SARS - More Questions Than Answers

by Maurice Mckeown, BDS, PhD
(our New Zealand correspondent)

What is SARS?
SARS stands for Severe Acute Respiratory Syndrome. The organism concerned primarily attacks the lungs. Victims develop a high fever, headache and dry cough followed by shortness of breath. Approximately 20- 25% of patients go on to develop pneumonia and some of those die. You are much more likely to die if you have another medical condition or are over the age of 40. Remarkable progress has being made in the last few weeks by research laboratories worldwide.

How can scientists have made so much progress so quickly?
Very recent advances in genetics have made it possible to compare suspect organisms with others. This is done by matching fragments of genetic material. Newly developed biological chips are now being used for diagnosis. They contain hundreds of fragments of known viruses. The chip is exposed to fluid containing the suspect organism and any match-ups of genetic material can be detected using laser-scanning technology. Initial work at the University of California at San Francisco, suggested that the culprit is a corona virus. Then a Vancouver research team mapped out the entire genetic sequence of the virus in just 6 days. Now many more research teams are completing the genetic map of their virus samples. The WHO (World Health Organisation) has designated a dozen or so labs around the world to work together on the problem. They have been co-operating in unprecedented fashion, rapidly exchanging information via the Internet.

What has been achieved so far?
The WHO now has enough evidence to definitively state that a corona virus is responsible. It is not a currently known variety. The corona virus family can infect animals and people. They are responsible for possibly 30% of colds and can also cause diarrhoea, particularly in children. No one is sure where this 'new' virus came from. Many of the earliest victims in Southern China had links to animals and food. The best current guess is that the virus previously lived in an animal species and has somehow been able to jump the species barrier to be able to infect people. The best candidate animals seem to be birds, pigs or cows. The WHO also believes that the virus can be held solely responsible for the disease. In other words they do not think it needs any help from other viruses or bacteria to cause the syndrome. Some scientists are not convinced. A few even doubt that the corona virus is the culprit. Some medical researchers think that other kinds of viruses (some have been found in samples from infected people) may be present in some of the more severe cases. Chinese scientists are claiming that a Chlamydia bacterium is also involved.

Where did the SARS virus come from?
Comparisons of the genetic map of the virus with the map of other human and animal corona viruses has lead researchers to conclude that it is so different from others that it could not have arisen by a mutation of another known type. Scientists in China have now found strong evidence that the SARS virus, or one very close in structure, is present in three species sold for food consumption - the palm civet, the racoon dog and the badger. It is not yet clear if one, or all, is the primary infection source. Currently the civet is the front- runner. It is said to excrete large amounts of the virus in feces, urine and breath. All are carnivores and could have been infected by eating another mammal. The masked palm civet is reputed to be a good rat hunter. A number of people who handle civets have also tested positive for the presence of antibodies. Much work has yet to be done however.

How do you get SARS?
It was initially thought that close contact with a victim was necessary. Initially a few individuals infected a large number of medical personnel. It is believed that the virus is transmitted in droplets of fluid expelled by coughs and sneezes. WHO epidemiologists have now concluded that the virus is transmitted almost entirely by large droplets reaching the mucous membranes of nose and lungs and not by feces or urine reaching the mouth. Only in rare circumstances are other transmission methods involved. It has also become clear that some victims are super infectious and can infect large numbers of people. No one knows why. Some authorities believe genetic factors may be involved.

When a Hong Kong high rise suffered an outbreak, it posed new questions about how the virus spreads. Investigation of the outbreak revealed that one visitor to the building infected 321 residents. The Hong Kong health authorities have done an extensive investigation. Their published report concludes that the virus was spread primarily by a poorly designed and maintained plumbing system, which resulted in an aerosol transmission of virus from a cracked sewer pipe. It is known that corona viruses are excreted in urine and faeces. They are also present in other body fluids. Other modes of transmission may also have been involved in the high-rise outbreak.

What symptoms are found in someone incubating SARS?
Almost all patients have a fever and many have associated symptoms like headache, chills, muscle aches and general malaise. Although SARS is universally thought of as a respiratory condition this is not strictly true. In a study of over 1600 cases in Hong Kong it was found that only 61% showed respiratory symptoms. Most of the others (32%) had vomiting and diarrhoea. It is well known that animal corona viruses commonly affect the GI tract or the respiratory system. It is not clear why the course of the disease varies in different people.

Could someone get SARS from a blood transfusion?
Authorities are not completely sure. Genetic material from the virus has been found in the blood of sufferers. Many blood transfusion services are imposing restrictions on donors who have visited infected regions or who may have been quarantined because of contact with an infected person. Currently the WHO recommends that blood not be taken from anyone who has visited a SARS affected area with local recent transmission, until 21 days after they return home. Similar rules apply to quarantined individuals.

