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A general disease transmission model is developed for a tick-borne disease for cattle. Both the tick and cow are possible hosts for the disease parasite. The two species are therefore classified as infected or uninfected. The tick individual is further classified as sedentary (off-host) or feeding (on-host). First conditions for the persistence of the tick population are investigated. A threshold quantity for the disease is derived which is dependent on both the tick and host population parameters and the two transmission rates: from ticks to cattle and vice versa. From the analysis persistence and non-persistence conditions for both the tick population and the disease are investigated. The effect of the presence of a second host species is introduced as an additional feature in the analysis.

There is vigorous controversy around whether HIV-infected women in developing countries should choose formula or breastfeeding for their infants. Formula eliminates HIV transmission but incurs risk of increased mortality, whereas breastfeeding has multiple benefits but entails risk of HIV transmission. International guidelines are available but need to be strengthened. This commentary summarizes data on the scale and rate of mother-to-child transmission (MTCT) of HIV through breastfeeding, and the hazards and benefits of breast- and formula-feeding. The case against providing free or subsidized formula to HIV-infected mothers is based on the following: it exacerbates disadvantages of formula feeding; compromises free choice; targets beneficiaries erroneously; creates a false perception of endorsement by health workers; compromises breastfeeding; results in disclosure of HIV status; ignores hidden costs of preparation of formula; increases mixed breastfeeding, which is an unsatisfactory method for all women; requires organization and management of programmes that are complicated and costly; and finally increases the 'spill-over' effect into the normal breastfeeding population. Recommendations to minimize these drawbacks include use of affordable antiretrovirals to reduce MTCT; investments in high-quality, widely available HIV counselling; support for choice of feeding; and exclusive breastfeeding for those who choose to breastfeed.

Political will or commitment toward the HIV epidemic has been lacking in most African countries. Although most countries are in denial, a few have moved into recognition of the epidemic. Only two countries, Senegal and Uganda, have moved into mobilization. Ineffectiveness is judged by increasing HIV prevalence rates and declining life expectancy. Countries without active national leadership to fight the epidemic have seen deterioration in these criteria. In addition to its toll in Africa, this epidemic threatens U.S. political, economic, and security interests. Political responses to manage the risks to the United States have revolved around much increased development assistance through traditional channels and financial support for the United Nations' Global Fund to Fight AIDS, Tuberculosis, and Malaria.

There is a rapid development of the 'second wave epidemic' of cardiovascular disease that is now flowing through developing countries and the former socialist republics. It is now evident from WHO data that coronary heart disease and cerebrovascular disease are increasing so rapidly that they will rank No. 1 and No. 5 respectively as causes of global burden by the year 2020. In spite of the current low prevalence of hypertensive subjects in some countries, the total number of hypertensive subjects in the developing world is high, and a cost-analysis of possible antihypertensive drug treatment indicates that developing countries cannot afford the same treatment as developed countries. Control of hypertension in the USA is only 20% (blood pressure <140/90 mm Hg). In Africa only 5-10% have a blood pressure control of hypertension of <140/90 mm Hg. There are varying responses to antihypertensive therapy in black hypertensive patients. Black patients respond well to thiazide diuretics, calcium channel blockers vasodilators like alpha-blockers, hydralazine, reserpine and poorly to beta-blockers, angiotensin-converting enzyme inhibitors and All receptor antagonists unless they are combined with a diuretic. A comprehensive cardiovascular disease (CVD) programme in Africa is necessary. There are social, economic, cultural factors which impair control of hypertension in developing countries. Hypertension control is ideally suited to the initial component on an integrated CVD control programme which has to be implemented. Primary prevention, through a population-based lifestyle linked programme, as well as cost-effective methods of detection and management are synergistically linked. The existing health care infrastructure needs to be orientated to meet the emerging challenge of CVD, while empowering the community through health education.

The experience of acquired immune deficiency syndrome (AIDS) in Africa is very different from that in the developed world. In the West, AIDS affects few people, and for those who are infected, it is an increasingly manageable illness. In Africa, huge numbers of people are being infected - mainly young adults through sexual intercourse. This is having a dramatic effect on key demographic indicators. Child mortality in some countries has doubled, while up to 25 years of life expectancy have been lost. The economic impact of AIDS is difficult to establish, but it is certainly leading to increased poverty in African families and communities. Development advances are being reversed, but the impact is incremental rather than catastrophic.