Generality
Also known as acute respiratory syndrome, SARS is a potentially lethal contagious viral disease. It mainly affects the respiratory system, causing atypical pneumonia and a number of other symptoms very similar to those of influenza.
The first (and only, currently) SARS epidemic occurred between 2002 and 2003, in China. From there, the virus spread rapidly in many other Asian countries and beyond. The discovery of SARS is due to an Italian doctor, Carlo Urbani, who was one of the 775 victims of the epidemic infection.
Currently, there is still no effective cure or even a vaccine. However, microbiologists are studying the virus to find its weak point.
What is SARS?
SARS, also called acute respiratory syndrome, is a highly contagious form of viral pneumonia, which seriously endangers those who contract it.
HISTORY OF SARS
SARS first appeared in November 2002, in China, in Guandong province. From that moment on, in a few months, it spread to another 30 countries, mostly Asians (Hong Kong, Singapore, Taiwan, Vietnam, etc.), but also, albeit with very few cases, in Canada, the United States and Europe. This rapid spread to different parts of the globe was due to air travel by sick people.
Between November 2002 and July 2003, the SARS caused, in the Asian reasons concerned, a real epidemic: it infected more than 8, 000 people and caused the death of 775. Then, thanks to the appropriate health countermeasures and quarantine, it was possible to stop its propagation.
In western countries, instead, always in the same period of time, the cases (or suspected such) of contagion were very few and promptly placed in isolation. In Canada, in Toronto, just over 200 cases occurred; across Europe, not even a dozen.
The identification of SARS is due to an Italian doctor, Carlo Urbani . He, before dying of the effects of this infection (March 2003), communicated his important discoveries to the WHO (World Health Organization), in late February 2002. It was thus that the global alert set off.
It has been 10 years now that SARS cases in the world no longer occur.
Countries where SARS presented itself with more than one case:
- China; Hong Kong; Taiwan; Canada; Singapore; Vietnam; United States; Philippines; Mongolia; South Korea
Figure: The places in the world where SARS has spread . From //en.wikipedia.org
Epidemiology
There is considerable uncertainty about the lethality rate that characterizes SARS. According to the World Health Organization, lethality is estimated at between 14 and 15%; according to other sources, it is inferior.
It must then be added that this datum is an average value; for example, the statistics show that most deaths have affected people aged 65 and over (lethality value 50%), while in patients gradually younger the lethality was progressively lower (about 1% for patients maximum 24 years).
NB: lethality is the ratio between the number of deaths, for a given disease, and the number of individuals suffering from the same disease.
Causes
The cause of SARS is a virus belonging to the family of coronaviruses, called SARS-CoV . To this same family, some well-known viruses belong to us (especially in the colder seasons), which cause the classic colds .
I CORONAVIRUS AND THE ORIGIN OF SARS Co-V
Figure: the SARS coronavirus. From //it.wikipedia.org
Carnivorous animals, from which SARS seems to originate:
- Raccoon dog
- Ferret badger (Melogale)
- Palm Owl (Paguma larvata)
- Domestic cats
Coronaviruses are single-stranded RNA viruses, which generally cause enteric infections (ie at the level of the intestine) and / or pathway areas (ie at the level of the lungs).
Until SARS appeared, the only coronaviruses known to cause lethal effects on the infected organism were animal coronaviruses. This led us to think, then, that the human SARS virus derived from a virus of animal origin, which, following a mutation, would have adapted to the human species ( zoonoses ).
The animals initially found to have given rise to the human SARS virus were wild carnivores and domestic cats. Subsequently, some researchers discovered that there were notable analogies between the human SARS virus and that of the bats in Southeast Asia. In light of this latest discovery, the investigations became more detailed and, a few years later, the hypothesis was born that bats were the healthy carriers of the disease, the so-called virus reservoir.
However, even today, these studies present outstanding points and deserve further study.
What is a zoonosis?
The term zoonosis refers to any infectious disease that can be transmitted from animals to humans. Very often, these diseases do not cause particular problems, except in the person who contracts them. However, in some cases, it can happen that the infectious agent (virus or bacterium), which triggers them, changes and adapts to the human species. In such situations, the disease can take on epidemic characteristics.
Typical examples of zoonoses are bubonic plague, Lyme disease, salmonella and West Nile fever .
HOW IS THE VIRUS TRANSMITTED?
Like other coronaviruses and like influenza viruses, SARS-CoV also spreads through volatile droplets of saliva, expelled by an infected individual when he speaks, sneezes, coughs or, although rare, breathes.
However, it was found that there are other indirect transmission methods. It is possible, in fact, that the virus spreads through contact with contaminated objects or environments: for example, touching buttons, telephones, handles, toilets etc., recently used by a SARS patient, can determine the onset of the infection. The same applies to the sharing of crockery and cutlery.
WHO IS A HIGHER RISK OF CONTAGUE?
SARS transmission method :
direct:
- Volatile droplets due to sneezing, coughing, breathing
indirect:
- Contact with contaminated objects (telephones, buttons, etc.)
- Contact with a patient's organic fluids (faeces)
Given the way in which it is transmitted, the SARS virus spreads more easily when a person is in close contact with an infected person. By close contact, we mean the so-called face-to-face relationship, which in medical-epidemiological terms means less than a meter away. Not surprisingly, at the beginning of the epidemic, the first people to fall ill were those who cared for the sick, such as family members or doctors.
The airborne transmission of the virus, on the other hand, has never been demonstrated (by air transmission we mean the infection between individuals placed at a distance greater than one meter).
