"This novel recombinant virus lineage appeared in Saudi Arabian camels as early as in July 2014, while human infections with viruses of this lineage were only reported from February 2015 onwards," Zhu said.

"The human MERS coronavirus identified in South Korea early this summer shows extremely high similarity to a camel virus sampled in March 2015 in Riyadh, indicating the origin of Korean viruses is from camels of the Middle East," he added.

The researchers also found two other coronaviruses co-circulating with the MERS coronavirus in the camels, including one closely related to the human 229E coronavirus that causes common colds in humans.

The results showed that around 6.9 percent of Saudi Arabian camels were simultaneously infected by two or three coronavirus species, and over half of the MERS coronavirus-positive camels were also infected with at least one other coronavirus.

Co-infections of different coronavirus species occur frequently in camels, highlighting the role of dromedary camels as an important host for coronaviruses, they said.

In addition, young dromedary camels, under one year old, played an important role in maintaining and spreading this virus.

In the second study, European researchers found after administering a candidate vaccine both nasally and intramuscularly, all camels developed detectable levels of antibodies against the MERS virus within three weeks.

Upon infection with the virus, these vaccinated camels experienced only mild clinical symptoms and were found to have significantly lower levels of the virus compared to those who did not receive the vaccine.

"This is nonetheless a very significant step forward in the fight against this pathogen," study author Joaquim Segales, lecturer at the Universitat Autonoma de Barcelona, said in a statement.

"Now we need to delve more deeply into the duration of the immunity and dosage before applying it in real situations."