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In the present work, a method for computation of vibrational relaxation times based on a kinetic theory definition is utilized to calculate vibrational relaxation times of molecules present in air (N2, O2, and NO) in collisions with air species particles. An overview of available experiment VT relaxation time measurements, as well as quasi-classical trajectory (QCT) calculation results, and various empirical models, is given. Different inelastic cross-section models are used for the computation of the relaxation times, and their parameters are adjusted to fit the available experimental data and QCT results. It is shown that the proposed method of calculation can give a quantitative and qualitative agreement with the available data in a wide range of temperatures; the obtained interaction parameters may be used not only for vibrational relaxation time calculation within a multitemperature framework but also for development of state-specific models for use in CFD and DSMC codes.

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We study coupling of vibrational relaxation and chemical reactions in nonequilibrium viscous multitemperature flows. A general theoretical model is proposed on the basis of the Chapman-Enskog method modified for strongly nonequilibrium reacting flows; the model differs from models commonly used in computational fluid dynamics since it is able to capture additional cross-coupling terms arising in viscous flow due to compressibility and mutual influence of all nonequilibrium processes occurring in a mixture. The set of fluid dynamic equations is derived starting from the Boltzmann equation; the relaxation terms in these equations are described using the kinetic transport theory formalism. Reaction and relaxation rates depend on the distribution function and thus differ in the zero-order and first-order approximations of the Chapman-Enskog method. An algorithm for the calculation of multitemperature reaction and relaxation rates in both inviscid and viscous flows is proposed for the harmonic oscillator model. This algorithm is applied to estimate the mutual effect of vibrational relaxation and dissociation in binary mixtures of N(2) and N, and O(2) and O, under various nonequilibrium conditions. It is shown that modification of the Landau-Teller expression for the VT relaxation term works rather well in nitrogen, whereas it fails to predict correctly the relaxation rate in oxygen at high temperatures. In oxygen (in contrast to nitrogen), the first-order cross effects of dissociation and VT relaxation are found to be significant. A method for calculation of vibrational relaxation time based on the kinetic theory definition is suggested. Two-temperature dissociation rate coefficients are calculated in the zero- and first-order approximations and compared to other models.

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After >10 years without detection of any cases of wild virus-associated poliomyelitis, a large outbreak of poliomyelitis occurred in Albania in 1996. A total of 138 paralytic cases occurred, of which 16 (12%) were fatal. The outbreak was due to wild poliovirus type 1, isolated from 69 cases. An attack rate of 10 per 100,000 population was observed among adults aged 19-25 years who were born during a time of declining wild poliovirus circulation and had been vaccinated with two doses of monovalent oral poliovirus vaccines (OPVs) that may have been exposed to ambient temperatures for prolonged periods. Control of the epidemic was achieved by two rounds of mass vaccination with trivalent oral poliovirus vaccine targeted to persons aged 0-50 years. This outbreak underscores the ongoing threat of importation of wild poliovirus into European countries, the importance of delivering potent vaccine through an adequate cold chain, and the effectiveness of national OPV mass vaccination campaigns for outbreak control.

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UNLABELLED: Indigenous wild polioviruses have been virtually eliminated from the 51 countries of the European Region of the World Health Organization (WHO), an achievement that is of critical importance to the global initiative to eradicate poliomyelitis by the year 2000. An international commission has been established to certify the elimination of poliomyelitis from this region. European countries have recently been requested to establish National Certification Committees to review and submit the necessary documentation and surveillance data. In some Western European countries where polio has not been reported for many years, the challenge will be to produce robust evidence demonstrating both the current absence of wild poliovirus and the means to promptly detect and respond to possible importations of wild poliovirus for the next several years, up to global eradication and the cessation of polio vaccination. KEY MESSAGES: 1. laboratory-based surveillance with collection of faecal specimens is necessary to demonstrate the absence of indigenous wild poliovirus 2. certification can only occur after all countries have demonstrated the absence of indigenous wild polioviruses for at least 3 years and have the means to detect and respond to importations of wild poliovirus for several years into the future 3. any single case of poliomyelitis in Europe now requires an immediate public health response which includes virological investigation and prompt notification to the World Health Organization.

