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Biomedical subjects

S Waner

Publications and source records attributed to S Waner.

15 recordsLinked to original sources
PubMed1999

Malaria protection measures used by in-flight travelers to South African game parks.

Malaria prevention in travelers depends upon dissemination of accurate information about malaria risk, prevention of mosquito bites, appropriate chemoprophylaxis use and knowledge of the symptoms of malaria. A study was undertaken of travelers to the Kruger National Park and private game parks in Mpumalanga Province, South Africa to investigate travelers knowledge, of malaria, chemoprophylaxis use, and experience of adverse events. In-flight self administered questionnaires were distributed and completed by travelers on flights returning to Johannesburg International Airport, from the malaria areas. The study was conducted during the highest malaria risk period during 1996. The Mpumalanga game parks are those most visited in South Africa and are found in the extreme northeast of the country, which adjoins Mozambique in the east and Zimbabwe in the north. This area is classified by the South African health authorities as being a high risk Malaria area.10 Chloroquine-resistant Plasmodium falciparum malaria has been described in this area.2,3 The Department of Health in South Africa recommends the use of mefloquine alone or the combination of chloroquine and proguanil, (doxycycline is prescribed for travelers in which the former antimalarials cannot be utilized), for visitors to this area during the high risk period for malaria, which extends from October to May.4 For the remainder of the year mosquito avoidance measures are recommended. Little is known about travelers' compliance with these recommendations and their knowledge of malaria. A study to explore these factors was undertaken as a joint initiative between the SAIMR travel clinic, Mpumalanga Department of Health, and the South African National Parks.

Adolescent↗
PubMed1999

Health risks of travelers in South Africa.

Large numbers of tourists visit South Africa every year. Travelers to urban areas are at little risk of contracting an infectious disease, however the adventure traveler is at increased risk. Yellow fever is not known to occur in South Africa. Malaria is endemic in Mpumalanga and KwaZula-Natal. Schistosomiasis is endemic in large parts of the country. Although rabies is found throughout the country, only a small number of human cases is reported. High risk areas are KwaZulu-Natal, the eastern Cape and Mpumalanga provinces. The incidence of human immunodeficiency virus (HIV) infection is high and counseling regarding sexually transmitted diseases is important. Sanitation of water is excellent in most large cities and towns; however travelers to rural areas should exercise caution. Arbovirus infections do occur but relatively few cases are reported. The hiker is at risk for tick bite fever and should be counseled. Since the abolition of apartheid, South Africa has been seen as an inexpensive, high quality destination by many tourists. In 1997, a total of 5,436,848 travelers from many different countries visited the country. Areas most frequently visited include Johannesburg, Cape Town, Durban, the Garden Route, Kruger National Park, KwaZulu-Natal and Pretoria. The most common reason for visiting the country was holiday (44%), followed by visiting friends and relatives (23%), business travel (27%) other (6%).1 Travelers, to the larger cities such as Johannesburg, Cape Town and Durban are at little risk of acquiring an infectious disease. The adventure traveler however is at greater risk as parts of the country are endemic for malaria, schistosomiasis, rabies, food and waterborne diseases, sexually transmitted diseases and arbovirus infections. Accidental deaths due to motor vehicle accidents and interpersonal violence are important health risks in South Africa. Travelers visiting popular attractions are at significantly lower risk. However this has never been quantified. This review aims to address the occurrence of infectious diseases and attempts to give guidelines to practitioners caring for travelers.

Communicable Disease Control↗
PubMed1999

Antimalarial prophylaxis--use and adverse events in visitors to the Kruger National Park.

OBJECTIVES: To determine the use of antimalarial prophylaxis and the relative frequency of adverse events with different regimens in visitors to the Kruger National Park. DESIGN: Retrospective postal survey of a cohort of 7,397 visitors during April 1996. Telephonic interviews were conducted with all respondents who reported neuropsychiatric adverse events necessitating medical attention, and their medical caregivers. RESULTS: The most commonly used regimens were chloroquine and proguanil in combination (C&P) (35.6%) and mefloquine (18.4%). However, non-recommended regimens were also used by travellers to this chloroquine-resistant area, including chloroquine alone (15.7%). Adverse events were reported by 23.8% of travellers and were more common in the C&P group than the mefloquine group (28.9% v. 25.0%, P = 0.0100). Gastro-intestinal side-effects were significantly more common in the C&P group (nausea (P = 0.0170), diarrhoea (P = 0.0008), mouth ulcers (P = 0.0000)), while neuropsychiatric side-effects were more common in the mefloquine group (depression (P = 0.0000), light-headedness (P = 0.0009), anxiety (P = 0.0060)). Only 30% of travellers reported using antimalarial drugs both regularly as prescribed and for 4 weeks after leaving the malaria area. The most commonly reported reason for changing prophylaxis was advice from a physician or pharmacist (41.9%). CONCLUSIONS: Health professionals providing medical advice to prospective travellers to malarious areas must tailor recommendations based on the balance between malaria risk in a specific geographical area and the benefits and tolerance of protective measures. Mosquito-avoidance measures should always be advocated, but counselling on antimalarial prophylaxis will be guided by the malaria/prophylaxis (serious adverse events) risk ratio. Where drug measures are indicated, the importance of their correct use should be emphasised.

Antimalarials↗
PubMed1998

Risk of malaria in visitors to the Kruger National Park, South Africa.

