Legionnaires disease

Contamination of indoor air in living and business quarters is considered the principal source of hazard for human health. There is a direct connection between the quality of indoor air and the number of disease instances. According to the data gathered by researchers over many years, indoor air in living quarters and offices is 4-6 times more polluted and 8-10 times more toxic than outdoor air.

It contains both natural allergens and chemical agents (tobacco smoke and other hazardous organic and inorganic substances). The implications of this fact are the more grave, because people living in cities spend on the average 80% of their life span indoors.

No wonder, therefore that climate control systems are an essential part of the modern lifestyle. Air conditioners can find their place soon in each Moscow apartment, next to a video-recorder or a computer.

However, water used in the cooling systems of the air conditioners, circulating water supply systems of the refrigerating machine condensers, adiabatic sprayer, disk, and checker chambers and heated trays for air moisturising contains various bacteria, mineral suspended particles, fibres, corrosion products, and often also pathogenic microorganisms. This water often becomes the source of dangerous diseases.

More than a quarter of a century has passed since the first Legionnaires disease instance. Legionellosis is a dangerous form of acute pneumonia caused by Legionella pneumophila bacteria. The first instance of this disease was recorded in Philadelphia among the participants of the American legion congress, thence its name. Thirty-four of 240 infected died during that epidemic.

Legionnaires disease (legionellosis) is one of the most dangerous infectious diseases. It was however unknown before 1970s. It leads as a rule to a heavy form of pneumonia and thus to a lethal outcome in 20-25% of the cases. Most of the antimicrobial medicines have low efficiency against this disease.

The pathogens of this dangerous disease with high rate of lethal outcomes are legionellas, bacteria that can be found among the microbial flora in many natural and artificial pools. These bacteria propagate effectively in warm water. In nature legionellas inhabit freshwater pools and are the symbionts of green-blue algae, and also parasitise water and soil amoebas, infusoria, and other protozoa.

The most serious instances of legionellosis:

1985, Stafford (United Kingdom): 68 infected, 23 died.

1987, Victoria State (Australia): 10 deceased.

1999, Netherlands. The number of lethal outcomes, according to the official report, was 31. However, the real number was much greater, because doctors tended to see the cause of rapid increase of lethal outcomes of their patients in ordinary pneumonia. Decorative bubbling pool at a flower exhibition was proven to be the source of pathogens.

2000, Melbourne (Australia): more than 90 infected, 3 died.

2001, Spain: 650 infected, 2 deceased. The source of pathogens could not be found.

Legionellas also penetrated the cooling systems (including power plant cooling towers), compressors, shower cabins, Jacuzzi, and respiratory therapy equipment. Microbes inhabit synthetic and rubber surfaces of water pipelines, and of industrial and medical equipment.

These bacteria are transferred with minute water droplets. Water in air conditioning systems provides the ideal conditions for these bacteria. Therefore the disease caused by Legionellas occurs most often among people spending a lot of time in places equipped with such climate control systems (hotel staff and guests, patients and staff in medical institutions, as well as people working in air-conditioned offices and industrial facilities).

British researchers found legionellas in 42% of the hotels, 70% of medical institutions and offices, and 40% of living quarters. The most favourable conditions for legionella propagation can be found in textile factories where fibres getting into moisturising devices provide the feeding medium for the bacteria.

Epidemic instances of this disease occurred in many countries of Europe, America, Asia, and in Australia. The first legionellosis instances were recorded in Russia in 1980.

Legionellosis epidemics occur in crowded places and during social events. Elderly people, as well as those with immune system deficiencies are the most susceptible to this disease. However, since legionellas often inhabit large-scale climate control systems, the contagion risk is rather high for everybody who works in air-conditioned offices, visits theatres and hotels.

The problem is that water can not be completely purified from legionellas. Therefore the most practicable way to ensure the quality of water in air conditioning systems is to limit the bacteria propagation (within the limit of 10000 per litre). Various technologies are used for this purpose, including application of antimicrobial chemicals.

The studies of these recently discovered bacteria in Russia are co-ordinated by S.V.Prozorovsky, member of the Russian Academy of Medical Science. Under his guidance the researchers of the N.FGamalei Research Institute for Microbiology and Virology developed efficient techniques for diagnostics of this disease, studied the pathogens and their proteins.

Research performed by the Institute of Ecotechnologies in co-operation with the Gamalei Institute for Microbiology and Virology has shown that Phosphopag has a high antimicrobial activity against various strains of legionellas. Application of Phosphopag leads first to the suppression of life activity of the bacterial population in water, and then to their death within 0.5-3 hours.

Konstantin EFIMOV

Director of the Institute

of Ecotechnologies

Sergey MARTYNENKO

Thirteen people were infected with fowl plague through the contact with domestic fowl in Vietnam and Thailand, 8 of them died. There are no scientifically proven possibilities of fowl plague direct transfer man-to-man. However, people can be infected through the contact with the infected fowl during slaughtering and transport.

The researchers suspect that this dangerous infection can be transferred via swine, which are susceptible to the human and fowl type of grippe both. Apart from the strains common in Asia, a new type of fowl plague pathogen was found in the USA. Food and Agriculture Organisation of the United Nations, International Epizootic Bureau, and the World Health Organisation issued a joint statement concerning the world-wide prevention of fowl plague propagation.

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