Case reports of OPV and human rights violations have been focused on individual experiences. Often, these are high profile cases and political bias and stance may influence case reporting, particularly in a society with high political tensions . The problem of under-reporting is substantial. In addition, case reports do not consider the health impact of OPV (including psychological torture) on family members or the long-term economic and social consequences for the community. Epidemiological tools offer an opportunity to assess systematically all forms of OPV and human rights violations at the population level and estimate their short- and long-term effects on physical, psychological and social well-being of the individual, family and the community [20–22].
With a pervasive feeling of pain and the perceived or real threat of OPV, there are psychological consequences of violence-related trauma and trauma-related disorders for family members of victims [23–27]. Therefore, we used the household as a unit to study the prevalence, risk factors and impact of collective violence on the family. This is the first epidemiological survey to confirm the elevated prevalence of injury, lifetime experience of OPV-related injury and pain complaints, CMR and U5MR in relation to the level of exposure to OPV and human rights violations in a complex setting. Both CMR and U5MR in Meherpur district are higher than the UNICEF figures for Bangladesh in 2006 (Table 2). The CMR in Meherpur district (17.9 per 1,000) remained close to the rate observed during the liberation war in 1971 (18.9 per 1,000) and the rate was also the same as the CMR in Zimbabwe, ranking 12th highest in the world in 2006. The CMR (0.49 per 10,000 per day) was also similar to that of most African countries at civil war (0.5 per 10,000 per day), while the U5MR (2.1 per 10,000 per day) had reached the WHO emergency threshold (2.0 per 10,000 per day). The violence-related mortality rate in Meherpur district was similar to the rate in a conflict zone in eastern Burma (Table 2). In addition, a majority of the study population suffered from pain. High mortality rate, injury rate and pain complaints of a population in the violence-prone areas should be taken as a warning sign of deteriorating public health.
Both qualitative and quantitative methods were used to determine the major risk factors for becoming a victim of OPV and human rights violations among the study population. Victimisation in Meherpur district is usually quite selective. A combination of individual, relational, community and societal factors, including variables such as age, household income level, area of residence, political party affiliation and patterns of social participation affect the risk of victimisation. Understanding these multilevel factors can help identify various opportunities for prevention .
Violence has remained inseparable from Bangladeshi politics and society. Bangladesh has gone through numerous political crises including two presidential assassinations, four coups, and at least 18 failed coup attempts since 1971 independence. The ongoing conflict between the leaders of the Awami League and the BNP is a prolongation of the three-decade hostility between these two families. The party elites instigated hatred of rival groups for political and economic gain; the struggle for power and resources between the two major parties has been blamed for the political polarisation [5, 30]. In the last decade, multiparty democracy has been restored in Bangladesh. Although State Fragility Index and Polity scores have improved , the democracy is far from consolidated. A 5-level Political Terror Scale  and the Cingranelli-Richards Human Rights Dataset  coded the practice of human rights of 190 countries in a particular year based on the yearly reports of the "US State Department Report" and Amnesty International. Both showed that violations of civil and political rights in Bangladesh have been systematically increasing from the 1990s and have become a routine practice of the security forces since 2001. This has jeopardised the multiparty democracy in Bangladesh. State-organised violence is by nature instrumental in achieving specific goals; the nature of state-organised violence must always be considered while studying violence-related injury and trauma in complex settings and post-conflict settings. In the absence of an effective international monitoring mechanism and preventive measures in complex settings and post-conflict settings, OPV and human rights violations are likely to be widespread. A similar situation has been also reported for Kashmir, India [34–36] and Karachi, Pakistan [27, 37–39]
The largest Islamic political party Jamaat-e-Islami Party was founded in pre-partition India in 1941. It has been against the independence of Bangladesh from Pakistan. One of the leaders of the Jamaat-e-Islami Party organised a militia in the Khulna division during the Bangladesh Liberation War in 1971 to assist the army of Pakistan. Until today, Khulna division, including Meherpur district, is still under the threat of Islamic extremists linked to Pakistan. The Jamaat-e-Islami Party has been in an alliance with the BNP and participated in a four-party coalition government during 2001-2006. Political polarisation is often blamed for attacks against Hindus because the main opposition party in 2001-2008, Awami League, has traditionally been the principal beneficiary of Hindu votes . Our study produced no evidence, however, that followers of Hinduism among the study population were at increased risk of OPV and human rights violations. A study also noted that no case of violence on religious differences was reported in Karachi, Pakistan .
