The World Health Organization (WHO) said in a report today that the continuing outbreak of Middle East respiratory syndrome coronavirus (MERS-CoV) cases is probably being sustained, as some researchers have suggested, by a combination of human-to-human transmission and spillover from animals or other non-human sources—not one or the other.
In its latest summary and literature update, the WHO also agreed that many MERS-CoV cases are probably going undetected and warned that this poses a risk of further outbreaks in hospitals.
The agency's current MERS-CoV count is 157 confirmed and 19 probable cases, for a total of 176. With 69 deaths, the case-fatality ratio is 39.2%. Two cases recently reported in Spain remain in the "probable" category, pending completion of testing.
Most recent cases sporadic
Since the WHO's last summary on Sep 20, 27 new MERS-CoV cases have been reported, and three countries have had their first cases: Kuwait, Oman, and Spain. Eighteen of the 27 cases were sporadic, meaning the patients had no contact with other known cases, the WHO said. Another 7 case-patients reported contact with others, and information was lacking for the other 2 cases.
"This appearance of the virus in new countries and the steady increase in sporadic cases continues to raise concerns about possible expansion of virus in the as yet unknown reservoir," the WHO said. "It is clear that human-to-human transmission is occurring. However, the continuing of reports of sporadic cases from Middle Eastern countries suggests that cases continue to be infected from non-human source(s) as well."
The statement added that the two probable cases in Spain are the only ones reported in people who participated in this year's Hajj in Saudi Arabia. The cases involved two women who traveled together and have since recovered. In a statement today, Spain's health ministry said the follow-up period for monitoring the two women's contacts expired yesterday without detection of any more cases.
"The public health alert is now considered closed," the ministry statement said.
In other observations, the WHO said, "MERS-CoV surveillance is focused on severe disease in much of the Middle East and it is likely that many milder cases are undetected." This echoes the conclusion of a recent study in which researchers estimated, on the basis of cases related to travel to the Middle East, that at least 62% of symptomatic MERS cases have gone unnoticed.
Risk of hospital outbreaks
Undetected cases can spawn hospital outbreaks, the WHO warned. "The large number of transmissions that occur in hospitals raises concerns about transmission occurring in this setting when infection with MERS-CoV is not recognized either because cases are not tested or the tests are falsely negative," the agency said. It noted that upper respiratory samples can yield false-negative results and that lower respiratory specimens are more reliable.
The agency made several recommendations to help prevent hospital outbreaks of MERS-CoV. Among them is that countries in the affected region should consider testing community-acquired pneumonia patients even if they are not severely ill.
Possible animal sources
In developments related to the mystery of the virus's source, the agency said all four recent case-patients in Qatar had contact with farm animals. The first case involved a 61-year-old Qatari who owns a farm, and the second case was in a 23-year-old resident who worked on the farm.
The third and fourth cases involved a 48-year-old man and a 61-year-old man who had had no contact with other cases but had "frequent interactions with farm animals," the WHO said. It added that Qatar's Supreme Council of Health is investigating the animal exposures of all four patients.
Meanwhile, a Kuwait News Agency (KUNA) report today, citing Qatari health officials, said the 48-year-old MERS patient in Qatar died of his illness yesterday. This appears to contradict a machine-translated Nov 19 KUNA report, which said a 48-year-old patient in Qatar had recovered. The same Nov 19 KUNA story said a 61-year-old who was a foreign visitor in Qatar had died.
As for the possibility that camels are the source of the virus, the WHO today repeated the cautious view it expressed in a set of frequently asked questions earlier this week. It said the recent finding of the virus in a camel owned by a Saudi Arabian MERS patient is consistent with earlier findings of MERS-CoV–reactive antibodies in camels and is important information.
"However, this finding does not necessarily implicate camels directly in the chain of transmission to humans," the agency said. "The critical remaining question about this virus is the route by which humans are infected." It also noted that most of the patients in sporadic cases were not exposed to camels.
CIDRAP staff member Carlos Cruz provided translation assistance for this story.
Nov 22 WHO MERS summary and literature update
Nov 18 CIDRAP News story on cases in Spain
Nov 19 CIDRAP News story covering WHO FAQ advising caution on camel link
Spanish health ministry press releases
Nov 14 CIDRAP News story on study indicating suggesting many undetected cases