Typhoid in India: An Age-old Problem With an Existing Solution.

Enteric fever continues to impact millions of people who lack adequate access to clean water and sanitation. The typhoid and paratyphoid fever burden in South Asia is broadly acknowledged, but current estimates of incidence, severity, and cost of illness from India are lacking. This supplement addresses this gap in our knowledge, presenting findings from two years of surveillance, conducted at multiple sites between October 2017 and February 2020, in the Surveillance for Enteric Fever in India (SEFI) network. Results provide contemporaneous evidence of high disease burden and cost of illness-the latter borne largely by patients in the absence of universal healthcare coverage in India. Against a backdrop of immediate priorities in the COVID-19 pandemic, these data are a reminder that typhoid, though often forgotten, remains a public health problem in India. Typhoid conjugate vaccines, produced by multiple Indian manufacturers, and recommended for use in high burden settings, ensure that the tools to tackle typhoid are an immediately available solution to this public health problem.

The immunology of infection

The human immune system is composed of a collection of specialized cells and secreted proteins that allows the identification and removal of an invading pathogen, and in doing so limits host injury or death. This system is composed of innate and adaptive branches. It is important to recognize that although the innate and adaptive branches of the immune system differ fundamentally in their mechanisms of pathogen recognition, neither branch functions in isolation. In this article, we address how the innate and adaptive immune systems sense the presence of a pathogen, how the immune system then coordinates anti-pathogen effector functions to remove the pathogen, and how immunological memory functions to better protect its host against subsequent exposure to the same pathogen. Finally we consider how vaccines harness the immune system to induce protective immunity against infection and how controlled human infection models can inform our understanding of the immunology of infection.