Initially when the new infectious disease SARS (Severe Acute Respiratory Syndrome) emerged early indicators were that it was not easily transmissible. The first indication that it might be more easily transmitted was the discovery of its transmission from one doctor to several people who stayed on the same floor of the Metropole Hotel in Hong Kong. As SARS continues to spread a consensus is emerging that SARS is much more easily transmissible than originally thought. Suspicions that it is caused by a coronavirus strengthen this belief because about one third of all colds are caused by coronaviruses and of course colds are fairly easily transmitted.
The Hong Kong Department of Health has today issued an unprecedented isolation order to prevent the further spread of Severe Acute Respiratory Syndrome (SADS). The isolation order requires residents of Block E of Amoy Garden to remain in their flats until midnight on 9 April.
The decision to issue the isolation order was made following a continued steep rise in the number of SARS cases detected in the building over the past few days. Concern about a possible outbreak in Amoy Garden mounted on Saturday, when 22 of Hong Kong’s 45 new SAR cases hospitalized that day were determined to be residents of the estate. On Sunday, 36 of the 60 new patients admitted to hospital with probable SARS were Amoy Garden residents.
Hong Kong health authorities today informed the public that a cumulative total of 213 residents of Amoy Garden had been admitted to hospital with suspected SARS since reporting on the disease began. Hong Kong’s outbreak began on 12 March when health officials first recognized a cluster of cases of atypical pneumonia in the Prince of Wales Hospital.
Of the 213 Amoy residents affected in the outbreak, 107 patients resided in Block E. In addition, most of these 107 patients from Block E lived in flats that were vertically arranged.
This suggests that SARS may be spreading in Hong Kong according to a different pattern, still involving close person-to-person contact with bodily secretions from an infected person. WHO epidemiologists are considering the possibility that bodily secretions containing the causative virus might somehow enter common systems that link rooms or flats together. This pattern of spread would be in addition to the well-documented face-to-face contact that has been seen in the majority of cases reported so far.
Earlier this month, Hong Kong epidemiologists detected an unusual pattern of transmission among guests and visitors at the Metropole Hotel during the critical period of 15 to 23 February. Guests and visitors at a single floor of the hotel are thought to have spread SARS to Toronto and Singapore and to have started the outbreak in Hong Kong’s Prince of Wales Hospital. No staff at the hotel developed symptoms
The guests of the Metropole Hotel who got SARS all stayed on the same floor of the hotel. This again suggests spread of the disease via air ducts.
If ducts in the Amoy Garden building are spreading SARS then quarantining the people of that apartment building and forcing them to stay inside may well turn out to be a death sentence for some of them. The ones who are not yet infected will be forced to remain close to those who are infected but not yet diagnosed. Therefore the spread of the disease within Amoy Garden may continue.
If the disease continues to spread and more quarantines are ordered then it is quite possible that people will resist being quarantined in close quarters with other people who might be infected. The Amoy Garden quarantine is already being enforced by police stationed outside to prevent people from entering or leaving.
The Hong Kong housing block, the Amoy Gardens in Kowloon, was surrounded by about 50 police officers on Monday, as the Hong Kong authorities invoked quarantine laws to try to stem the growing crisis.
In a really large scale outbreak there would not be sufficient numbers of police available to enforce quarantines. If the connection between SARS spread and air ducts is established then in the event of a large scale outbreak many people will likely flee from multi-unit dwellings such as apartment buildings.
While SARS spread on a single floor in the Metropole Hotel the pattern of SARS spread in the Kowloon apartment block is different
"They are finding that the infections are in people living in apartments on top of each other, only in one area of this apartment block. It's only two apartments, but from floor zero to 35. Not all of those apartments are affected, but most of the families affected are living in that small area of that apartment building," virologist Klaus Stohr said at WHO headquarters in Geneva.
One potential explanation for the difference in the pattern of spread in the Metropole Hotel and the Amoy Garden may be a different duct work layout. Ducts might be laid out in a more columnar structure in the Amoy Garden and more in rows in the Metropole.
If, as suspected, SARS is caused by a previously unidentified member of the coronavirus family then it is probably similar to other coronaviruses and possesses the ability to survive on exposed surfaces for a few hours at least. Therefore it might be transmissible by touching a surface at a location where an infected person coughed a few hours previously. Frequent handwashing may help to reduce its spread.
