T he prevalence, cause, and pathobiology of pulmonary vascular disease in the developing world are not known, but estimates put the prevalence at 20 to 25 million. A major contributor is infectious disease. The present review examines the association between infectious disease and other causes in the developing world and pulmonary vascular disease and the need for further research in this area. Pulmonary Vascular Disease Associated With Schistosomiasis Schistosomiasis (Bilharzias) 1 is the third-leading endemic parasitic disease in the world, following malaria and amebiasis. More than 300 million individuals are infected, and another 600 million are at risk of infection. 2 The disease ranks higher in prevalence than HIV/AIDS. It is endemic in eastern South America, the Caribbean Islands, east Asia, and some parts of China and the Middle East, with sub-Saharan Africa being the most endemic area. It is a major public health problem that is closely correlated with socioeconomic conditions. Modern endeavors to develop and construct water schemes to meet local power and agricultural needs have increased the prevalence in many parts of the world. 2,3 Few countries have eradicated the disease or undertaken successful and sustainable control programs despite the collaborative efforts of local governments, the World Health Organization, the World Bank, the United Nations, and philanthropic organizations. Schistosomiasis is caused by flatworms. There are many species of Schistosoma. S mansoni infects Ͼ120 million people in Africa and Brazil. The final target of this species is the intestinal and hepatic circulatory system. S hematobium is endemic in Africa, the Middle East, and east Asia. It targets the genitourinary circulatory system. S japonicum, which is endemic in China and southeast Asia, affects the intestinal and hepatic circulatory system.

The lungs are the primary target of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, with severe hypoxia being the cause of death in the most critical cases. Coronavirus disease 2019 (COVID-19) is extremely heterogeneous in terms of severity, clinical phenotype and, importantly, global distribution. Although the majority of affected patients recover from the acute infection, many continue to suffer from late sequelae affecting various organs, including the lungs. The role of the pulmonary vascular system during the acute and chronic stages of COVID-19 has not been adequately studied. A thorough understanding of the origins and dynamic behaviour of the SARS-CoV-2 virus and the potential causes of heterogeneity in COVID-19 is essential for anticipating and treating the disease, in both the acute and the chronic stages, including the development of chronic pulmonary hypertension. Both COVID-19 and chronic pulmonary hypertension have assumed global dimensions, with potential complex interactions. In this Review, we present an update on the origins and behaviour of the SARS-CoV-2 virus and discuss the potential causes of the heterogeneity of COVID-19. In addition, we summarize the pathobiology of COVID-19, with an emphasis on the role of the pulmonary vasculature, both in the acute stage and in terms of the potential for developing chronic pulmonary hypertension. We hope that the information presented in this Review will help in the development of strategies for the prevention and treatment of the continuing COVID-19 pandemic.

Schistosomiasis is the most common parasitic disease associated with pulmonary hypertension. It induces remodelling via complex inflammatory processes, which eventually produce the clinical manifestation of pulmonary hypertension. The pulmonary hypertension shows clinical signs and symptoms that are not distinguishable from other forms of pulmonary arterial hypertension.

Ann Thorac Med, Official scientific journal of Saudi Thoracic society