The prevalence of conflict between families in villages is extremely high in Meherpur district (Table 1). It is also known that, in Bangladesh, vengeance, family or land disputes, dowry disagreements and political conflicts are the major causes of clashes between families and villages [6, 8, 30]. Based on the narratives of victim families obtained from focus group discussions, families can bribe the police or army to attack members of rival families. People from families with the highest income levels have a relatively higher risk of being arrested or detained than people from the poorest families, but there is no evidence that they are more likely to be tortured or executed. No proof can be derived from our study; however, our findings support the public opinion collected from focus group discussions and recent ethnographic research that Bangladeshi police extort money from the population [5, 26, 40]. According to Transparency International, 71% of the accused paid bribes to the police at an average rate of 5,718 Bangladesh taka (84 USD). Bangladeshi police arrest people without warrants and then use torture to extract bribes from the victims [30, 40]. The police offer to drop the charges in exchange for a bribe. If the negotiations do not yield anything lucrative, they torture the detainee. Richer families are more likely to arrange bribes to save victims from detention, and this could explain why the risk of being tortured or executed is lower for victims that come from the richest families .
Considerable geographical variation in OPV exposure was shown in the study areas, indicating 'hot spots' of violence and suggesting the responsibility of the local police force. The number of reported extrajudicial executions was higher in Meherpur Sadar upazila, and this tendency needs to be noticed. Traffic and trade between Bangladesh and India once flowed freely. Now, crossing an international border is highly regulated by the border security force. Criminals and terrorists also travel across the border, smuggling women, children or goods. The Bangladeshi government's decision to rely on the security force to tackle organised violence was initially widely welcomed; however, it soon came to be perceived as a convenient mechanism for unlawful income generation and political witch-hunting .
The leaders rely on the members of law enforcement agencies to wipe out the challengers to their power, and to crush those who have different political views and ideology or the criminals. The members of law enforcement agencies, however, have their own goals, independent from the leaders, and they could easily exploit the information and power advantage for their private interests. Pervasive corruption in the public sector in Bangladesh allows the members of law enforcement agencies to conceal their unlawful actions. The correlation of the level of human rights violations and sexual violence with the level of democracy and corruption has been examined and a similar pattern has been observed in India . OPV in Meherpur district is incited by a mixture of various motivations: political goals of leaders and private interests of the perpetrators (that is, reward or enjoyment of the agent), which support the theory of a principal-agent problem [42–44]. In summary, when the politics of organised crime and the organised crime of politics are mingled in Bangladesh, the victims are both economically and politically deprived.
In another paper, we will provide comprehensive information on the results of subsequent OPV screening at the mobile clinic, which allowed us to better understand the time, place, type and amount of exposure and to assess the association between exposure to OPV or human rights violations and physical and emotional fitness and social functioning of an oppressed population.
A community-based rehabilitation project was implemented by BRCT in selected villages in nine districts of Khulna division from 2005 to 2008. It had a specific focus on human rights education, community health and community development. We have established a population baseline in Meherpur district, reshaped the model of above community-based intervention and developed implementation strategies based on the knowledge generated from this study.
Limitations and strengths
A concern has been raised that carrying out such a survey can put the oppressed population at risk of state-organised violence. Therefore, it was absolutely crucial to work with a local NGO that had the capacity to provide both legal and health support to the victims. The BRCT and Task Force against Torture have provided legal support to victims, including making bail arrangements, providing legal advice and lobbying for legislative changes for many years. Both of them will be following up on the legal and health needs of victims once our study is completed. During the household survey, the majority of respondents were female. One of the strengths of our study is that the interviewers from the local NGO Manab Unnayan Kendra are very experienced in interviewing and providing consultation to victims of domestic violence and rape. Their experience helped to increase the survey response rate (99.9%). The household members were asked to remain to confirm the information provided. On the other hand, it made it embarrassing for the victims of sexual violence to reveal such an attack in front of their family members. Previous experience showed us that the victims of forced sexual contact or sexual torture were often in denial of tragedy or not ready to speak about it openly at the first or second approach by the social workers. They were likely to reach out for help afterwards. The brochures of the BRCT and Manab Unnayan Kendra were provided for their reference as resources that offer assistance or legal consultation for such types of victims. We believed that the numbers of victims of sexual violence in our survey were under-reported because of social stigma. The major limitations of this study are the cross-sectional and retrospective nature of the survey and there is concern about the accuracy and reliability of the survey participants' responses. Memory bias exists although a 10-year-recall is considered reliable [45, 46]. There is selection bias in that only one person from each household was interviewed. The head or the spouse of the head of the household may not necessarily know everything that happened to family members. To reduce the bias in responding, the other available household members were asked to remain to verify information. It is also possible that people in the village misunderstood the definition of each category of OPV and human rights violations. Finally, many of these limitations stem from the difficulty of conducting research in a society that is polarised politically. Some people are afraid to talk about the political violence and some party supporters accuse each other. The victim families were self-reported, and they may have expected to receive humanitarian aid. To avoid such expectations, interviewers did not mention the vouchers and subsequent mobile clinic activity and explained that there would be no compensation for participation in the survey. The reporting of injury and pain would have likely increased if survey participants were expecting free medical treatment from the BRCT, which established a pain treatment centre in the neighbouring district in Khulna division.