Posts Tagged SARS
MERS (Middle East Respiratory Syndrome) is the latest disease in nature’s little bag of tricks, which could turn into the next pandemic and solve our population issues for us. It is closely related to SARS (Severe Acute Respiratory Syndrome), both belonging to the same virus family. But, while SARS appeared in Asia, MERS first popped up in Saudi Arabia in 2012. Since then all cases have been seen either in the Middle East or in people who have travelled to the Middle East. As of June 2014 we have had 697 cases of which 210 people have died. As usual symptoms have been flu-like.
This is quite a high case fatality rate but, like bird flu, the virus has not raced around the world killing a third of the world’s population because it is not easily transferred from person to person, yet.
Any time one of these new diseases pops up it requires quite a bit of detective work to try and determine where it came from and how it works. It will probably come as no surprise that bats are once again implicated, the virus having been found in Egyptian tomb bats, a name guaranteed to generate sympathy with a nervous public.
Intriguingly the virus has also been found in camels, a situation which has some similarities with Hendra virus in Australia. Hendra virus lives happily in bats, infects horses (and kills them) and then spreads from horses to humans. However, as yet, there are no recorded cases of MERS causing disease in camels (although a number of camels have died in the UAE recently of undetermined cause, so this situation may change) and we have only recently seen the first confirmed case of a human catching the disease from a camel. Most of the other cases have been in people who have had very close contact with other sufferers. Where they caught it originally is still open to speculation.
It makes me think that the practice of veterinary medicine may be more dangerous than first thought. While we are all aware of the wonderful things we can catch from our primate neighbours no one really believed there was anything worth catching from our more distant cousins, like horses. Twenty years ago you would not have thought twice about examining a snuffly horse. Two years ago you would not have thought twice about examining a camel.
Australia has the largest feral camel population in the world, but no human cases of MERS. Preliminary testing of 25 camels has failed to find any evidence of MERS, implying that the Middle East camels may have been infected from the tomb bats or that the virus appeared in Middle East camels after the Australian population was established.
The upshot of all this is that we have absolutely no idea where the next fun plague might be coming from. As I get older and more paranoid I am becoming increasingly more nervous about travelling on crowded trains, planes and buses, full of sneezing and coughing people. And I am starting to think that sport is much more enjoyable when viewed from the comfort of my living room than from one of those packed sporting stadiums. I can see the day coming when I refuse to venture outside without my biohazard suit on.
Paranoia aside, most viruses are transferred between us via the things we touch, such as door handles, coffee cups, pens, etc. The best way to prevent this is by washing your hands frequently, with soap and water. To do it properly, sing the Happy Birthday song through twice while you are soaping up your hands. Oh, and don’t kiss bats, camels or any other non-human life forms. And maybe not even the human life forms.
Dr. F. Bunny
As I emerged from the aerobridge into the Manila terminal I noticed a woman pointing a weird device at me. It was a thermal camera, a gizmo used to measure skin temperature. High temperature areas show up yellow or red while low temperature areas are blue or purple. Given the current paranoia about things like bird flu and SARS this camera was being used to screen passengers in case someone had a fever, which could be indicative of an infection with one of these diseases. If you read the literature put out by the company that produces it (http://www.flir.com/cs/apac/en/view/?id=42362) they would have you believe that this is an effective screening process. But is it?
Thermal cameras have been used in veterinary medicine to detect lameness and abscesses by the heat they generate. You will no doubt have sprained something at some point and noticed how warm the area became, because of the inflammatory process. This is different to the central fever that is generated by infectious agents. According to the company’s literature the temperature in the corner of the eye most closely approximates core body temperature. The literature also states that “glass and plastic do not transmit infrared radiation, so people need to remove their glasses in order to be examined.” That’s me slipped through the net. The recommendation is also to scan individual passengers at a distance of 1 to 1.6 metres so that the face fills the screen. How this is possible for the mass of humanity streaming off the plane, where some people are looking ahead, others are looking to the side and still others are looking at the ground, is beyond me. However, this is more an operational fault than a fault with the camera per se.
A recent study attempted to objectively evaluate the effectiveness of thermal cameras in detecting fever. In this study all subjects that wore them removed their glasses and stood still in front of the device for two to three seconds, very different to the moving people at the airport. Using this method the thermal camera had a 90% sensitivity (10% of the people who had a fever were not detected) and an 80% specificity (20% of the people who were detected as having a fever did not actually have one) (Nguyen et al 2010). These figures were deemed to be acceptable even though it meant that some people escaped the surveillance net while others would be falsely detained. Still no system is 100% fool-proof.
