During the past three decades, since the 1988 World Health Assembly resolution to eradicate polio, the Global Polio Eradication Initiative (GPEI) efforts have decreased global polio incidence by 99.9%. GPEI efforts have benefitted over 16 million people who would otherwise have been paralysed, and approximately 1.5 million people whose lives would otherwise have been lost [1]. Now the task remains to tackle poliovirus transmission in its last few strongholds through parallel pursuits of wild poliovirus (WPV) eradication and vaccine-derived poliovirus (VDPV) transmission elimination [2,3]. There are 23 GPEI priority countries: 3 WPV-endemic (Afghanistan, Pakistan, Nigeria), 5 circulating VDPV (cVDPV) outbreak/active transmission, and 15 at-risk countries. Conflict, political instability, hard-to-reach populations, and poor infrastructure continue to pose challenges to eradicating the disease [2,3] (Photo 1). About half of all polio cases during 2009–2011 occurred due to international spread from endemic to polio-free countries [4]. In May 2014 the World Health Organization (WHO) declared the international spread of wild poliovirus as a Public Health Emergency of International Concern (PHEIC) per the IHR (2005) [4], and reiterated the concern during the 2018 the WHO IHR Emergency Committee meeting as the number of VDPV cases greatly exceeded the number of WPV cases in 2017 (96 vs. 22).

The 138th session of WHO's Executive Board on Jan 25, 2016, noted both the end of the 2014 Ebola crisis and the beginning of a global public health threat, the outbreak of Zika virus infection in the Americas.1 On Jan 15, 2016, the US Centers for Disease Control and Prevention advised pregnant women to refrain from travelling to countries affected by Zika, given a possible association between Zika virus infection with microcephaly and other neurological disorders.2 On Feb 1, 2016, WHO's International Health Regulations Emergency Committee declared the possible association between Zika virus infection and clusters of microcephaly and other neurological disorders as a Public Health Emergency of International Concern.3 With the spread of the arbovirus to more than 25 countries, Zika virus could be following the geographical spread of dengue and chikungunya, all of which are transmitted by the Aedes aegypti mosquito.1, 3 | The potential role of scheduled international mass gatherings in 2016 could exacerbate the spread of Zika virus beyond the Americas. In Brazil, the Rio Carnival on Feb 5–10 attracts more than 500 000 visitors, and on Aug 5–21 more than 1 million visitors are expected to go to the summer Olympics followed by Paralympic Games on Sep 7–18. Meanwhile, Saudi Arabia expects to host more than 7 million pilgrims from over 180 countries for the Umrah, between June and September, and the Hajj pilgrimage on Sept 8–13.4, 5 Saudi Arabia receives about 7000 pilgrims from Latin America annually.

Sickle cell disease (SCD) is a hemoglobinopathy and a life-long blood disorder characterized by red blood cells that assume an abnormal, rigid, sickle shape, which decreases the cells' flexibility and causes risk of various complications. About 7% of the world's population are carriers of the condition, and 300,000–400,000 affected children are born each year, making SCD the most common life-threatening monogenic disorder in the world1 (Figure 1). The highest frequency of SCD remains in tropical regions, particularly sub-Saharan Africa, India, and the Middle East, and in countries to which people from these regions have migrated. In the past 5 decades, because of migration and demographic changes, SCD has been observed with increasing frequency in previously low-incidence areas.2 There is marked variation in carrier frequency, not only between countries but also between regions within countries. For example, among the Bamba tribe in western Uganda, the carrier frequency is as high as 45%, whereas it is as low as 1%–2% in South Africa and on the North African coast.3