Final answer:
The World Health Organization (WHO) is the key actor in global health within the United Nations, focusing on monitoring, promoting, and protecting health worldwide.
Step-by-step explanation:
The key actors in global health under the United Nations (UN) include various agencies, with the foremost being the World Health Organization (WHO). The WHO is instrumental in monitoring, promoting, and protecting health concerns worldwide. It provides leadership on critical health matters, shapes the health research agenda, and assesses worldwide health trends.
The WHO's comprehensive website offers updates on global health status, outbreaks, and current health news. While the ILO (International Labour Organization) and the UNHCR (United Nations High Commissioner for Refugees) play significant roles within their specific mandates, they are not primarily focused on health. The UNDP (United Nations Development Programme) and UNESCO (United Nations Educational, Scientific and Cultural Organization) also contribute to health indirectly through their work on development and education, respectively.