Worrisome or even frightening outbreaks of mysterious infectious diseases are not new. Two such outbreaks, one of Ebola and one of MERS-CoV now underway in Africa and the Middle East respectively are of special concern.

Upsurge in Cases

The mysteries surrounding MERS- CoV have only deepened in the past few weeks as the cases have increased dramatically. There is no convincing explanation yet for the sudden increase in cases. According to Marjorie Pollack, Deputy Editor of ProMED, a listserv used as an informal surveillance system, “Two years since the first news reports, MERS remains a mystery. With more cases reported in a single month than in the two years combined, no one is certain how people become infected.”

 ProMED has been instrumental in bringing new infections to public attention since 1994, notably both SARS in the early 2000’s and most recently the first MERS notices were posted to ProMED.

Case Count

The latest report from the World Health Organization on May 23 describes 635 laboratory-confirmed cases of infection with MERS-CoV, including 193 deaths for a case-fatality rate of 30%. The WHO notes that 41 laboratory confirmed cases were reported just between May 10-15 from Saudi Arabia.

International Concern

International concern about the seriousness and urgency of the situation is high, but not high enough at the moment to convince an International Panel advising WHO to declare a state of emergency. This judgment is likely to persist as long as evidence of limited person to person spread holds up.

Not everyone agrees with the WHO panel,  Preben Aavitsland, a Norwegian epidemiologist who helped draft the regulations about outbreaks told Science Insider, “I personally think from the information publicly available that the event should be declared a PHEIC (Public Health Emergency of International Concern).

There are certainly multiple reasons to be concerned. There is a potential threat posed by the large number of pilgrims estimated at 6 million per year who make their way to Saudi Arabia from all over the world. It is possible that some infected pilgrims could return to less developed countries where detection of importations might be delayed and infection control procedures might be too limited to snuff out the cases before transmission becomes widespread. According to sources who spoke with The Epidemiology Monitor, public health officials may be more worried than they are admitting to publicly.

The long list of unknowns about MERS transmission coupled with any new evidence of enhanced spread would likely trigger an emergency declaration. For now, the international advisors are calling for more studies on how the virus spreads. For example, there has been no case-control study to identify risk factors of transmission.

Criticisms

The Saudis have been criticized in many quarters for not being as forthcoming as possible about the epidemiologic facts surrounding each of the cases. As noted in a WIRED magazine article, “Restrictive government can still put the whole world in danger by clamming up. That’s because the most important factor in controlling epidemics isn’t the quality of our medicines. It’s the quality of our information.”

Scientific Competition

In addition to the lack of cooperation from Saudi officials, there has been the lack of collaboration among scientists and other investigators.  In an article entitled “Triumphs, Trials, and Tribulations of the Global Response to MERS Coronavirus, Scott McNab and colleagues note that the “…meaningful collaboration that helped the scientific community to rapidly identify the SARS coronavirus has not been seen recently. Collaborative research into MERS coronavirus has been scarce, with investigations marked by bitter disagreements between public health authorities and scientists about the virus’ discovery and the ensuing publications, processes, and patenting of products.”

Unsolved Mysteries

Among some of the key unsolved mysteries surrounding the Saudi outbreak are the following:

1. The current increase in reported cases is partially related to nosocomial

transmission, according to Pollack, but not all of the cases can be explained through this route of transmission.  And even for the nosocomial cases, it is unclear if transmission is occurring through droplet spread, aerosolization, or perhaps fomites.

2. Camels are considered the most likely intermediary host and fruit bats (Egyptian tomb bat: the possible reservoir, yet many case have occurred in city dwellers.  How can one explain this discrepancy ?

3. Camels have antibodies to MERS, but came handlers, butchers, and other with close contact with  the animals are not a higher risk than persons with no contact.

4. The dramatic increase in reported cases suggests that genetic changes may have made the virus spread more easily, however experts in genetics disagree saying there is no evidence of genetic change or that the genome is too complex to know what mutations to look for.

5.  There are almost 50 times more camels in Africa than in the Middle East according to one estimate from the Food and Agriculture Organization and camels from Africa have tested positive for MERS-CoV.  However, there have been no reported cases from Africa.  A report that the virus was detected in camels as far back as 1992 only deepens the mystery of  why the outbreak is occurring now.

As reported in Science, several potential explanations for the upsurge have been put forth such as increased testing for MERS, genetic changes to make the virus more transmissible, poor infection control with an accompanying seasonality in case reports.

According to Ian Lipkin, John Snow professor of epidemiology at Columbia University, an increase in the number of reported cases is not equivalent to an increase in the number of actual cases. It may reflect better case ascertainment, he noted in an article for CNN. This is basically the argument that increased testing accounts for the recent upsurge.

Ebola Virus Outbreak

The Ebola virus outbreak has been focused in Guinea which has reported 258 clinical cases including 174 deaths representing a case fatality rate of 67% for reported clinical cases as of May 24. Suspect cases have occurred in neighboring Sierra Leone and in Liberia where 11 of 12 reported cases have died. Much is known about Ebola. It is transmitted via direct contact with bodily fluids from an infected person. This happens most readily for hospital caretakers of infected persons or from exposure to fluids during medical procedures. However, this is the first time Ebola has been reported in West Africa and the mystery of why it is occurring or being reported now is unsolved. ■

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