By the end of March 2003 there have been 1622 reported cases of SARS and 58 deaths. That is a nearly 4% death rate. But the actual death rate is likely even higher since some of the currently infected out of the 1622 will eventually die from the infection.
While most types of influenza tend to kill only the very old, the very young, and those who are immuno-compromised SARS kills people in the prime of life.
Dr. Carlo Urbani, an expert on communicable diseases, died today of SARS. Dr. Urbani, worked in public health programs in Cambodia, Laos and Viet Nam. He was based in Hanoi, Viet Nam. Dr. Urbani was 46.
The great influenza pandemic of 1918-1919 (popularly known as the Spanish Flu) also struck down those in the prime of life. Though while Spanish Flu caused the highest mortality rate in those aged 20-39 WHO official Mark Salter says the risks of dying from SARS are greater for those over 40 years old.
Age could be one factor, with people over 40 apparently at greater risk, while the fact that a patient was already suffering from some other chronic ailment, such as heart or liver disease, could also play a part, he said. "The indications seem to be that if the patient is over the age of 40 and has other illnesses as well...they would be more prone to developing a more severe form when the chances of survival become smaller," he told Reuters.
Here are excerpts of the March 29, 2003 CDC press conference held by CDC director Dr. Julia Gerberding. (bold emphases added)
We believe, based on what the investigations have shown us so far, that the major mode of transmission still is through droplet spread when an infected person coughs or sneezes and droplets are spread to a nearby contact. But we are concerned about the possibility of airborne transmission across broader areas and also the possibility that objects that become contaminated in the environment could serve as modes of spread.
Coronaviruses can survive in the environment for up to two or three hours ,and so it's possible that a contaminated object could serve as a vehicle for transfer to someone else.
In health care settings, we have already initiated guidance to protect against droplets, airborne and contact spread of this virus, and today we're issuing an update on how to protect people in homes of SARS patients.
We know that the individual with SARS can be very infectious during the symptomatic phase of the illness. We don't know how long the period of contagion lasts once they recover from the illness and we don't know whether or not they can spread the virus before they have the full-blown form syndrome.
But most of the information that the epidemiologists have been able to put together suggests that the period of contagion may begin with the onset of the very earliest symptoms of a viral infection, so our guidance is based on this assumption.
About one third of all common cold infections are caused by a type of coronavirus. Hence Dr. Gerberding makes a comparison to cold virus spread.
DR. GERBERDING: We are very vigilant about the possibility of spread. We recognize that there are at least some patients with SARS that are extremely efficient transmitters. We don't know to what extent all patients are particularly infectious but there are clearly some who appear to be very highly infectious, and, for example, in Hanoi where there was one patient who was a source for health care worker transmission and approximately 56 percent of the health care who had direct contact with the patient appeared to have acquired SARS.
So given that high degree of contagion and what we know about spread of cold viruses, I think we are very alert to the possibility that this could spread outside of the confined populations that I've mentioned, travelers to the affected areas, close household contacts, and health care workers. But we are not seeing that now and we are looking for it very closely.
So if we begin to appreciate that, we will have to expand our recommendations to be more inclusive of special protective measures for contacts.
The biggest danger is that SARS is spreading in places that are effectively out of sight of Western investigators. The most likely country where SARS is still spreading is China. Western disease experts still have very little visibility into what is really happening with SARS spread in China.
DR. GERBERDING: Well, from the standpoint of CDC, I would say that we are very concerned about the spread of this virus, particularly in Asia. We recognize this as a epidemic that's evolving differently, in different geographies, but nevertheless, it is a respiratory virus, it does appear to be transmitted very efficiently, and what we know about respiratory viruses suggests that the potential for infecting large numbers of people is very great.
So we may be in the very early stages of what could be a much larger problem as we go forward in time. On the other hand, this is new, we don't know everything about it, and we have a lot of questions about the overall spread.
The patterns of transmission in the individual countries vary, depending on where the primary foci of transmission is occurring.