Can the virus be picked up by touching objects like door handles, elevator buttons or keypads?
Until recently it was thought that the virus could only survive on a dry surface for a short time possibly an hour or two. Now tests done by the CDC (Center for Disease Control) in the US - have shown that the virus can live for at least 24 hours. Other labs familiar with animal corona viruses say that some can live for many days in such circumstances. They become reactivated when exposed to moisture.

Can SARS be transmitted in an airliner?
Yes that is possible. I think it is worth quoting in some detail from a recent WHO analysis of the problem as the issue potentially affects many of us. WHO reports "The number of flights during which transmission of SARS may have occurred remains at four. The total number of cases resulting from exposure during these four flights has been revised to 27. One flight alone, CA112, which flew from Hong Kong to Beijing on 15 March, is now know to have accounted for 22 of the 27 cases. WHO is aware of an additional 31 flights with symptomatic probable SARS cases on board. No evidence indicates that in-flight transmission occurred on any of these flights. No flights have been implicated in the transmission of SARS after 23 March 2003. Complete data on seating information for all cases has not been obtained. However, it is now known that, on one flight, persons sitting seven rows in front and five rows behind a person with symptomatic SARS developed the disease. WHO is aware of four flight attendants, two of which were on the CA112 flight, who have become infected"

The risks are clearly extremely low overall, but if you sit fairly close to an infectious person you could be infected. There is some controversy about the ability of cabin air filtration systems to catch virus particles in the generally circulating air. Questions have also been asked about the maintenance schedules for such filtration systems. Air from toilets is vented directly outside and is not re-circulated. The ideal situation would be for all cabin air to be expelled: thus avoiding re-circulation. Airlines say that would cost too much. The UK based Aviation Research Institute claims that adopting the procedure would cost 20c per passenger per hour. Are you willing to pay the extra couple of dollars?

It has to be said however that only a small number of aircrew have come down with the infection, and proportionally even fewer passengers have contracted SARS. Some airlines have now implemented more stringent disinfecting procedures, even issuing masks on some routes. Perhaps you should ask your favourite airline just what they are doing to help keep you safe.

Is it of value to wear a mask in public?
It is probably of very limited value unless you are the sufferer who is trying to avoid passing the virus to others. If masks fail to seal perfectly to the face, air is drawn in via the gaps instead of through the mask. A beard places one at a substantial disadvantage. Some authorities believe that moisture build up renders a mask useless in minutes rather than hours.

What is the incubation period?
It seems to average about 3-5 days. Although instances of a 10-14 day incubation period are known and slightly longer periods suspected to occasionally occur. It is not known with certainty when a sufferer becomes infectious; although it is assumed to be when they become unwell and develop a dry cough and fever. The unpleasant possibility of the existence of apparently healthy carriers has not been ruled out.

Has a diagnostic test been developed?
Yes - a number of labs around the world have developed rapid tests which provide results in an hour or two. These tests are based on the ability to identify the genetic material specific to the virus. They are currently being refined and commercial versions for wide distribution will be available very soon. At present they appear to be too unreliable for widespread use. An accurate diagnostic test will be very valuable because at present SARS can only be excluded by finding out that a patient has another known condition. Another kind of test, one for the presence of antibodies, has been developed. It identifies that the body has responded to the SARS infection. It will only be useful as a way of checking if a person has had previous exposure to the virus. It is believed that it should provide a valid reading about 21 days after the disease has begun.

How long will it take to develop a vaccine?
In theory a vaccine seems possible in a very short time. Health authorities are however very reluctant to release a vaccine to large numbers of people without thorough testing. Some say a vaccine could be available in a year, others are projecting a 3-5 year time frame. There is also the problem of producing millions of doses to inoculate very large numbers of people.

Is there a drug to cure SARS?
Sadly no -- Some antiviral drugs plus steroids, have been tried with very limited success. A US lab is currently testing 2000 available drugs in the hope that one may be able to attack the virus. If this effort fails a new drug will probably be developed. But it is likely to take years to do so. Some researchers are now trying to tailor AIDS drugs to combat the corona virus. Possibly the most promising approach could be the use of protease inhibitors. Proteases are essential to the mechanism by which a virus exits a cell which it has infected. Protease inhibitors block specific proteases and thus prevent a virus from leaving a cell. They do not appear to affect normal cell function. A German research team at the University of Lubeck has discovered that a protease used by other cold viruses is almost identical to the one used by the SARS virus. An inhibitor for the cold virus protease is already in the final stages of testing. It probably won't work for SARS without modification. The German researchers believe that only a slight modification may be needed to create a SARS-compatible version. In the meantime Hong Kong doctors are trying a protease inhibitor cocktail approved for use in AIDS patients.

Will SARS eventually disappear or become harmless?
It may become much less dangerous, no one knows. The chances of it disappearing forever are remote. Canadian researchers have found evidence of its presence in 20% of apparently healthy people from Asia. If this is confirmed it means that the virus is already present in substantial numbers of people who would act as a reservoir for future infection. If it normally exists in an animal population the same applies. It may become like other respiratory viruses and pop up intermittently in the winter season just like flu. The WHO now believes that the virus will appear again next Northern Winter even it subsides now. We have a new disease to contend with.

