Explainer: What does the data tell us about coronavirus being spread through human waste?

On January 20, Chinese officials confirmed human-to-human transmission of the novel coronavirus after more than 200 confirmed cases were announced. At the time of writing this article, there are more than 450,000 cases of Covid-19 with more than 20,000 deaths worldwide.

People know that the virus spreads through droplets – which is why it is important to wash your hands and for those who are sick to wear masks. But are there other ways that Covid-19 spreads?

“A study in the @TheLancet shows that coronavirus lingers on human excreta much longer than in respiratory samples,” actor Amitabh Bachchan said in a video he posted on Twitter. His tweet was retweeted by Prime Minister Narendra Modi and the official account of Swachh Bharat, the government sanitation scheme.

Why should we consider the possibility of faecal-oral transmission?

Faecal-oral transmission occurs when contaminated faeces of one person is somehow ingested by another. This usually happens when people don’t or aren’t able to wash their hands after visiting the toilet. Anything this person touches afterwards could get contaminated, and the germs may eventually be ingested by someone else.

The Severe Acute Respiratory Syndrome Coronavirus 2, or SARS-CoV 2, which causes the current Covid-19 pandemic, belongs to a family of Human coronaviruses.

The other Human coronaviruses, such as SARS-CoV which caused the SARS epidemic in 2003 and Middle East Respiratory Syndrome coronavirus which was responsible for MERS outbreaks from 2012, are known to cause respiratory and digestive symptoms (like diarrhoea, abdominal pain and vomiting).

“The genome sequence of SARS-CoV-2 is 82% similar to SARS-CoV,” according to a study in the Lancet.

Between 16-73% of patients with SARS had diarrhoea and SARS-CoV RNA was detected in stools. The viral RNA was present in the faeces of some patients even after 30 days of illness. About 25% of patients with MERS-CoV reported digestive symptoms such as diarrhoea or abdominal pain. Some patients initially had only fever and abdominal symptoms without respiratory symptoms. MERS-CoV RNA was found in 15% of stool samples from patients with MERS-CoV.

In early reports from Wuhan, the city in China where the Covid-19 outbreak began, 2%-10% of patients with Covid-19 had gastrointestinal symptoms. Abdominal pain was reported more common in patients admitted to the intensive care unit and one in 10 patients presented with diarrhoea and nausea one or two days before the developing of fever and respiratory symptoms.

This is important because most people think of Covid-19 as a severe form of flu or cold and don’t know that they could develop abdominal pain or vomiting before typical flu symptoms.

Was there faecal-oral transmission during outbreaks of SARS & MERS?

There are some suggestive data.

SARS-CoV RNA was found in the sewage water of two hospitals in Beijing treating patients with SARS. In an experiment with viral seeding of sewage water, the virus was found to remain infectious for 14 days at 4°C, but for only two days at 20°C. The virus started dying after 24 hours at 38°C and 80%-90% relative humidity.

MERS-CoV is viable in low temperature, low humidity conditions. The data suggests the potential for coronaviruses to be transmitted through contact with traces of faecal matter on surfaces in conditions with low temperatures and humidity.

The novel coronavirus that causes Covid-19 has been found in Dutch sewage.

Does detection of genetic material in stool mean transmission?

SARS-CoV-2 RNA has also been detected in the stool of the first patient in the USA.

The detection of viral RNA in other samples like saliva and stool, however, doesn’t necessarily mean transmission unless the virus can be cultured – isolated and grown in the lab – from the RNA.

Two independent laboratories from China declared that they have successfully isolated live SARS-CoV-2 from the stool of patients. It suggests shedding – which is the passing on – of live virus.

A further positive viral culture from saliva suggests the possibility of salivary gland infection and possible transmission.

What does the data suggest regarding virus in faeces of Covid-19 patients?

A study of 73 Covid-19 patients showed that once the virus infects the digestive tract inner layer, more than 50% of patients shed virus in faeces and can transmit it, and around 20% patients continue to shed virus even after negative conversion of viral RNA in respiratory tract.

A large study of 205 patients showed that 30% of patients had positive RNA in stool samples. Live SARS-CoV-2 was observed in the stool sample from two patients who did not even have diarrhea.

A case of Covid-19 was reported in China with persistent negative tests from respiratory samples but a positive stool test.

Recent data suggests the possibility of extended duration of viral shedding in faeces, for nearly 5 weeks after the patients’ respiratory samples tested negative for SARS-CoV-2 RNA.

Why is faecal oral transmission important?

It may help explain the rapid spread of disease.

No cases of transmission via the faecal-oral route have yet been reported for SARS-CoV-2, which might suggest that infection via this route is unlikely in quarantine facilities, in hospital, or while under self isolation.

Potential faecal-oral transmission, however, might pose an increased risk in contained living premises such as hostels, dormitories and cruise ships.

This is particularly important in countries like India which have poor sanitation, though the previous data suggests that coronaviruses require low temperatures and low humidity for prolonged survival.

Should the current Covid-19 guidelines be changed with the new data available?

The American Food and Drug Authority has issued a safety alert for fecal microbiota transplantation procedures due to potential for transmission of the Covid-19 virus through FMT (a procedure that delivers human donor stool into the colon of a patient to treat certain infections).

Current American Centres for Disease Control and the Indian Ministry of Health and Family Welfare guidance for discharge of patients with Covid-19 is based on negative results of PCR testing for SARS-CoV-2 from at least two sequential upper respiratory tract specimens like throat swab collected ≥24 hours apart.

Respiratory transmission is still the primary route for SARS-CoV-2 and evidence is not yet sufficient to develop practical measures for the group of patients with negative respiratory tract sample results but positive faecal samples. Further research into the viability and infectivity of SARS-CoV-2 in faeces is required.

However, faeces testing should be performed routinely in Covid-19 patients, and transmission-basedprecautions for hospitalised Covid-19 patients should continue, if faeces tests positive.

India appears to not have done any faeces testing of Covid-19 patients yet – something the authorities must consider.

What precautions should one take?

Coronaviruses are susceptible to antiseptics containing ethanol, and disinfectants containing chlorine or bleach.

Strict precautions must be observed when handling the stools of patients infected with coronavirus, and sewage from hospitals should also be properly disinfected. Sewage workers should be provided protective outer clothing, gloves, boots, safety glasses, mask and face protection.

The importance of frequent and proper hand hygiene should be emphasised, as well as the need to eat cooked food and to clean and air dry utensils after washing.

Here is a full list of guidelines to follow to ensure that you prevent this mode of virus transmission as well.

Dr Amith Viswanath’s Twitter handle is @avstmd.