Keystone Symposia: Bats, camels and emerging viral disease from the Middle East
October 2, 2013
Many of you may recall the spring of 2003 when the world held its breath as a new and deadly virus called SARS emerged. The virus, so named because it caused Severe Acute Respiratory Distress Syndrome, or SARS, had spread from the Far East to countries around the globe with alarming speed. A particular virus hotspot was Toronto, Canada, where 251 cases were reported with 43 deaths. Fortunately, the virus was limited in its ability to spread from person to person, and careful hygiene and quarantine procedures were able to stop it in its tracks. When the outbreak ended in 2004, most of the world had dodged a bullet, though one that did kill 774 people.
The SARS outbreak tested global health authorities. Although their response was not perfect, their ability to identify the virus, determine appropriate containment and recommend treatment options was a stunning success. It also served as a practice run for future outbreaks from new pathogens that may prove to be more problematic than the SARS coronavirus ultimately turned out to be.
Today, the world faces a new threat sure to test global response networks. The so-called MERS (Middle Eastern Respiratory syndrome) virus is a new human pathogen beginning to spread from its Middle Eastern origin. Like the SARS virus, the MERS virus also infects the respiratory tract and can cause severe acute pneumonia and renal failure, often with a fatal outcome. Most cases have occurred in Saudi Arabia, Jordan, Qatar and the United Arab Emirates, but infection has also been imported by sick travelers to Tunisia, the United Kingdom, Italy, Germany and France. To date, there are 130 laboratory-confirmed cases of infection with MERS; 58 patients have died.
You may be wondering where these new deadly pathogens originate? In most cases, it is apparent that newly emerging viruses have their origins in other animal species. Typically, a virus that is well adapted to its host species and is not particularly lethal will learn to infect a new (in this case human) host, often with very lethal consequences. In the case of SARS, the virus was found to be a resident of bats that had probably learned how to infect humans through an intermediary host. Other classic examples of animal viruses triggering new infections in humans include the AIDS virus (derived from chimpanzees and gorillas), Ebola virus (derived from fruit bats) and influenza (derived from aquatic birds).
But what about MERS? The virus is so new that scientists are still in the early stages of identifying its animal origins. However, recent studies have indicated that viral genetic material isolated from the feces of an Egyptian tomb bat was identical to the genetic sequence of the virus present in a Saudi Arabian MERS victim. While promising, the sequence tested was too short to allow a definitive identification. In addition, although researchers felt that bats may be the primary source of the virus, there are too few bat-human encounters to explain the frequency of observed cases, possibly implicating an intermediate host. The answer to this puzzle may be the camel. Researchers have now found that the blood from some Middle Eastern camels contains antibodies specific for the MERS virus. Although no virus was found in the animals tested, the antibodies indicate that the animal had made an immune response to an earlier encounter with the virus. In other words, it is beginning to look as if bats are infecting camels with MERS and that the sick camels are then infecting humans. Camels make sense as an intermediary host since they have considerable contact with humans in the Middle East — camel farms are common and camel racing is a popular sport. Further research will be necessary to nail down the transmission patterns of the MERS virus.
In the meantime, considerable efforts are underway by many national and international organizations to contain the MERS outbreak. Foremost in this effort is the Global Outbreak Alert and Response Network, a collaboration of more than 150 organizations, networks and institutions involved in the rapid identification, confirmation and response to outbreaks of new infectious diseases. The primary approach consists of rapid reporting and the implementation of specific infection prevention and control mechanisms in health care facilities providing care for suspected MERS patients. There is every confidence that this latest threat to global health will be contained.
I'll be talking more about MERS and other emerging viruses at a free community forum on Wednesday, Oct.2 at 7 p.m. at the Silverthorne Town Pavilion. I look forward to seeing you there.
David L. "Woody" Woodland, Ph.D. is the Chief Scientific Officer of Silverthorne-based Keystone Symposia on Molecular and Cellular Biology, a nonprofit dedicated to accelerating life science discovery by convening internationally renowned research conferences in Summit County and worldwide. Woody can be reached at 970-262-1230 ext. 131 or firstname.lastname@example.org.