In Hong Kong, the situation is particularly alarming because we have several hospitals that are affected, and there are so many health care workers in each of these hospitals that could have been exposed or who are developing SARS, that there's already a multiplier in the community. Every health care worker has household contacts, those contacts, when they become ill, have had other exposures.
So we are very concerned about the speed and the amplification process in Hong Kong. On the other hand, the health officials there are taking extremely efficient and aggressive steps at this point in time to contain spread in that community, including closing schools and closing hospitals, and cohorting health care workers and patients.
So it remains to be seen whether or not those measures will attenuate the spread. The biggest unknown is of course what is going on in China and we are desperate to learn more about the scope and magnitude of the problem there, because that really I think will be the biggest predictor for where this will be headed over the next few weeks.
Here we are over 5 months after the SARS disease first surfaced in China and CDC and WHO authorities still know little about how the disease developed and spread in China. As a consequence of our ignorance of the disease's spread in China we have only the information developed from the course of its much more recent appearance in Hong Kong and in places outside of China. Therefore we simply do not yet know enough to say what are all the ways by which SARS can be transmitted.
Concerns that I mentioned earlier focused on droplet transmission, so if you were in the elevator and an infectious person literally coughed on you, it's conceivable that you could acquire a respiratory infection, including SARS, through that mechanism.
On the other hand, most of the information suggests that fairly prolonged contact, on a face to face basis, is typical of the transmissions.
There are anecdotal reports, that we haven't confirmed yet, of much briefer contact. There's been a concern expressed about the potential for airborne or surface contamination in the apartment in Hong Kong, and these are all open questions that we are aggressively pursuing here.
It could be worse. A moderately severe influenza strain (i.e. not as bad as the 1918 outbreak but worse than the average influenza strain) has a higher mortality rate than SARS. Though influenza tends to take the very young and very old and hence elicits less fear in the general population.
DR. GERBERDING: Certainly, there could be other cofactors involved such as viruses or underlying illness, but this is just atypical pattern for any infectious disease. If you get pneumococcal infection, many people have completely asymptomatic. Some people get a mild disease and some people have a full blown, very, very severe illness from the infection.
So this is a typical pattern for respiratory illnesses, not something that we're surprised about. In fact if there's any good news in SARS right now, it's that the majority of patients do appear to recover and that the death rate is actually lower than what we see with epidemic influenza, about 3.5 percent of the patients have died from the illness. That is still a tragic occurrence for the people who are affected, and their families, and I would never mean to minimize it. But it is fortunate that it is not even more severe.
The real tragedy in the case of SARS is that the Chinese government has managed to make a bad situation worse. In spite of the fact that SARS first surfaced in China in November 2002 the rest of the world did not hear about it until it started causing infections in Hong Kong and Vietnam a few months later. The irresponsibility of the Chinese government may lead to a massive outbreak throughout the world.
The president of Taiwan, which has 10 cases of Severe Acute Respiratory Syndrome (SARS), has been the most outspoken. "SARS first broke out on the Chinese mainland, but the authorities covered up the information, leading to a global epidemic," Chen Shui-bian said on Friday. China initially admitted to five deaths, but a toll of 31, and 800 infections, since November was revealed on Wednesday.
The press in China is highly controlled and is not a reliable source of information about the extent of SARS in China. Also, the Chinese government has resisted providing the WHO much information about SARS. On Friday March 28 2003, over 5 months after SARS first showed up in China, the Chinese government finally agreed to allow WHO disease experts access to Chinese information about SARS infections in China. But it is far from certain that China will be completely forthcoming. One international health official quoted off-the-record in the article above says that the disease is probably far more widespread in China than the government of China is admitting to even now. There are parts of China that are poor where most of the population have little access to health care services. Even if the most developed countries take steps to slow the spread of SARS at this point it seems likely that SARS will spread in less developed countries.
If China had reported its SARS outbreak back in November of 2002 we'd be about 4 or 5 months further along in developing tests, developing vaccines, studying its mode of transmission, and developing ways to minimize its spread. But the Chinese government instead hushed it up and the result may eventually be millions of deaths that could have been avoided.
What to do to avoid becoming infected? Face masks may not help that much.
