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What are Corona virus-Type of diagnosis-Therapy specific-Possibility of a vaccine-Avoid useless alarm
By Prof. Antonino Aceti and Dr Simone Lanini of La Sapienza University in Rome
Rome (Fides Service) – An analysis confirms that there is no risk of contracting the virus through contact with objects of food imported from countries with an epidemic and the economies of countries mainly affected can draw a sigh of relief.
A study which appeared recently on one of the most prestigious international medical reviews on 138 patients with SARS suspected or probable hospitalised only 32, that is 23%, were moved to intensive care units, 19 (13.8%) needed respiratory assistance and among these 5 (3.6%) died, all suffering from some chronic disease.
The World Health Organisation, WHO confirmed on 5 June 8,403 cases of SARS with 755 deaths (9.8%); this information can be compared with an epidemic of influenza which last year in the United States alone caused 35,000 deaths and that of acquired pneumonia in communities which has a lethal effect of 4.9%.
Although some perplexity remains, it would seen that the agent responsible for this disease is a new virus which is presently classified as unique belonging to the 4th group of the family of Corona-virus to which has been given the same of SARS –CoV (C0= corona, V=virus).
Corona virus is all “RNA-virus non segment of a single filament with positive polarity”. This means these viruses have an intrinsic and special capacity to change and this allows them to adapt swiftly to an environment and therefore to resist the defences of the organism they infect.
At present diagnosis of SARS is only by exclusion; in fact as things stand each case according to clinical and epidemiological parameters must be classified as probable, suspect or discarded/
Moreover according the indications given by the CDC centre of Disease Control) and the WH, none of the laboratory tests to identify the etiological agent can be considered diagnostic and this is explainable for at least 2 reasons. First of all tests have not yet been standardised and secondly the positive demonstration for a test which identifies SARS Co-V is the demonstration of an infection which has happened and which does not coincide at all with the sickness. All tests) research for anti-bodies, molecule identification, isolation of the virus in cell cultures) are at the moment to be considered as being evaluated.
At the moment there is no special therapy for this pathology; in the most serious cases it is possible to give support treatment to help the patients overcome the acuteness of the symptomatic picture. Patients with ipossia should be admitted to intensive care unites if the oxygenation of the arteries is inferior to 80mmHg and, in the case of signs of respiratory insufficiency, treated with assisted breathing. Treatment of all patients in intensive care could include the giving oxygen with nasal tubes, steroid by mouth to modulate the inflammatory response, ribavirina (which is an a-specific anti-viral to try to stop the diffusion of the virus in the organism and broad antibiotic treatment to avoid the possibility of bacterial super-infection. It must however be underlined that with the sole exception of respiratory assistance there is no consensus for giving other treatment and aneddotic cases indicate that they are of no use.
We come now to speak of the so-called antiSARS vaccine. If for vaccine we mean an active immunising prophilasses, or treatment given to healthy people to render them immune to the infection for a given period of time, certainly the path be taken is long for at least two reasons. In the first place to produce a vaccine it is necessary to be certain about the etiological agent and to know approximately well its biological structure. At present SARS-CoV is only probably the etiological of SARS but some authors indicate as provoking or associated factors also other virus such as the Metapneumovirus (especially in the Canadians isolated) a virus which differs from the Corona virus which seems to have some characters of likeness to the synsiziale respiratory virus which causes serious disease in infants; on the other hand the genome of the virus and its biological structure have only been recently identified.
Secondly, of great importance, the element of security. In fact every new vaccine produced, before being effective must be harmless because as we said above, it is to be given to healthy persons.
However research has started. In fact three US government agencies for health care research, the MIH National Institute of Health, the DHHS (Department of Health and Human Service) and NIAID National Institute of Allergy and Infectious Disease, promulgated on 22 April a joint competition to involve in research all privates whole already from 10 April Aventis-Pasteur company (world leader in vaccine production) at the direct request of the US government began to collaborate with the research. Obviously there are only a few rumours with regard to progress in research; it would seem nevertheless that experimentation in vitro is about to conclude and that before long testing on animals will start, in fact some sources say the vaccine will be available in a record time of only three years.
By way of conclusion we must avoid pointless alarm above all in countries like Italy in which the epidemic did not develop. If on the one hand there is concern about the inter-human transmission from infected person to healthy person via air, at least two elements must be explained: in the first place SARS is an acute disease which means there can be no healthy carriers for a prolonged period of time as for the HIV, this means that a person with SARS is therefore “infected” and is easily recognised; in the second place contact with an infected person who can transmit the disease must be, as indicated by WHO and the CDC, “close” namely an embrace, a kiss, or prolonged conversation at a distance of less than 1 meter. Moreover there is no risk of infection through contact with objects or food imported from countries with a SARS epidemic. This means we can consider certainly not infected people of many ethnic groups coming from countries “at risk” before the outbreak of the epidemic or healthy people returning to Italy or even those who are sick with clinica compatible with suspect infection when symptoms of the disease appeared more than 16 days after their return. Totally unfounded is the fear of contracting the infection by going to ethnic places, for example Chinese restaurants, since the possibility of transmission of the infection through goods or food has never been proved.
Lastly, a consideration dictated by reasonability. The planet has always been and will be travelled by infective epidemics more or less serious and the present SARS epidemic is neither the most serious nor the most concerning and the common efforts at the international level are already having excellent results and in fact WHO announced on 9 June a decline in new cases and deaths also in Hong Kong and Taiwan and this is in agreement also with certain biological characteristics of viruses which, being compulsory endocellular parasites with no expectation of life outside their host the tend by nature to disappear. To better understand this final concept it is enough to return to the beginning of the last century when the distemper virus was introduced in Australia. The virus can infect wild rabbits and reduce the number of these animals which, arrived with settlers and had increased causing serious damage to agriculture. In fact in the first year many rabbits were infected and died and their number dropped considerably. Nevertheless already at the beginning of the second year the number of rabbits present started tog row again although the virus was still in the environment. This happened because during the epidemic increasing weaker viral stocks were selected and these circulated better than virulent stocks because of their capacity to produce a less serious disease in the infected animal, which lived better and longer and was better able to transmit the infection. In agreement with the observation made we can see that also in the present SARS epidemic, the epidemic breeding grounds which still produce deaths are those closest to the areas in which the disease emerged (Hong Kong, Taiwan) or where presumably there still persist viral stocks less changed compared to the virus which at the beginning infected the first case from which the epidemic began. AP (Fides Service 11/6/2003 EM lines 103 Words: 1414)
