The progress of the Polio Eradication Initiative: what prospects for eradicating measles?
Although various attempts have been made to eradicate infectious diseases, only smallpox has been eradicated to date. Polio is targeted for eradication in 2000 and already planning has begun for the eradication of measles. However, before we commit to a measles eradication effort, we must examine the lessons to be learned from polio eradication. Of particular importance is the debate over whether resources should be invested in 'horizontal' or 'vertical' programmes. The outcome of these debates will have a very deep and lasting impact on global health development in years to come. Collaboration between targeted programmes and the primary health care sector through polio and measles eradication efforts will help bring about the necessary balance between goal-oriented programmes, which are subject to quality control and can be evaluated by measurable outcomes, and broader efforts to build up sustainable health infrastructure. (+info)
A variant of variola virus, characterized by changes in polypeptide and endonuclease profiles.
A variant of variola virus is described which produces a late polypeptide of 25 kDa instead of one of 27 kDa and which has an additional endonuclease cleavage site for SalI in the viral DNA. These markers were shown to be genetically independent and to characterize 14 of the 48 variola strains which were examined. The variant strains were isolated from smallpox outbreaks originating in or from Pakistan between 1961 and 1974 and also from two cases at a Mission Hospital in Vellore, India in 1964. No variant strains were found among 9 other isolates from cases of variola major occurring in other parts of India or in Bangladesh, nor among 4 isolates from Indonesia, 15 from Africa or 6 isolates of variola minor. (+info)
Cidofovir protects mice against lethal aerosol or intranasal cowpox virus challenge.
The efficacy of cidofovir for treatment of cowpox virus infection in BALB/c mice was investigated in an effort to evaluate new therapies for virulent orthopoxvirus infections of the respiratory tract in a small animal model. Exposure to 2(-5)x10(6) pfu of cowpox virus by aerosol or intranasally (inl) was lethal in 3- to 7-week-old animals. One inoculation of 100 mg/kg cidofovir on day 0, 2, or 4, with respect to aerosol infection, resulted in 90%-100% survival. Treatment on day 0 reduced peak pulmonary virus titers 10- to 100-fold, reduced the severity of viral pneumonitis, and prevented pulmonary hemorrhage. The same dose on day -6 to 2 protected 80%-100% of inl infected mice, whereas 1 inoculation on day -16 to -8 or day 3 to 6 was partially protective. Cidofovir delayed but did not prevent the death of inl infected mice with severe combined immunodeficiency. Treatment at the time of tail scarification with vaccinia virus did not block vaccination efficacy. (+info)
Smallpox and its control in Canada.
Edward Jenner's first treatise in 1798 described how he used cowpox material to provide immunity to the related smallpox virus. He sent this treatise and some cowpox material to his classmate John Clinch in Trinity, Nfld., who gave the first smallpox vaccinations in North America. Dissemination of the new technique, despite violent criticism, was rapid throughout Europe and the United States. Within a few years of its discovery, vaccination was instrumental in controlling smallpox epidemics among aboriginal people at remote trading posts of the Hudson's Bay Company. Arm-to-arm transfer at 8-day intervals was common through most of the 19th century. Vaccination and quarantine eliminated endemic smallpox throughout Canada by 1946. The last case, in Toronto in 1962, came from Brazil. (+info)
Experimental study of the role of inactivated vaccine in two-step vaccination against smallpox.
In experiments on rabbits it was found that although administration of inactivated smallpox vaccine did not induce a demonstrable antibody response in the serum it enhanced the immune response to subsequent inoculation with live vaccine. The dose of inactivated vaccine corresponded to 8 x 10(7) PFU before inactivation (by (60)Co gamma-radiation); the dose of live vaccine was 1.2 x 10(5) PFU. When the interval between the two inoculations was 7-days, virus-neutralizing antibody appeared after 5 days and reached levels 2-4 times those obtained with live vaccine alone. With longer intervals (up to 60 days) the enhancement of the immune response was even greater. It seems likely that use of the two-step method may reduce the incidence of post-vaccination encephalitis and clinical studies to determine the optimum conditions for safety and efficacy are at present being undertaken. (+info)
Smallpox eradication in West and Central Africa.(6/360)
Clinical observations on smallpox: a study of 1233 patients admitted to the Infectious Diseases Hospital, Calcutta, during 1973.
The paper presents clinical observations on 1 233 persons with smallpox who were admitted to the Infectious Diseases Hospital, Calcutta, in 1973. The disease was of the modified type in 53 patients (4.3%), the ordinary type in 717 (58.2%), the flat type in 249 (20.2%), and the haemorrhagic type in 214 (17.3%). The fatality of these types of smallpox was found to be 5.7%, 26.8%, 88.4%, and 98.1%, respectively, and the overall case fatality was 50.7%. The haemorrhagic type was found mainly among older patients and affected males more often than females. The vaccination status of 1 218 patients was known. Of these, 901 (73.9%) were unvaccinated and had a fatality rate of 53.4%, whereas the 317 (26.1%) vaccinated patients had a fatality rate of 36.5%. Among the 201 haemorrhagic cases, 145 patients were unvaccinated (16.09% of the total number unvaccinated) and 56 (17.67%) had been vaccinated. Of 34 patients vaccinated during the incubation period, 19 (41.1%) died, whereas of 18 patients who had been vaccinated after the onset of fever, but before the appearance of rash, 9 (50%) died. (+info)
The minimum protective level of antibodies in smallpox.
Blood samples from 57 contacts of 6 smallpox cases were tested for haemagglutination-inhibiting (HI) and neutralizing antibodies. All 6 contacts who subsequently developed smallpox were unvaccinated and had neutralizing antibody titres of 10 or less. However, 6 unvaccinated contacts with similar antibody levels did not develop smallpox. None of the 41 vaccinated contacts, regardless of their antibody level, contracted the disease. (+info)