The selective, disease-specific nature of most current HSS strategies should not surprise us. True to their narrow focus, GHAs favour vertical programmes, which they consider the most efficient method to implement their activities. Furthermore, some actors appear to perceive health systems as “bottomless pits” in which external support disappears without a trace 
. Instead of investing in long-term strengthening of national stewardship capacity, they prefer lifting specific health system constraints that impede progress towards their objectives.
Two problems arise. First, the vague definition of HSS allows GHAs to stick the label “health system strengthening” on any health-related capacity strengthening activity. Such liberal use of the word, for reasons of political correctness, turns “HSS” into a meaningless container concept.
Second, there are still doubts regarding the effectiveness of many global health initiatives 
. No less important is the real risk of undermining existing services given the enormous financial leverage of some GHAs. In Uganda, for example, the total Ministry of Health budget for 2005 (US$112 million) was eclipsed by funding for AIDS from PEPFAR, the Global Fund, and the World Bank's Multi-Country HIV/AIDS Program (US$167 million). A similar situation occurred in Ethiopia. In both countries, the ministry had to outsource key management functions for these programmes due to inadequate capacity at national level 
Most GHAs now realise that their activities may also have negative effects (“system-wide effects”). These can be categorised as “duplication”, “imbalances”, and “interruptions” (adapted from Phyllida Travis and colleagues' framework 
is defined as multiplying efforts by developing parallel, non-integrated systems. The Multi-Country HIV/AIDS Program and PEPFAR are prime examples of agencies setting up parallel planning, operations, and monitoring systems 
. Parallel systems undermine local decision-making autonomy and lead to inefficiency 
. Duplication also includes setting up parallel delivery systems, for instance operated by non-governmental organisations. Imbalances
are defined as the creation of differences in resource allocation and utilisation within the health workforce. Often, GHAs draw personnel out of general health services into their programmes 
. These risks are not imagined: in Nepal, for example, health workers preferred to work with National Immunisation Day programmes because of the higher per diem rates 
. We define interruptions
as displacement of routine services due to programme activities such as training, fieldwork, administration, and accounting. In Cambodia, campaigns on HIV/AIDS, malaria, TB, and birth spacing led to reduced coverage rates of the routine immunisation programme