Recent reports from Dr. Christian Drosten confirm that this past month’s surge in MERS cases can’t be explained by mutations to the virus.
…So what’s going on?
For the time being, my money’s on some sort of seasonality combined with increased surveillance.
Last year, we saw a similar – but much smaller – peak in incidence from April to June, followed by another in September – with lulls in between (markedly so in the winter months) [Figure 1]. If seasonality really is at play, one of the reasons we might be seeing more cases THIS April may be due to increased surveillance. More cases have been diagnosed this past month than ever before [Figure 1]… But perhaps more importantly, nearly two-thirds of all asymptomatic cases (43 of 69 total) reported in the history of MERS have been identified during this time period [Figure 2]. This suggests that the virus may indeed be more prevalent than we know… And that the current surge in cases may partly be due to increased screening of vulnerable populations – such as healthcare workers and those who have immediate contact with diagnosed cases – even if they don’t show symptoms.
Nevertheless, I must make clear that this theory is only speculation. To test it out, we need a clearer understanding of how humans acquire the virus from animal reservoirs (camels are currently our primary suspect) – as well as how the disease manifests in and transmits among humans. For the time being, all we can do is exercise patience. (Such is science!)
Note: Temporal data indicates date of onset, hospitalization, diagnosis, or public reporting.
Data Sources: KSA MoH & WHO