Scientists from China and Singapore recently reported the discovery of an Ebola-like virus in the liver of fruit bats in Yunnan Province, China. The Mengla virus, named for the county it was discovered in, shares many of the characteristics of the deadly Ebola virus and has the potential to infect humans.

The Mengla virus belongs to the small but deadly family of filoviruses, which includes Ebolavirus, Marburgvirus and Cuevavirus. These viruses are known to cause severe haemorrhagic fever in humans, apes and monkeys, but there is no suggestion that the Mengla virus has been transmitted to humans.

Scientists in China had previously found evidence, in the form of antibodies, of several filoviruses in Rousettus and Eonycteris bats and provided evidence that they were filoviruses – initially labelled as “unclassified”. These same scientists then extended their investigation to explore the genetics of a virus collected from Rousettus bats from Mengla County.

Having genetically sequenced the Mengla virus, they discovered that it has 32-54% genetic similarity with known filoviruses and sits somewhere between the Ebola and Marburg viruses on the evolutionary tree. However, the Mengla virus is different enough to warrant its own genus. The new genus has been named Dianlovirus, and it sits in the filovirus group.

The genome of the Mengla virus indicated that it carries a protein on its surface that is similar to other filoviruses that can infect mammals. They found that the Mengla virus uses the same NPC1 receptor that other filoviruses use to enter and infect cells, which suggests that it could infect humans, monkeys, dogs, hamsters and bats. The virus has the potential to either infect humans directly or by first infecting other animals. However, further studies are needed to demonstrate this potential.

The scientists also compared this novel virus genome to Ebola and Marburg viruses and identified incredible similarity in how the genome is organised. Although scientists have not yet sequenced the entire genome of the virus, there is convincing evidence that the Mengla virus can jump to humans through urbanisation and deforestation and the close interaction between humans and animals that this encourages.

Bat-borne viruses

Among all wildlife species, bats represent the second most diverse group of mammals and harbour more than 65 human pathogens. Bats are particularly well known as carriers of filoviruses.

In 2018, a new Ebola virus was discovered in free-tailed bats in Sierra Leone. The characteristics of the newly named Bombali virus is similar to previously discovered Ebola viruses, but the risk to humans is higher because free-tailed bats are known to roost in people’s homes. And at least one species of bat in Africa has been found to host the Marburg virus, indicating the potential role of bats in the spread of filoviruses due to close residential dwelling between human and bats.

Recent discoveries of novel viruses in bats and their potential in spreading diseases has threatened global public health, especially in Africa due to the consumption of bat “bushmeat”. Moreover, hunting bats for both food and money has put humans at significantly higher risk of zoonotic (from animal to human) spillover of viruses.

The recent filovirus outbreaks have challenged health officials in Africa in containing the disease to borders and hindering the spread to Europe. Now identification of this new Mengla virus explains the genetic diversity of filoviruses beyond Africa. It is a warning that we need to continuously monitor and swiftly respond to emergency situations of possible future disease emergence.

Different novel viruses have been reported in bats in the last decade, which underlines the need to continuously study the diversity of emerging viruses and their potential to cause infection in human and other animals. These insights will help to plan future mitigation strategies, including control and treatments as well as long-term management of disease risks.