What happens if the virus changes just like the flu?
This is a major fear for doctors. There may already be some evidence that it is changing. The death rate is rising slightly and the residents of the Hong Kong high rise were much sicker than other victims. Autopsies on some of those victims have revealed damage to many organs outside the lungs. Doctors don't know whether this represents a more severe infection. It could unfortunately also be the result of inappropriate medical treatment. Genetic sequencing of the virus is now being completed in many labs around the world using different virus samples. Initial comparison between Canadian and US virus samples gave an almost identical result. These new efforts around the world should provide a clearer picture about how variable the virus is and whether it is changing over time. At present it seems that there is little variation in strains in different parts of the world, but virologists say it is early days!

How can the spread of the virus be stopped?
The best approach appears to be rapid isolation of suspects and the quarantining of their close contacts. Taking daily temperatures is being widely used in Singapore. That technology savvy society has now come up with a credit card style thermometer which is pressed unto the forehead to give a reading in 5-10 seconds. In Singapore 80% of victims have not passed the disease on to anyone else. A few incubators have spread the disease widely in a number of countries. Unfortunately quarantine procedures in Hong Kong, Singapore, Taiwan and Toronto have been less than perfect. Some people do not obey instructions. Singapore now has an automatic heavy fine in place. Electronic tags and surveillance cameras are also being used. In Toronto legal action is being taken against a few people who have not complied with official directives. Some regions are having major successes. Vietnam may have completely arrested the spread of the disease and Singapore has had no healthcare workers infected for over three weeks. In China the practice of eating animals likely to carry the virus must stop. The import of civet meat into Hong Kong has now been banned.

Is the virus more dangerous than other deadly diseases?
Some diseases are much more deadly. e.g. AIDS in which the mortality rate is ultimately very high. Ebola fever has a death rate of over 50%. On the other hand many diseases have a much lower mortality: Cholera 3-4%, the 1918 Spanish Flu estimated at 1-3% and malaria at 1-2%.

If I get SARS what is the chance of dying?
The good news is that as many as 80% of sufferers get better without developing pneumonia. If you are young and healthy your chances are very good. Unfortunately for reasons unknown, some people get pneumonia and need to be treated in intensive care. The WHO says that the death rate is now about 5% but rising. This sounds reassuring but Dr Henry Niman, a Harvard professor, thinks they are wrong. He says their statistics are unsound. They are comparing the number of people who die with the number of people who currently have the disease. They should, he contends, be comparing the number who die with the number who get better. The official system is a bit like working out the match statistics before the game is over. Unfortunately the time between contracting the disease and dying is from 14 days to 8 weeks. By Dr Niman's reckoning the current death rate (second week of May) in Hong Kong is 18.25%, in Singapore it is 13.8% and in Canada18.2%. Sobering news indeed.

Mortality is very closely linked to age. Below the age of thirty it is very low. From 40 to the age of 55 the death rate is about 8%. After that it climbs steeply. Mortality statistics are complicated by the existence of other medical conditions. Hong Kong authorities say almost 70% of those who have died had other medical conditions which may have contributed to their deaths.

Whichever figures you choose, they only apply to the current situation. Future trends are pure speculation. If however the current rate of spread continues, we are faced with some sobering possibilities. Currently the number of cases is doubling every 24 days. The number of deaths is doubling over a 14-day period. If such trends continue unchanged, year's end would see millions of cases worldwide.

What is the best way to stay healthy?
Ultimately our immune systems are the best defence. All the usual advice applies. Eat a healthy diet, get enough sleep and try to avoid stress. A good multi vitamin pill might help. There are many herbs and potions that many swear by. It might also be useful to suck zinc lozenges at the first signs of feeling unwell. Zinc is known to be helpful in minimising the effects of cold viruses. A zinc nasal spray is currently being tested with promising initial results. It is also known that selenium deficient animals are more prone to certain viruses. A selenium supplement might be helpful.

Personal hygiene is very important. All authorities recommend regular thorough hand washing. If you are out and about the best plan is to carry an antibacterial hand gel. These alcohol-based rubs are carried by most pharmacies. You don't need water, so there is no necessity to dry your hands. Those air hand driers in public washrooms appear to be an excellent mechanism for blowing infected material all over the place. Tests have shown alcohol gels work much faster and better than anti-bacterial soaps. Hong Kong authorities have advised pressing elevator buttons with your car keys. (Automatic bank teller machine could require a little practice.) They also advise closing the toilet lid prior to flushing and recommend daily cleaning with a dilute bleach solution applied to toilets and all surfaces possible, particularly items like telephones. It may be necessary to wrap some computer keyboard in cling wrap.

If you have just returned from overseas, get sick and think that you might have SARS what should be done?
Contact your doctor or hospital by telephone and ask for advice. Do not use public transport or a taxi to seek help.