Doctors scrambling to figure out how the COVID-19 coronavirus has managed to infect so many people so quickly have found two ways in which the virus spreads - and they're desperately hoping to rule out a third.
Scientists in China have discovered the virus can be spread via faeces - like norovirus - which could explain how many people got infected, despite not being in direct contact with people carrying the disease.
Analysis of faeces samples from infected patients has found the virus alive and kicking, even after being excreted.
"This means that stool samples may contaminate hands, food, water, etc, and may cause infection by invading the oral cavity, respiratory mucosa, conjunctiva, etc," scientists at the Laboratory of the National Institute for Viral Disease Control and Prevention wrote in a paper this week.
"This virus has many routes of transmission, which can partially explain its strong transmission and fast transmission speed."
They said it emphasises the need for people in affected regions to keep washing their hands and disinfecting surfaces they come into contact with.
Another study out of China this week, this one published in journal Emerging Microbes & Infections, found COVID-19 - also known as 2019-nCoV - present in blood, oral and anal swabs, even after "days" of treatment.
"We cannot discharge a patient purely based on oral swabs negative, who may still shed the virus by oral–fecal route," the scientists said.
Droplets
But the primary route of transmission still appears to be respiratory - getting coughed or sneezed on, or touching something that has been - such as an infected person's hand - and then touching your own nose, mouth or eyes.
"Respiratory droplets and contact transmission are considered to be the most important routes of transmission of 2019-nCoV, but do not fully account for the occurrence of all [cases], and the reasons for the rapid spread of this virus."
COVID-19 is also able to transmit from person-to-person in this way before any symptoms show. A study published Thursday in the New England Journal of Medicine found some people without any symptoms have "viral loads... similar to that in the symptomatic patients".
Airborne
A third possible method of transmission - airborne - is yet to be confirmed. That's when the virus can hang around in the air after being expelled in a cough or sneeze - like measles.
Doctors at the US Centers for Disease Control and Prevention aren't taking any risks, recommending hospitals put suspected patients into airborne isolation rooms.
"That's the precaution we use for TB, measles, and chickenpox," Vito Iacoviello, infectious diseases expert at Mount Auburn Hospital in Cambridge, Massachusetts told Vox.
Airborne diseases are notoriously infectious. On average, each person who contracts measles spreads it to between 12 and 18 others, scientists estimate. So far, COVID-19's infection rate appears to be between two and three.
The COVID-19 death toll has now reached 2239, almost all of those within China.