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Ten years after the year 2000 target was set by the World Health Assembly, the global poliomyelitis eradication effort has made significant progress towards that goal. The success of the initiative is built on political commitment within the endemic countries. A partnership of international organizations and donor countries works to support the work of the countries. Interagency coordinating committees are used to ensure that all country needs are met and to avoid duplication of donor effort. Private sector support has greatly expanded the resources available at both the national and international level. At the programmatic level, rapid implementation of surveillance is the key to success, but the difficulty of building effective surveillance programmes is often underestimated. Mass immunization campaigns must be carefully planned with resources mobilized well in advance. Programme strategies should be simple, clear and concise. While improvements in strategy and technology should be continuously sought, changes should be introduced only after careful consideration. Careful consideration should be given in the planning phases of a disease control initiative on how the initiative can be used to support other health initiatives.

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In 1988, the World Health Assembly set a target of global eradication of poliomyelitis due to wild poliovirus by the year 2000. The strategies of the campaign are: reach and maintain high levels of routine vaccination coverage throughout the population; p

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In the European Region of the World Health Organization, all countries in which polio is endemic have adopted the following strategies: achievement of high routine vaccination coverage, implementation of supplemental immunization activities, and enhancement of surveillance for poliomyelitis. In 1995, 205 cases of poliomyelitis were reported. Routine coverage among 1-year-olds with three doses of poliovirus vaccine was 89% in 1995. Ten countries conducted national immunization days (NIDs). Twenty-four countries (48%) adopted acute flaccid paralysis (AFP) surveillance. Use of NIDs has decreased poliomyelitis incidence in the seven countries in which polio is endemic (Armenia, Azerbaijan, Kazakhstan, Turkey, Turkmenistan, Tajikistan, Uzbekistan) from 203 cases in 1994 to 47 in 1995, a 77% reduction. Full implementation of the strategies to achieve eradication in the countries in which polio is endemic, including those countries with epidemic poliovirus transmission during 1995, is likely to accomplish regional eradication of poliomyelitis by the year 2000 or earlier.

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Oral poliovirus vaccine (OPV) was not available in Samarkand, Uzbekistan, from November 1992 to August 1993. The ensuing outbreak of poliomyelitis was investigated: Patients with poliomyelitis were evaluated, the extent of poliovirus circulation was estimated, and the effectiveness of control measures was assessed. Between March 1993 and April 1994, 74 cases of paralytic disease attributable to poliovirus type 3 were reported. Cases originated from 63% of districts; 88% of cases were children < or = 2 years old, and the highest attack rates were for infants 9-11 months (65/100,000) and 12-14 months (60/100,000). Most patients were either unvaccinated (45%) or inadequately vaccinated (23%). Limited quantities of OPV became available in September 1993 and were provided to infants (3 doses) and 1-year-olds (2 doses), controlling rapidly the outbreak in these age groups, but cases continued, primarily among older children, until April 1994. These findings suggest that control efforts should be guided by the age distribution of the children with poliomyelitis.

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Following the introduction of routine immunization with diphtheria toxoid in the 1940s and 1950s, diphtheria incidence declined dramatically in countries of the industrialized world. At the beginning of the 1980s many of these countries were progressing toward elimination of the disease. However, since the mid-1980s there has been a striking resurgence of diphtheria in several countries of Eastern Europe. For 1993, WHO received reports of 15,211 diphtheria cases in Russia and 2,987 cases in Ukraine. The main reasons for the return of diphtheria in these countries were: decreasing immunization coverage among infants and children waning immunity to diphtheria in adults, movements of the population during the last few years, and an irregular supply of vaccines. The outbreak spread to neighboring countries and in 1993 cases were reported in Azerbaijan, Belarus, Estonia, Finland, Kazakhstan, Latvia, Lithuania, Poland, Tajikistan, Turkey, and Uzbekistan. Epidemiological patterns of diphtheria are changing in developing countries, and the disease seems to be following patterns seen in industrialized countries 30 to 40 years ago. In developing countries, routine immunization against diphtheria was introduced in the late 1970s with the Expanded Programme on Immunization. In these countries, coverage of infants with 3 doses of diphtheria toxoid reached 46% in 1985, and 79% in 1992. Recent diphtheria outbreaks in Algeria, China, Ecuator, Jordan, Lesotho and Sudan demonstrate a shift in the age distribution of cases to older children and adults. Rapid clinical and public health responses are required to control diphtheria outbreaks. Three major measures are indicated: high immunization coverage of target groups, prompt diagnosis and management of diphtheria cases, and rapid identification of close contacts with their effective management to prevent secondary cases.

