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The SARS-CoV-2 virus responsible for causing Covid-19 disease is shed into the environment by both symptomatic and asymptomatic patients. Respiratory droplets and aerosols are the primary routes of viral shedding. Viral particles remain viable on plastic and stainless steel up to 72 hrs. Other studies have demonstrated an interaction between air particles and viruses, suggesting that an increase in environmental dust concentration by 10 µg/m3 was associated with a higher incidence of viral infection. The persistent nature of viral particles after shedding in the environment near infected individuals implicates potential viral contamination and transmission. Therefore, extensive environmental surveillance is needed especially in the areas housing infected patients to help identify the potential spread of the disease.
One such study is undertaken by researchers at the Ohio State University. They collected the dust samples from the rooms where Covid-19 patients were quarantined and from two houses where Covid-19 positive patients lived. Using techniques like quantitative reverse transcription PCR (RT-qPCR), chip-based digital PCR (dPCR), and droplet digital PCR (ddPCR), researchers found the viral RNA in 97% of the dust samples and 55% of the surface swabs. The team analyzed the samples on the day of collection and every subsequent week for a month. The presence of SARS-CoV-2 RNA (virus genetic material) was detected even after four weeks.
Because the Covid-19 isolation rooms were sprayed with a chlorine-based disinfectant prior to sample collection, the researchers believe that it likely destroyed the crown-like spike envelope around the virus, an essential structural component of the virus that plays a major role in the disease transmission. This could likely inactivate the virus and make it ineffectual for transmission.
Viral particles after shedding from infected humans integrated into the dust which could be used for environmental surveillance of viral disease outbreaks. This study offers a non-invasive way for monitoring indoor dust as an important tool for environmental monitoring of Covid-19 outbreak areas and high-risk buildings.
Viral RNA persistence in the environmental dust should be taken into consideration when determining the occurrence of a past or recent viral disease outbreak. We need more such research to validate the findings and to utilize this surveillance technique on a larger scale to mitigate viral transmission.
