Faeces samples can harbour infectious coronavirus, study finds

img-20200423-wa00145530353614599350907.jpg

Chinese researchers were able to isolate and culture novel coronavirus from faeces samples. Confirmation of infectious virus in faeces samples raises the potential for faecal-oral or faecal-respiratory transmission. During 2002 SARS, 329 residents of a private housing estate in Hong Kong were infected and 42 died due to aerosolised faeces spread of the virus.

Researchers in China have isolated infectious novel coronavirus from faeces samples of a patient who died. While other researchers were able to show viral RNA in urine and faeces samples using molecular tests, such studies have not been able to tell if the virus was infectious in nature. The latest study by a team led by Jincun Zhao from Guangzhou Institute of Respiratory Health, Guangzhou in China was able to confirm infectiousness of the virus isolated from faeces samples.

Confirmation of infectious virus in faeces samples raises the potential for faecal-oral or faecal-respiratory transmission through aerosolised faeces. The results were published in the journal Emerging Infectious Diseases.

During the 2003 SARS pandemic, 329 residents of a private housing estate in Hong Kong were infected and 42 died. Investigation of the building’s structure showed that faulty sewage pipelines led to aerosolisation of contaminated faeces, which was believed to be the source of infection.

Significance of findings

“Our findings indicate the need for appropriate precautions to avoid potential transmission of SARS-CoV-2 from faeces. Discharge and hospital cleaning practices should consider this possibility for critically ill patients or those who died who had high viral loads and are more likely to shed infectious virus,” they write.

Earlier, another team of researchers from China were able to isolate the virus from a single stool specimen and culture the virus. This led to the World Health Organization recognising that “coronavirus infection may lead to intestinal infection and be present in faeces”. According to the WHO, there are “no reports of faecal-oral transmission of the COVID-19 virus” so far.

Routes of transmission

The main routes of transmission for SARS-CoV-2 virus so far known include droplet transmission and contact with contaminated surfaces. On March 29, the WHO recognised airborne transmission of novel coronavirus. In airborne transmission, the virus is present within droplet nuclei, which are generally considered to be particles less than 5 micron in diameter, can remain in the air for long periods of time and be transmitted to others over distances greater than one metre.

Isolation of virus

On January 17, 2020, a 78-year-old man who had a history of recent travel to Wuhan, China, was admitted to a hospital. The first faeces specimen was collected on January 27 and tested positive for viral RNA. Researchers also collected samples on three more days, and all samples were positive for viral RNA.

They were able to isolate, culture the virus and even sequence the whole genome of the virus. The viral load was higher in faeces than in respiratory specimens collected at multiple time points (17–28 days after symptom onset), they write. They were however not able to isolate the virus from faeces samples collected at later time points suggesting that the virus in faeces was not infectious when collected at later time points of disease onset.

In all, the researchers collected faeces specimens from 28 patients and were able to isolate the virus from two of the three patients. This indicates that infectious virus in faeces is a “common manifestation” of COVID-19, they say.

Published in The Hindu on May 23, 2020