Lawrence LeBlond for redOrbit.com – Your Universe Online
Over the past weekend, the World Health Organization (WHO) has been informed of four additional laboratory-confirmed cases of infection with Middle Eastern respiratory syndrome coronavirus (MERS-CoV). The new cases may actually come as no surprise to an international group of experts who reported last week that the disease may become a “slowly growing epidemic.”
Publishing a paper in The Lancet Infectious Diseases, the researchers have estimated that at least 62 percent of MERS cases have gone undetected, likely due to many cases being mild and not requiring hospitalization. Furthermore, surveillance efforts are geared toward the most severe cases. The research team also said it is unclear whether the disease can sustain human-to-human transmission without a recurrence of animal infections.
The scientists, hailing from Imperial College London, the University of Edinburgh, and the Institut Pasteur in Paris, have gathered data on 111 of the confirmed and probable cases that have been identified through August 8 of this year.
According to CIDRAP’s Robert Roos, the team followed four cases that occurred in visitors to Jordan, Qatar, Saudi Arabia, and the United Arab Emirates to work out an estimate for the number of undetected cases of MERS. Using these cases, they then calculated the average length of their visits and then noted that that each of the visitors had passed the virus to one or two other people after returning home from their visit.
Assuming that the per-day risk of infection for the visitors was the same for residents in the countries visited and taking into consideration the number of reported cases in the Middle East, the researchers estimated that the number of symptomatic cases of MERS up to August 8 was about 940. The researchers said based on this calculation, at least 62 percent of cases have been missed.
The research team also used MERS-CoV genetic data to estimate the total number of infections in both animals and humans.
Utilizing a method that involves taking estimates of the growth rate of the viral population derived from charting the diversity of genetic sequences, the team estimated that 17,940 infections occurred in both humans and animals between March 2012 and August 8, 2013. Based on their calculations, the team said the virus is continuing to spread, but it is unclear how much of the transmission is in animals and how much is in humans.
“Both the analysis of the genetic sequences and of the epidemic curves suggested that an epidemic is underway either in an animal reservoir or in man. These analyses do not allow us to distinguish between these scenarios and to determine whether MERS-CoV is currently self-sustaining in man,” the researchers said.
If there is an epidemic currently going on in humans, the team note that, given the current low estimated reproduction rate, it is likely that public health measures are sufficient to contain the spread of the disease and reduce morbidity and mortality.
Based on the team’s estimate of missed cases, the current mortality rate is likely at the high end of the clinical spectrum, meaning that far fewer people are dying from the disease than is reported. Currently, the mortality rate for confirmed cases stands at about 42 percent. If the scientists’ estimates of 940 cases through August 8 is accurate, then mortality rates would drop exponentially.
In the latest WHO reports, Saudi Arabia’s Ministry of Health has stated that a previously laboratory-confirmed MERS-CoV patient has died along with an additional new death, bringing the total number of deaths related to the disease to 66.
Additionally, the MOH has confirmed four new cases of MERS, bringing the total number of cases to 157.
The new cases include a 75-year-old man from Oman with underlying medical conditions who became ill on Oct 1 and died on Nov 10; a 61-year-old man from Qatar with underlying medical conditions who became ill on Nov 4 and was hospitalized on Nov 7, currently in critical condition; a 47-year-old man from Kuwait who became ill on Oct 30 and was hospitalized on Nov 7, currently in critical condition; and a 52-year-old man from Kuwait with underlying medical conditions who became ill on Nov 7 and was hospitalized on Nov 10, also currently in critical condition.