A new method for estimating the effort required to control an infectious disease

We propose a new threshold quantity for the analysis of the epidemiology of infectious diseases. The quantity is similar in concept to the familiar basic reproduction ratio, R0, but it singles out particular host types instead of providing a criterion that is uniform for all host types. Using this methodology we are able to identify the long-term effects of disease-control strategies for particular subgroups of the population, to estimate the level of control necessary when targeting control effort at a subset of host types, and to identify host types that constitute a reservoir of infection. These insights cannot be obtained by using R0 alone.     

A global alliance against tropical disease

The tenth annual meeting of the National Institute of Allergy and Infectious Diseases Internal Centers for Tropical Disease Research was held, 7-9 May 2001, in Bethesda, MD, USA.     

A serious canker disease of Eucalyptus in South Africa caused by a new species of Coniothyrium

Eucalyptus spp. are being propagated extensively as exotics in plantations in South Africa, and many other parts of the world. In South Africa, a number of diseases result in serious losses to this resource. This paper describes a new and very damaging stem canker disease, which has recently appeared on plantation-grown eucalyptus in South Africa. The disease, first noted in an isolated location in Zululand is now common in other parts of the country, and is typified by discrete necrotic lesions on stems. These lesions coalesce to form large, gum-impregnated cankers and malformed stems. The causal agent of the disease, as inferred from pathogenicity tests, is a new species of Coniothyrium described here as C. zuluense. This fungus is a serious impediment to eucalypt propagation in South Africa, and is most likely a threat to similar forest industries elsewhere in the world.     

Contribution of tuberculosis to slim disease in Africa.

OBJECTIVES--To assess the contribution of tuberculosis to the aetiology of the HIV wasting syndrome (slim) in Africa, a condition usually considered an enteropathy. METHODS--Clinical examination and representative necropsy study of adult patients positive for HIV. SETTING--Hospital medical wards in Abidjan, Ivory Coast. SUBJECTS--Adults positive for HIV. MAIN OUTCOME MEASURES--CD4 T lymphocyte counts before death, clinical and anthropometric data, and gross and microscopic pathology. RESULTS--Necropsy was done on 212 HIV positive adults. Tuberculosis was found in 41 of 93 with the clinical HIV wasting syndrome and in 32 of 119 without (odds ratio 2.1, 95% confidence interval 1.2 to 4.0). A significant association existed between the prevalence of tuberculosis at necropsy and the degree of cadaveric wasting (no wasting 25% (15/59); moderate wasting 40% (23/58); skeletal wasting 44% (42/95); P = 0.02). Wasting was also associated with a history of chronic diarrhoea, but no association existed between diarrhoea and tuberculosis. Median CD4 T lymphocyte counts were lowest in wasted patients irrespective of findings at necropsy and in those with chronic diarrhoea (< 60 x 10(6)/l). CONCLUSION--Wasting and chronic diarrhoea are late stage manifestations of HIV disease in Africa. The importance of tuberculosis as a contributing factor in the pathogenesis of the slim syndrome has been underestimated. In nearly half of patients dying with severe wasting, tuberculosis was the dominant pathological finding.     

A global stability criterion for simple control loops

Summary A method for studying biological control loops has been developed, which suffices to prove global stability for the Goodwin equations when the Hill coefficient is equal to 1. This holds for arbitrary reaction constants, even if time delays are included in the system. For a generalized class of repfessible systems, including the Goodwin Equations for >1, the method gives a sufficient condition for global stability, in terms of solutions of an algebraic equation in a single variable. When the criterion is not satisfied, the same equation gives bounds on any possible limit cycles. The method also shows that inducible systems with a unique equilibrium are globally stable. The system of equations studied allows each reaction rate equation to be non-linear, and to include a time delay.     

A new family of global protein shape descriptors

A family of global geometric measures is constructed for protein structure classification. These measures originate from integral formulas of Vassiliev knot invariants and give rise to a unique classification scheme. Our measures can better discriminate between many known protein structures than the simple measures of the secondary structure content of these protein structures.     

Italian Development Cooperation: the commitment for the struggle against malaria in Africa

The Italian Development Cooperation (DGCS) support the health reform process in Developing Countries, with the aim to provide populations in greatest need with access to decentralized health services. DGCS acts in close coordination with the donor community, United Nations' system and the World Bank, in agreement with sector-wide approach (SWAP) for health sector development. Since malaria control in endemic countries is a relevant component of the health system, DGCS is actively involved in the struggle against malaria in sub-Saharan Africa, supporting control activities and research capability strengthening. The following African countries are presently receiving bilateral support for antimalaria activities: Burkina Faso, Centre de Lutte contre le Paludisme in Ouagadougou; Ethiopia, community-based malaria control in Tigray; Eritrea, malaria control at national level in the framework of the Public Health and Rehabilitation Programme for Eritrea (PHARPE) initiative; Madagascar, malaria surveillance at national level; Tanzania, feasibility study for the support to the national malaria control programme. Support is provided by technical/financial assistance involving Italian academic and research institutions. On the multilateral channel, DGCS has provided regular contribution for WHO's work in malaria control and participates to the WHO Roll Back Malaria initiative. A new commitment to malaria is the trilateral joint scientific endeavour USA-Italy-Burkina Faso for the development and field testing of a candidate vaccine suitable for African populations.     

A new approach to reaching control for tetraplegic subjects

A simple upper limb control strategy to guide reaching in preparation to grasp for tetraplegic subjects is proposed. The control is based on new studies of self-paced human arm movements involving rotations about the shoulder and elbow joints. An experimental study of reaching, while grasping, by able-bodied humans, allowed us to reduce the dimensionality of the control vector from two to a single variable. This was accomplished by detailed analysis of the synergy between shoulder and elbow joint angles. This study examined only movements in teh horizontal plane. In the experiments we varied: (a) the shape of targets; (b) their position relative to the initial position of the hand; and (c) the speed of reaching. A synergy between shoulder and elbow joint angles was found in most analysed movements, and it was characterized by a scaling parameter between elbow and shoulder angular velocities. The scaling parameter was determined from the target position presented in the visual perceptive field and initial shoulder and elbow angles. The same experimental setup in studies with tetraplegics with retained shoulder movements showed that this natural synergism is preserved even though the motor and sensory components of the upper limb are reduced or absent. Tetraplegics originally showed a very different reaching pattern, but after short training sessions they developed a reaching behaviour which was similar to able-bodied subjects. The results presented can be used in the following way: a tetraplegic subject lacking elbow extension and flexion may be fitted with an assistive system which will be volitionally controlled only from ipsilateral shoulder movements. The assistive system can comprise either a motorized brace, or a functional electrical stimulation system applied to elbow flexors and extensors. With this system volitional movements at the shoulder would bring the hand into the correct position to accomplish an assisted grasping motion.