Plague, most ancient, dreadful and formidable pestilential rodent borne disease was a major public health problem in India till the mid twentieth century A.D. Plague is one of the three epidemic prone diseases still subject to the International Health Regulations and notifiable to the World Health Organization (WHO). In India mortality due to plague reached zero level during 1967. However, sporadic cases of suspected human plague were reported from Himachal Pradesh during 1966 and 1983-1984 and Karnataka during 1984 and at times localized sylvatic plague incidence encountered in the last decade from the trijunction of Karnataka, Andhra Pradesh and Tamil Nadu in peninsular India. During 1994 a bubonic plague outbreak at Beed district, Maharashtra and pneumonic plague outbreak in Surat, Gujarat were recorded. After 8 long years of quiescence a localized outbreak of pneumonic plague occurred in Himachal Pradesh in 2002. In 2004, a bubonic plague outbreak occurred in Uttarkashi district, Uttarakhand.Plague continues to exist as a major public health problem in many countries of the world. In several countries plague has remained quiescent for years together before reappearing all of a sudden. The enzootic foci of plague in India is believed to be present in four groups of foci in northern, central, western and southern India. From 1989 to 1994 active zoonotic foci of plague were detected from the trijunction of Tamil Nadu (Krishnagiri district), Andhra Pradesh (Chittoor district) and Karnataka (Kolar and Bangalore rural district). As the sylvatic rodents live in wild and peri-domestic situations and maintain the natural transmission in enzootic foci for centuries together, eradication of the disease is highly impossible. Natural decline in plague incidence would not justify the conclusion that plague has disappeared from the area. Since the beginning of the 1990s, the number of plague cases shows rising trend worldwide, and outbreaks are reappearing in various countries of the world after decades of quiescence.Under reporting of plague cases may be attributed to lack of diagnostic facilities for the confirmation of the cases and cessation of plague surveillance work by number of erstwhile plague endemic countries, where non-occurrence of cases for long years gave false impression that Yersinia pestis are no longer circulating.A plague outbreak may cause widespread panic, as occurred in India in 1994 when a relatively small outbreak, with 54 deaths, was reported in the city of Surat. Plague should not be relegated to the sidelines. It remains a poorly understood threat that we cannot afford to ignore.Potential new foci should be confirmed and investigated, with special attention to harbours with international trade. National plague surveillance programmes and regional collaboration are needed to be strengthened.
This paper deals with the diffusion approximatien technique for solving piulti-server queueing problems with balking having Erlangian inter-arrival time and Erlangian service time distributions. Probability efjoining of a ' new customer to the system is assumed to vary as e'rv where T is a positive parametef and pt is the queue length. The ap'proximation technique is based on the theery of diffusion, considering only means and variances ofarriyai and 'departure processes, Approximate formultis for P (n), probability of finding n customers in the system, and L, mean number of customers in the system, at steady state, are given. Finally, compaiisons of approximate and exact or si:nulated values of mean number L of customers in the system are made for some EllEk!s (ee) systems with balking to show the effectiveness of the approximation technique and graphs of approximate values of L for several systems are drawn which can be used in practice.
Studies carried out on entomological and rodent surveillance in agroclimatic and feral biotopes of five districts of Maharashtra and two districts of Gujarat revealed that the terrain features of the seven districts surveyed were conducive to wild rodent species, Ta tera indica, a natural reservoir of plague and vector flea species, Xenopsylla cheopis. A total of 214 Tatera indica and three Bandicoota bengalensis were collected from burrows by the digging method and 89 rat fleas were retrieved. The flea index calculated ranged from 0.26 to 1.0 in different districts. The examination of blood serum samples, contact tissue impression smears and tissue organs (heart, lung, liver and spleen) of these wild rodents did not reveal any evidence of plague activity. The natural harbourages of Ta tera indica were found to be elevated land or raised margins of agricultural fields or barren land with thorny bushes/xerophytic plants and parthenium grass. Agricultural fields having wet soil were found to be the preferred harbourages of Bandicoota bengalensis. Movement of wild rodents toward human settlement was observed to be the common phenomenon during the harvesting season which may lead to the creation of favorable conditions for plague outbreaks.
Absttxiet An approximation method based on the diffusion theory is proposed for solving multi-seryer finite queueing preblems haying general independent inter-arrival tirne and general service tirne distributions. The discrete customer flow through the system is approximated by a continuous one, and a diffusion equation for the process of the number of custorners in the system is censtrueted by using means and. variances of the inter-arrival time and service tirne distributions. Two refiecting boundaiies are irnposed at the origin and rn, the maximum number of customers being allowed in the system, Later, the boundary conditions are modified to improve the approximation.Approximate forrnulas for Pn, probability of finding n customers in the system, and for N, mgan number of lost customeis frorn the system per mean service time, are given for steady state, Numerical exarnples for mean nuTnber of customers in the system are presented for some EllEkls(m) systerns to show the effectiveness of the preposed method.
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