A new research suggests that dromedary camels could be responsible for passing to humans the deadly MERS coronavirus that emerged last year.
Tests have shown the MERS (Middle East Respiratory Syndrome) virus, or one that is very closely related, has been circulating in the animals, offering a potential route for the spread.
The study is published in the journal Lancet Infectious Diseases.
But the scientists say more research is needed to confirm the findings.
The MERS coronavirus first emerged in the Middle East last year. So far, there have been 94 confirmed cases and 46 deaths.
While there has been evidence of the virus spreading between humans, most cases are thought to have been caused by contact with an animal. But until now, scientists have struggled to work out which one.
To investigate, an international team looked at blood samples taken from livestock animals, including camels, sheep, goats and cows, from a number of different countries.
Dromedary camels could be responsible for passing to humans the deadly MERS coronavirus
They tested them for antibodies – the proteins produced to fight infections – which can remain in the blood long after a virus has gone.
Professor Marion Koopmans, from the National Institute of Public Health and the Environment and Erasmus University in The Netherlands, said: “We did find antibodies that we think are specific for the MERS coronavirus or a virus that looks very similar to the MERS coronavirus in dromedary camels.”
The team found low levels of antibodies in 15 out of 105 camels from the Canary Islands and high levels in each of the 50 camels tested in Oman, suggesting the virus was circulating more recently.
“Antibodies point to exposure at some time in the life of those animals,” Prof. Marion Koopmans explained.
No human cases of the MERS virus have been reported in Oman or the Canary Islands, and the researchers say they now need to test more widely to see if the infection is present elsewhere.
This would include taking samples from camels in Saudi Arabia, the country where the virus is the most prevalent.
Prof. Marion Koopmans said: “It is a smoking gun, but it is not definitive proof.”
Health officials say confirming where the virus comes from is important, but then understanding how humans get infected is a priority.
Gregory Hartl, from the World Health Organization, said: “Only if we know what actions and interactions by humans lead to infection, can we work to prevent these infections.”
Data suggests that it is not yet infectious enough to pose a global threat and is still at a stage where its spread could be halted.
The new Middle East Respiratory Syndrome (MERS) virus, which has killed half of those infected, is “unlikely” to reach the same scale as SARS, ministers in Saudi Arabia say.
Most of the 90 MERS cases reported so far have been in Saudi Arabia.
MERS is from the same group of viruses as the common cold and SARS, which killed 774 people.
However, a detailed analysis of the Saudi cases, published in Lancet Infectious Diseases, did warn of “major gaps” in understanding of the virus.
The MERS coronavirus emerged in 2012 and has infected 90 people worldwide, 45 of them have died.
MERS is from the same group of viruses as the common cold and SARS, which killed 774 people
The global concern is that cases could spread much further, echoing the SARS outbreak.
Cases have been centered on the Middle East – with patients in Jordan, Qatar, Saudi Arabia and the United Arab Emirates. Additional cases in France, Germany, Italy, Tunisia and the UK have all been linked to travel to the Middle East.
Researchers in Saudi Arabia have published details of the 47 cases reported in the country.
They suggest a pattern of mostly older men being infected. Most cases were also in people with other medical problems, more than two-thirds of the reported cases also had diabetes.
The lead researcher and Deputy Minister for Public Health, Prof. Ziad Memish, said: “Despite sharing some clinical similarities with SARS, there are also some important differences.
“In contrast to SARS, which was much more infectious especially in healthcare settings and affected the healthier and the younger age group, MERS appears to be more deadly, with 60% of patients with co-existing chronic illnesses dying, compared with the 1% toll of SARS.
“Although this high mortality rate with MERS is probably spurious due to the fact that we are only picking up severe cases and missing a significant number of milder or asymptomatic cases.
“So far there is little to indicate that MERS will follow a similar path to SARS.”
However, the latest Saudi investigation both highlighted the need to find where the virus was coming from.
Prof. Ziad Memish’s report said: “Reducing the rate of introduction of MERS coronavirus into human beings is unpredictable because the source of the virus is not yet known.
“We are searching vigorously for the source.”
New estimates suggest that one in six cancers, two million a year globally, are caused by largely treatable or preventable infections.
The Lancet Infectious Diseases review, which looked at incidence rates for 27 cancers in 184 countries, found four main infections are responsible.
These four – human papillomaviruses, Helicobacter pylori and hepatitis B and C viruses – account for 1.9 million cases of cervical, gut and liver cancers.
Most cases are in the developing world.
HPV infection can cause cervical cancer
The team from the International Agency for Research on Cancer in France says more efforts are needed to tackle these avoidable cases and recognize cancer as a communicable disease.
The proportion of cancers related to infection is about three times higher in parts of the developing world, such as East Asia, than in developed countries like the UK – 22.9% versus 7.4%, respectively.
Nearly a third of cases occur in people younger than 50 years.
Among women, cancer of the cervix accounted for about half of the infection-related cancers. In men, more than 80% were liver and gastric cancers.
Dr. Catherine de Martel and Dr. Martyn Plummer, who led the research, said: “Infections with certain viruses, bacteria, and parasites are some of the biggest and preventable causes of cancer worldwide
“Application of existing public-health methods for infection prevention, such as vaccination, safer injection practice, or antimicrobial treatments, could have a substantial effect on the future burden of cancer worldwide.”
Vaccines are available to protect against human papillomavirus (HPV) – which is linked to cancer of the cervix – and hepatitis B virus – an established cause of liver cancer.
And experts know that stomach cancer can be avoided by clearing the bacterial infection H. pylori from the gut using a course of antibiotics.
Commenting on the work, Dr. Goodarz Danaei from Harvard School of Public Medicine in Boston, the US, said: “Since effective and relatively low-cost vaccines for HPV and HBV are available, increasing coverage should be a priority for health systems in high-burden countries.”