MERS-CoV outbreak: infectious disease genomics in action

Dr Leila LuheshiMonday, 28 April 2014

In September 2012, reports from Saudia Arabia described the appearance of a severe acute respiratory illness which was causing death in nearly 50% of cases. Laboratory investigations revealed that this infection was caused by a virus that had never before been seen in humans (see previous news).

Cases of infection with this virus, now called Middle East Respiratory Syndrome Coronavirus (MERS-CoV) have continued to occur, predominantly in the Arabian Peninsula, with the total number of confirmed cases in Saudia Arabia alone now in excess of 300 with over 100 deaths resulting. While there is evidence that MERS-CoV can pass from person to person, currently it is not believed to be capable of sustained transmission in humans. Instead, evidence suggests that MERS-CoV circulates mainly in animals, camels being the primary suspects, and that humans are acquiring the infection predominantly through contact with infected animals.

In recent weeks there has been a sharp rise in cases of MERS-CoV in some parts of Saudia Arabia, and this has led to concerns that the virus may have mutated to become more efficient at transmitting itself from person to person. This has led the health authorities in Saudia Arabia to team up with virologists at the University of Bonn in Germany to sequence the genomes of MERS-CoV virus isolated from patients.

In one of the first examples of real-time use of pathogen genome sequencing to study the epidemiology of an outbreak, the scientists in Bonn were able to compare the genomes of viruses from patients infected with MERS-COV in April 2014 with those infected earlier in the outbreak. They did not find any significant changes in the genome that might explain an increase in the ability of the virus to transmit from one person to another, and in particular they found that the gene most likely responsible for enabling the virus to infect a new ‘host’ was identical in these newer cases and many of the older ones.

Information about the genomes of viruses and bacteria causing outbreaks is crucial to informing the efforts of clinicians, epidemiologists and health authorities to control their spread. The knowledge that the increase in cases of MERS-COV doesn’t seem to be due to changes in their genome suggests instead that inadequate hygiene and infection control measures, or simply enhanced rates of detection through more careful surveillance, may explain this increase in cases. Armed with this information, health authorities can inform the public more accurately about risk of infection and concentrate their efforts on the actions required to control this potentially fatal disease.

The forthcoming introduction of pathogen genome sequencing in the UK and in other countries around the world has the potential to significantly improve our ability to monitor, understand and control outbreaks of infectious disease. The power of the genome sequence is that it provides the most detailed possible picture of the capabilities and ancestry of a virus or bacteria, and thus the most accurate understanding of its disease-causing behaviour.

The challenge for health policy makers around the world is to build systems to ensure that where there are infectious disease outbreaks of global significance such as MERS-COV, the genomic sequence data from patients’ infections are shared openly, rapidly and effectively. This action is vital to enabling the co-ordination of global infection control responses to existing threats and early detection of any new and emerging infectious disease threat.