BACKGROUND: The risk of malaria to visitors to South Africa's nature reserves is unknown. Current recommendations for travelers are based on malaria incidence rates in local communities. These rates may well overestimate travelers' malaria risk and lead to unnecessary use of antimalarial prophylaxis with associated drug-related adverse events. This study investigated the incidence of malaria in visitors to South Africa's Kruger National Park (KNP). METHODS: Postal questionnaires were sent to the cohort of visitors staying in the KNP during April 1996, 6 to 8 weeks after they returned to their homes. Nonrespondents received duplicate questionnaires 8 weeks later. Responses from 3267 groups, representing 11,107 visitors (56. 8%) allowed determination of the malaria attack rate in this group of travelers and assessment of associations between malaria risk and a number of factors, including type of accommodation used during the visit; duration of stay; use of chemoprophylaxis; and use of personal protection measures. All travelers indicating that they had suffered an episode of malaria following their visit were telephonically contacted and their health providers traced to determine the basis of diagnosis and clinical outcome. RESULTS: One clinically suspected and four confirmed cases of Plasmodium falciparum malaria among the visitors suggest a low attack rate of 4. 5 cases per 10,000 visitors during April, the highest risk month for malaria in South Africa. No association was found between malaria risk and accommodation type, duration of stay, use and type of chemoprophylaxis, and use and number of personal protection measures. CONCLUSIONS: These findings confirm the importance of careful assessment of local malaria risk before individualized advice is provided to travelers.

Adult↗
PubMed1997

A Study to Determine Susceptibility to Hepatitis A of Travelers from South Africa.

Hepatitis A is an important cause of acute hepatitis in travelers to developing countries. In 1991, 33 million persons living in industrialized countries traveled to developing countries where hepatitis A is highly endemic (World Tourism Organization, unpublished data, 1993). Reports indicate that 40-50% of cases of hepatitis A infection in the United Kingdom,1 Switzerland2 and Sweden3 are associated with recent international travel. The disease is usually benign, but the severity increases with age.4 Because the disease is enterically transmitted, occurrence is related to water quality and level of sanitation. In developing countries, with poor water quality and sanitation, especially in the tropics where hepatitis A is endemic, exposure is virtually universal before the age of 10 years.4 In developed countries with good food and water hygiene, the rate of exposure to hepatitis A in children is low. The rate of seropositivity increases slowly during early adulthood and reaches moderate levels during late adulthood.5 Studies have demonstrated the higher prevalence among people who live in poor, overcrowded conditions.6 Travelers going from low incidence countries to endemic areas are particularly at risk for acquiring hepatitis A, especially if they stay for extended periods.7 The risk that Danish travelers to North Africa would acquire hepatitis A was estimated to be 3.5 per 10,000, and this population accounted for at least 20% of all cases of hepatitis in Denmark. Similarly, Germans traveling or living in tropical countries have a 40 times higher risk of acquiring hepatitis than do groups living at home.8 The pattern in South Africans ranges from minimal exposure to hepatitis A in childhood in populations with good water quality and sanitation (mainly white), to high exposure in those exposed to poor water quality and sanitation in childhood (mainly black). Hepatitis A vaccine has been found to be effective in reducing the incidence of infection in travelers. After the introduction of hepatitis A vaccine into Switzerland in 1992, there has been a reduction by 15% in the cases of imported hepatitis A.9 Hepatitis A vaccine should be offered to South African travelers to high risk areas.10,11 However for the vaccine to be the most cost-effective, it would be important to identify groups of travelers who would benefit from empiric vaccination as opposed to other groups who should undergo screening prior to vaccination. This study was undertaken to establish the seroprevalence of hepatitis A in the South African traveler and to identify groups of travelers that should be vaccinated.

Journal Article↗
PubMed1989

Evolutionary learning and hierarchical Markov systems.

The observation is made that various forms of evolutionary learning systems and classical evolutionary processes can be formally described as hierarchical systems of Markov processes. This leads to a simplification of issues such as convergence criteria and limiting behavior of such systems. The hierarchical structures in question are derived from the notion of rules and meta-rules for moving on graphs studied previously.

Biological Evolution↗
PubMed1988

Automata with hierarchical control and evolutionary learning.

We propose an automata-theoretical framework for structured hierarchical control, in terms of rules and meta-rules, for sequences of moves on a graph. This leads to a notion of a "universal" hierarchically structured automaton mu which can move on a given graph in such a way as to emulate any automaton which moves on that graph in response to inputs. This emulation is achieved via a mapping of the inputs in the given automaton to those of mu, and we think of such a mapping as an encoding of the given automaton. We see in several examples that efficient encodings of graph-search algorithms correspond to their natural hierarchical structure (in terms of rules and meta-rules), and this leads one to a precise notion of the "depth" of an automaton which moves on a given graph. By way of application, we discuss a proposed structure of a series of stochastic neural networks which can learn, by example, to encode a given sequence of moves on a graph, so that the encoding obtained is structurally the "natural" one for the given sequence of moves. Thus, such a learning system would perform both structural pattern recognition (in terms of "patterns" of moves), and encoding based on a desired outcome.

Algorithms↗
PubMed1985

Low dissipation computing in biological systems.

Biological systems frequently need to solve many computationally hard decision and optimization problems. The solution of these problems by digital computers as presently understood requires exponentially large energy dissipation. This severely restricts the ability of digital computers to attack such problems. We shall show that only polynomial dissipation is required to solve these problems adequately by "physical annealing", as realized in the genetic system, making these problems tractable energetically.

Biometry↗