What also puzzles me is what the authorities would have done if they had registered a positive. Presumably that person would have been asked to stand aside for further investigation, but what of the other passengers? Would all the previous passengers, who had by now dispersed through the terminal, be rounded up? Would all the passengers yet to emerge from the plane be detained? Surely if one person had a fever then all the passengers and crew would need to be regarded as infected, as we had all been breathing the same air for the past however many hours? Veterinary medicine is much more straightforward and logical. Any animals shipped overseas need to have a defined set of vaccinations beforehand (e.g. rabies if coming from a rabies endemic country) and they enter a period of isolation after arrival at their destination. If they are healthy at the end of this quarantine period they are free to go. This is of course completely impractical for people, who like to jet-set around the world on a daily basis. However, it certainly does enhance the potential for diseases to spread rapidly around the world as we saw with SARS, which travelled at the speed of flight from Asia to Canada.
The other problem with thermal imaging is that it only detects infected people who have a fever. Many diseases, such as bird flu, have an incubation period of several days during which the infected person displays no clinical signs but is still potentially infective.
I don’t know what the solution to averting a pandemic is, possibly a combination of individual country surveillance of people and animals coupled with vaccination. Infrared thermography has a potential role to play but only if used properly and not in the haphazard manner I saw in Manila. Unfortunately this would add to passenger inconvenience, which would, however, be a small price to pay if it might avert or mitigate a pandemic.
Dr. F. Bunny
Nguyen, A.V., N.J. Cohen, H. Lipman, C.M. Brown, N.A. Molinari, W.L. Jackson, H. Kirking, P. Szymanowski, T.W. Wilson, B.A. Salhi, R.R. Roberts, D.W. Stryker, and D.B. Fishbein. 2010. Comparison of 3 infrared thermal detection systems and self-report for mass fever screening. Emerging Infectious Diseases 16: 1710-1717.
Zoos exist to save people money spent travelling to exotic places to see animals in the wild. By bringing a large number of species together in a small space people get a snapshot of the world’s different biomes. Pity the archaeologists of the future digging through the remains of Melbourne, Los Angeles and London, wondering how elephants, tigers and monkeys could have been native to all three cities.
While it’s certainly “nice” to see polar bears in Melbourne, they don’t appreciate the summer heat any more than the gorillas in Toronto enjoy the snow. This mixing and matching produces all sorts of husbandry and dietary problems, which are handled with varying degrees of success. It also creates novel disease issues. This was highlighted recently by the deaths of four polar bears in a German zoo (Greenwood et al 2012). They died of a herpesvirus infection contracted from the zoo’s zebras. The herpesvirus was perfectly well adapted to the zebras and caused them no problems but, when it got into a naïve, non-adapted polar bear, fatal illness was the result.
Herpesviruses seem particularly good at this sort of thing. African elephants carry a herpesvirus that is fatal to Asian elephants. Wildebeest carry a herpesvirus that kills other species of hoofstock. Squirrel monkey herpes kills owl monkeys. A herpesvirus carried by South American conures kills African and Australian parrots. SIV, a relative of HIV (and not a herpesvirus) carried by African monkeys, kills Asian macaques. Normally this would not be a problem as these animals, and their bugs, would not come in contact with each other. However, this mixing of animals from different areas, which gives adapted viruses and bacteria access to non-adapted hosts, is occurring more and more.
Not only is this a problem in zoos but it is happening in the big wide world too. As we clear more and more habitat we come into contact with new species and new disease agents. Feral species, which have made their way into new habitats because of our deliberate or accidental influence, bring their bugs with them too. Species that previously had no connection with each other are suddenly brought into close proximity. Hence, the transmission of Hendra virus from bats to horses, Nipah virus from bats to pigs, toxoplasmosis from feral cats to marsupials and otters, monkeypox from Gambian giant rats and prairie dogs to humans, and chytridiomycosis from African clawed frogs to the amphibians of the world.
At least, when animals are concerned, some of these diseases can be confined to farms or contained by quarantine measures. These are, however, not always as effective as we would like as seen by the introduction of foot and mouth disease to Great Britain, equine influenza to Australia, and psittacine pox to New Zealand. These diseases were eradicated at great expense and effort.
Unfortunately people don’t go through quarantine when they travel, allowing for extremely rapid dissemination of diseases. Just look at how quickly SARS spread from South East Asia in November 2002 to Canada by April 2003. It is estimated that a flu outbreak in the northern hemisphere will reach Australia in four to eight weeks. While we impose travel restrictions on animals to safeguard our pets and agriculture we certainly don’t want to inconvenience ourselves by impeding our own travel, even though the consequences are potentially far more catastrophic. While globalization has facilitated trade, democracy, entertainment, and the dissemination of information, it has also greatly enhanced our ability to spread disease. Unfortunately the science of predicting what the next possible pandemic will be and where it will come from is at a similar stage as the science that predicts earthquakes and volcanic eruptions i.e. we have absolutely no idea. For the moment all we can do is react and hope that will be enough.
And don’t forget to keep washing those hands.
Dr. F. Bunny
Greenwood, A.D., K. Tsangaras, S.Y.W. Ho, C.A. Szentiks, V.M. Nikolin, G. Ma, A. Damiani, M.L. East, A. Lawrenz, H. Hofer, and N. Osterrieder. 2012. A potentially fatal mix of herpes in zoos. Current Biology http://dx.doi.org/10.1016/j.cub.2012.07.035.