Symptoms and Complications
The first symptoms of SARS resemble those of a common flu . Therefore, the patient manifests:
- High fever, above 38 ° C
- Fatigue sensation
- Headache
- Sore throat
- Chills of cold
- Musculoskeletal pains
- Loss of appetite
- Diarrhea
- He retched
COMPLICATIONS
After 3-7 days from the onset of the first symptoms, the infection worsens and the most dramatic complications of SARS arise, which can lead to the death of the patient. This is the moment in which gastrointestinal disorders, muscular pains are accentuated and the first signs of pneumonia appear, namely dry cough and breathing difficulties .
Death occurs due to severe respiratory failure .
Possible other complications include heart failure and kidney failure .
FOR WHAT PATIENTS IS FATAL?
SARS-CoV can indiscriminately infect anyone. However, there are more predisposed subjects than others. As mentioned above, the highest lethality rates were recorded among the elderly (aged 60-65). This is explained by the fact that these individuals generally have a weaker immune system (ie the protective barrier of an organism, against infections and diseases) than an adult in full health.
Other favorable circumstances are linked to the general state of health of an individual: it has been seen, for example, that those suffering from diabetes or hepatitis were more easily infectious.
INCUBATION TIMES
The incubation period, or the time frame between direct contact with a sick person and the appearance of the first symptoms, ranges from 2 to 10 days. However, in some rare cases, it can last up to 14 days.
WHEN DOES A SICK TRANSMIT SARS?
A healthy individual is at high risk of infection if he has a relationship with a SARS patient whose symptoms have appeared for up to 10 days. In other words, during incubation and the first 10 days after the onset of fever, the chances of a patient transmitting the infection are reduced.
Diagnosis
When the SARS epidemic was underway, the following was established to establish the correct diagnosis:
- The presence or absence of the classic SARS symptom, high fever, was evaluated.
- It was investigated whether the patient had contact with affected people or had traveled to regions considered by the WHO to be at risk of infection (endemic areas).
- A stethoscopic examination of the lungs was performed, if the patient complained of the symptoms for at least 3-7 days.
If the possibility of a SARS infection was more than concrete, we proceeded with X-ray examinations of the chest and with laboratory investigations .
At present, these diagnostic procedures still appear to be the most appropriate.
STETHOSCOPIC EXAMINATION
The stethoscopic examination of the lungs can detect abnormal sounds, similar to rales, at the time of the respiratory act. This usually occurs 3-7 days after the onset of fever, ie when the infection begins to get worse.
RADIOLOGICAL EXAMINATION OF THE CHEST
Figure: a chest x-ray of a patient with SARS. From //it.wikipedia.org
X-ray examination of the chest, in patients with SARS, may show signs of atypical pneumonia or respiratory distress syndrome . However, in some cases, the exam may be negative.
NB: Pneumonia caused by bacteria and viruses, which are usually not associated with this disease, are defined as atypical.
LABORATORY EXAMINATIONS
Parallel to chest radiography, laboratory tests should also be performed, known as ELISA, immunofluorescence and PCR ; these investigations serve to identify, in a sample of tissue or blood of the patient, the possible presence of SARS-CoV.
The WHO, at the time of the epidemic, called the diagnoses, carried out with these procedures, as "SARS confirmed in the laboratory", in support of their reliability.
Treatment
There is still no specific therapy for SARS today.
As soon as it was ascertained that it was a viral disease, antibiotics were no longer taken, quite rightly, into consideration. Antiviral drugs (ribavirin) and steroids were tried, but without satisfactory results.
Therefore, the only pharmacological countermeasures considered appropriate were the antipyretics, to reduce, at least, the flu-like symptoms.
Alongside the pharmacological aspect, it is appropriate to recall the essential nature of assisted breathing, guaranteed by hospital equipment. In fact, the patient with SARS needs oxygen, as his respiratory capacity is severely reduced.
HOW TO ACT IN EMERGENCIES?
Based on the experience of 2002-2003, and the well-known characteristics of the virus, a patient with SARS requires:
- Hospitalization
- Insulation in so - called negative pressure chambers (quarantine)
- Assisted ventilation (or breathing)
- antipyretics
VACCINE AND RESEARCH
Unfortunately, there is still no anti-SARS vaccine . Microbiological researchers are studying the virus in every component, to identify a weak point and create a suitable vaccine countermeasure.
Numerous studies are also underway, aimed at identifying effective antiviral drugs. Even in this field of research, it is essential to know the virus responsible for the infection thoroughly.
Prognosis and prevention
The prognosis, for a SARS patient, depends on some characteristics of the patient, such as age and general health status. In fact, as has already been said, the virus made many victims among those over 60 and those who were not in full health, while it had a much less lethal effect among healthy adults.
THE CONSEQUENCES OF THE EPIDEMIA
Some individuals, suffering from SARS and then recovered, have developed, several years later, various disorders, such as osteoporosis, avascular necrosis and pulmonary fibrosis . These pathologies are not only linked to the complications of viral infection (pulmonary fibrosis), but also to therapeutic treatments, to which a patient has been subjected (osteoporosis and avascular necrosis). For example, in the case of avascular necrosis, it can be caused by prolonged use of steroid drugs.
PREVENTION
The preventive measures, useful to avoid the spread of SARS, consist of:
- Quarantine the patient or affected patients.
- Avoid, as much as possible, direct contact (less than a meter) with SARS patients (this advice is to be followed especially in the 10 days following the appearance of the first symptoms).
- Wash your hands with alcohol-based cleaners .
- Use gloves, glasses and cover your mouth and nose with a mask (if you are seeing a patient); cover your mouth and nose with your hand when you sneeze or cough (if you are the sick person).
- Avoid sharing food and everyday utensils with affected people.
- Regularly disinfect the surfaces of the rooms where a patient with SARS lives.