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The European Region is passing through a period of rapid transition with the most dramatic changes in the CCEE and NIS. The provision of adequate vaccine supplies has become a priority for many Member States in their efforts to sustain immunization activities. The Regional Office has therefore launched a special programme on vaccines for CCEE/NIS. New operational targets for the Expanded Programme on Immunization (EPI) in Europe in the 1990s were established by the European Advisory Group in 1993. These operational targets highlight the steps countries need to follow to achieve the European target 5. Immunization coverage generally remains high and stable in the Region. In 1990-1992 pockets of non-immunized individuals in different countries led to out-breaks of disease. Currently, the low coverage with DPT(DT vaccines in many provinces of the Russian Federation is one of the reasons for the epidemic of diphtheria that has affected the country since 1990. Despite the difficulties experienced by many CCEE and NIS, progress has been observed. Morbidity from poliomyelitis declined during 1990-1993. There remain only a few hot spots with endemic transmission of wild poliovirus: the Balkans, trans-Caucasus and central Asia. The diphtheria situation deteriorated in 1990, becoming increasingly dramatic in 1992 and 1993. Almost all cases have been reported from the Russian Federation and the Ukraine. Increasing diphtheria morbidity has been observed in Belarus, Kazakhstan and Uzbekistan.

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The WHO Regional Office for Europe is committed to the eradication of poliomyelitis in Europe, as a part of the WHO effort to achieve the world eradication of polio by the year 2000. The European Advisory Group on EPI has adapted in 1993 the operational targets for the regional eradication of polio, which focus on surveillance, outbreak response, and immunization coverage. Policies recommended by WHO have been translated into plans for action by 9 European countries among those which still reported cases of polio. The Regional Office for Europe of WHO has concentrated its efforts in the following areas: 1. Implementation of essential strategies on immunization (mopping-up or national immunization days) in countries having high-risk areas with endemic transmission of wild poliovirus. 2. Improvement of surveillance, which is a major strategic component. Its key element is the surveillance of acute flaccid paralysis. Its implementation started in Europe in 1991. 3. Development of a regional laboratory network involved in the routine diagnosis of poliomyelitis. The network began to be operational in 1991. In 1992 polio morbidity, reported by 17 countries, has shown a downward trend as compared to 1991. Anyhow, some foci of wild poliovirus activity still persist in the Balkan countries, the Trans-Caucasian region, and several Central Asia republics of the former Soviet Union. The main limitations to progress in polio eradication in Europe are: absence of strong political support at the national level; lack of financial support, which may delay the translation of WHO recommendations into proper action at the national level; availability of polio vaccine, which may become a problem in the absence of adequate support; and the unsatisfactory pace of improvement of the polio surveillance.

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The epidemiological analysis of an outbreak of salmonellosis, registered in May 1988 on the territory of two regions of the Karelian ASSR and covering 10 villages, was carried out. Altogether 112 persons were affected. One-day old chickens sold to the population by the local poultry plant were the source of infection which was transmitted through everyday contacts: those persons who had direct contact with chickens were affected. S. enteritidis with similar biological characteristics were isolated from salmonellosis patients, from persons having had contacts with chickens and from chickens. Chickens were probably infected by oral route.

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