Doctors say sick people who put on masks become less likely to transmit the illness when they cough or sneeze. But it is unclear whether the masks help the healthy. They quickly become saturated with moisture from breath and lose some usefulness when worn for hours - much less for days, as is happening here now - local doctors warn.
We really need to know more about the efficacy of facial masks for blocking SARS' spread. If it looks like SARS is going to spread into the general population keep in mind that protecting the eyes from airborne droplets might also be of some value for reducing risks. Goggles or safety glasses might reduce the risks of transmission. Also, frequent hand washing when out in public places may also reduce the risks of getting the illness.
One big question in my mind is about how duct work and air filters are laid out in large buildings. Do most buildings do a good job of filtering out particles from air that comes out of each dwelling or office before that air passes into other areas in the same building? Also, could air filters be rapidly placed into existing buildings to reduce the spread of airborne virus particles? If people begin to fear living and working in large buildings the economic costs of the fear of SARS could become enormous very quickly.
If SARS breaks out into the general population the fatality rate may rise. Currently because so few people have SARS each person can receive a great deal of care including respirators when necessary. But if large numbers of people become infected there will not be enough equipment or medical workers to care for them.
SARS may cause an enormous economic impact. If the fear of SARS grows large enough then many people will avoid both business and personal travel, restaurants, movie theaters, shopping malls, and other public places with large numbers of people. Consumer demand will therefore decline and the rate at which business deals are negotiated will slow.
Also see my previous posts on SARS: Severe Acute Respiratory Syndrome Causing Concerns and Hunt For Cause Of Severe Acute Respiratory Syndrome.
But coronaviruses are prone to transformation. They have an unusually large amount of genetic material, as well as enzymes that enable them to shuffle it. A new, more virulent mutant could easily result.
American Airlines Flight 128 from Tokyo is being held on the tarmac at San Jose International Airport after two passengers and two crew members complained of feeling unwell, airport officials said.
People will become more afraid to fly if SARS continues to spread. Also, if many flights get quarantined there will even be a reduction in the number of flight crews available to fly aircraft.
Some airlines in the Southeast Asian region are moving to reduce the risk of infection. Thai Airways International and other airlines of Thailand are requiring passengers from high risk countries (Singapore, Hong Kong, China, Taiwan and Vietnam) to wear surgical masks.
Here's some more bad news about surgical masks. Australian expert David Bromwich says surgical masks do not provide much protection against airborne disease.
But David Bromwich, an expert in respiratory protection from Brisbane's Griffith University, said that passengers wearing surgical masks to guard against respiratory disease were "kidding themselves". Dr Bromwich said surgical masks were originally designed to stop transmission of saliva from doctor to patient, but offered almost no protection from tiny airborne disease particles. "It's a false sense of security," he said.
Since surgical masks do not provide much benefit I guess it doesn't matter that there is an enormous surgical face mask shortage developing. The 3M plant for manufacturing N95 surgical masks is operating at maximum capacity and can not keep up with demand.
The masks, made of a micro-fibre designed to filter out impurities, are manufactured at a plant in the United States, currently operating 24 hours a day under a "state of emergency."
Canada, which has been much harder hit by SARS than the US faces a surgical mask shortage for medical workers.
Hong Kong just reported a new single day record of 75 new cases of SARS diagnosed and other countries are reporting new cases. These cases are spurring countries in the region most hard hit by this new disease to take increasingly stringent measures to stop the spread of SARS.
Hong Kong invoked a colonial-era law Tuesday to quarantine more than 240 people in countryside vacation camps, part of redoubled efforts to halt the spread of a mysterious flu-like illness that has killed at least 63 people around the world.
The 240 are all from block E of the Amoy Garden apartment building complex.
SARS has so far killed about 3 to 4 per cent of the 1500 sufferers. But be thankful it is not as infectious as common influenza.
"If it were flu, it would be all over the world with millions of people infected," says Victoria's public health chief, Dr Robert Hall.
The containment of SARS has been found to be quite difficult for public health authorities and success is by no means assured. There is a lesson here: If a more easily transmittable disease of equal or greater lethality emerged then unless the threat it posed was recognized at a very early stage and attempts to stop its spread were very aggressive it is unlikely that it could be contained.
|Share |||Randall Parker, 2003 April 01 01:43 AM Dangers Natural Bio|