In the early twenty-first century, measles was completely eradicated in the United States of America (USA) and almost eliminated in Canada. This was greatly due to most of the population being vaccinated against the virus. In 2018 and 2019, the USA and Canada experienced a rapidly developing measles virus outbreak due to growing debates about vaccine efficacy and side effects. Therefore, some people refused to vaccinate their children against measles, as well as many other life-threatening preventable diseases. This led to a major measles outbreak and health concern in the USA, Canada, and globally. Some countries including the Democratic Republic of the Congo (DRC) reported a significant number of cases and casualties resulting from measles, mainly due to the lack of funding for vaccines, as well as inadequate vaccination coverage in certain socio-demographic areas. People traveling from these countries can easily transmit the disease, though there has been a steep decline in cases since the travel ban due to coronavirus disease-2019 (COVID-19). The number of unvaccinated children currently in the USA and Canada has quadrupled since 2001. Over the past couple of years, most of the measles cases have been diagnosed in those who either did not receive the measles vaccine or complete the recommended doses of the vaccine. This paper reviews the measles outbreak, in recent years, among unvaccinated individuals in the USA, Canada, and globally.
Part of the book: Current Perspectives on Viral Disease Outbreaks
Since the pandemic began in China in December 2019, thousands of variants of SARS-CoV-2 have emerged globally since late 2020. The World Health Organization (WHO) defined the SARS-CoV-2 variant of concern (VOC) as a variant with increased transmissibility, virulence, and decreased response to available diagnostics, vaccines, and therapeutics. Areas of the emerging variant of concern arise from countries like the United Kingdom, South Africa, Brazil, and India. These mutations carry a lineage from N501Y, D614G, N439K, Y453F, and others, which are globally dominated by clades 20A, 20B, and 20C. SARS-CoV-2 VOC emerged after 11 months of evolution since the onset through massive human-to-human transmission with five major VOCs recognized by the WHO, namely Alpha, Beta, Gamma, Delta, and Omicron. Their emergence could be attributed to changing immunological dynamics in the human population, which has resulted in resistance or escape from neutralizing antibodies, or to mutations and/or recombinations that increase transmission or pathogenicity. This literature review intends to identify and report on SARS-CoV-2 variants that have evolved two years post-onset of the pandemic and their disease implications.
Part of the book: Current Topics in SARS-CoV-2/COVID-19