Video S6 SIR epidemic on the EGP-immunized artificial social network. IV. In this video, we start an SIR epidemic from a fourth seed on the EGP-immunized artificial Jin-Girvan-Newman social network. The original network consists of 1,000 nodes and 1,584 links, whereas the estimated network EGP is based on consists of 475 nodes and 934 links. 67 separator nodes identified by the EGP procedure are removed from the original network, giving an immunized network with 1,359 links. (WMV) Strengthening systems for communicable disease surveillance: creating a laboratory network in Rwanda BACKGROUND: The recent emergence of a novel strain of influenza virus with pandemic potential underscores the need for quality surveillance and laboratory services to contribute to the timely detection and confirmation of public health threats. To provide a framework for strengthening disease surveillance and response capacities in African countries, the World Health Organization Regional Headquarters for Africa (AFRO) developed Integrated Disease Surveillance and Response (IDSR) aimed at improving national surveillance and laboratory systems. IDSR emphasizes the linkage of information provided by public health laboratories to the selection of relevant, appropriate and effective public health responses to disease outbreaks. METHODS: We reviewed the development of Rwanda's National Reference Laboratory (NRL) to understand essential structures involved in creating a national public health laboratory network. We reviewed documents describing the NRL's organization and record of test results, conducted site visits, and interviewed health staff in the Ministry of Health and in partner agencies. Findings were developed by organizing thematic categories and grouping examples within them. We purposefully sought to identify success factors as well as challenges inherent in developing a national public health laboratory system. RESULTS: Among the identified success factors were: a structured governing framework for public health surveillance; political commitment to promote leadership for stronger laboratory capacities in Rwanda; defined roles and responsibilities for each level; coordinated approaches between technical and funding partners; collaboration with external laboratories; and use of performance results in advocacy with national stakeholders. Major challenges involved general infrastructure, human resources, and budgetary constraints. CONCLUSIONS: Rwanda's experience with collaborative partnerships contributed to creation of a functional public health laboratory network. Communicable diseases remain the leading cause of illness, death and disability in African countries [1, 2] . Even though well-known, efficacious responses are available for the control and prevention of these diseases, the capacity for timely detection, confirmation and response actions needs reliable public health systems. To address the demand from countries for improved surveillance systems that provide relevant and accurate epidemiologic and laboratory information, the Member States of the World Health Organization (WHO) Regional Headquarters for Africa (AFRO) adopted a strategy in 1998 called Integrated Disease Surveillance and Response (IDSR) [2] . A major goal of IDSR is to strengthen district-level surveillance capacities for detecting, confirming and responding to priority diseases that afflict African communities. In the IDSR implementation framework, epidemiologic surveillance is linked with laboratory support in order to produce relevant information for taking public health action [3] .