not match with these theories.

Dr Panchagnula said, “Our theory is that the viral colonies in the mucosal layer get dislodged due to violent events like coughing and sneezing. They then become re-aerosolised and are inhaled by the person, transmitting the infection deeper in the respiratory tract. This process continues till eventually the virus reaches the lower respiratory tract. This process, our mathematical model showed, takes about four to five days which is clinically what we have seen in Covid-19 patients.”

The researchers used the model with influenza virus as well to arrive at the same conclusion.

He added, “We believe that once we understand these mechanisms, we could look at interventions that would either delay or reduce the possibility of lower respiratory tract infection. Strategies such as administering cough suppressants or expectorants can prevent this re-aerosolisation and deep lung infection.

Story continues below this ad

Elaborating further, Dr Aranyak Chakravarty, Assistant Professor, School of Nuclear Studies and Application, Jadavpur University, said, “There was another important finding of this work. Our studies also show that while the transport of infected mucous droplets in the airway plays an important role, the infection growth and seriousness also depend upon the immune response of the infected person.”

ALSO READ | Union Budget 2023: Health budget is now Covid negative

The researchers have shown that an activated immune system – either because of previous infection or vaccination – can lead to higher presence of antibodies initially, neutralising a high number of viruses and slowing replication. This reduces the number of viral particles that are able to go into the lungs, thereby reducing the severity and time it takes to heal the infection.

ALSO READ | Past COVID-19 infection can protect against reinfection, as good as 2 vaccine doses: The Lancet

Prof Neelesh Patankar from the Department of Mechanical Engineering at Northwestern University said, “This finding reinforces the importance of vaccination in preventing severe infection. Vaccines help the body make special cells called B-lymphocytes and T-lymphocytes (or memory cells). T− lymphocytes suppress virus multiplication. B lymphocytes generate antibodies that destroy the virus.”

Anonna Dutt

Anonna Dutt is a Principal Correspondent who writes primarily on health at the Indian Express. She reports on myriad topics ranging from the growing burden of non-communicable diseases such as diabetes and hypertension to the problems with pervasive infectious conditions. She reported on the government’s management of the Covid-19 pandemic and closely followed the vaccination programme. Her stories have resulted in the city government investing in high-end tests for the poor and acknowledging errors in their official reports. Dutt also takes a keen interest in the country’s space programme and has written on key missions like Chandrayaan 2 and 3, Aditya L1, and Gaganyaan. She was among the first batch of eleven media fellows with RBM Partnership to End Malaria. She was also selected to participate in the short-term programme on early childhood reporting at Columbia University’s Dart Centre. Dutt has a Bachelor’s Degree from the Symbiosis Institute of Media and Communication, Pune and a PG Diploma from the Asian College of Journalism, Chennai. She started her reporting career with the Hindustan Times. When not at work, she tries to appease the Duolingo owl with her French skills and sometimes takes to the dance floor. ... Read More