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This year was full of fascinating discoveries. New viruses were identified, and others were associated with new and old diseases. Milestones were reached in the battle against viral diseases, and yet viral outbreaks continued to frighten the world. Scientists uncovered novel technologies to diagnose viral infections, and to deliver gene therapies that achieved results we could not imagine decades ago. Virologists learned more about the role the human microbiome plays in viral infection. This is the year in review with the findings that shaped 2019 in the field of viruses.
New diseases and viruses
A new polio-like disease outbreak (acute flaccid myelitis, or “AFM”) emerged in the United States in the last years, with more than 500 cases reported by CDC. AFM brought us back memories and fears from the early 1940s in the US, where after a few years of small polio outbreaks in American children, many more episodes would come in the following years paralyzing more than 50,000 children at the peak of the1952 epidemic. In 2019, epidemiological and immunological studies associated the new polio-like disease with other picornaviruses, enterovirus D68 and A71. Human herpesviruses 6 (HHV-6) and Epstein-Barr virus (EBV) were associated with multiple sclerosis in humans. HHV-6 and HHV-7 were also linked to Alzheimer’s disease. Adenovirus C was associated with type I diabetes, and human papillomavirus infection correlated with increased odds of breast carcinoma. An entire new family of viruses, the redondoviridae, was found in the human lung during metagenomic analyses. The “medusavirus”, was identified in a hot spring in Japan. The medusavirus infects amoeba cells and its genome is among the largest and more complexed viral genomes ever found, with genes encoding all types of histones. Scientists demonstrated for the first time that a non-enveloped insect RNA virus, “Providence virus”, can also infect plants and mammalian cells, suggesting that plants could act as reservoirs of human viruses. Another study reported that more viruses than previously elucidated (about 30 different viral species) can be found in human semen. The list included viruses of known routes of sexual transmission, such as HIV or HTLV-1, and also others like Lassa, Zika or Dengue. Proof of sexual transmission of dengue virus was confirmed in 2019 for the first time.
New viral therapies
This was not a great year for FDA approvals for antiviral therapies. 54 new drugs were approved by the FDA in 2019, included 48 new small-molecules. None of them target viral diseases. Xofluza (baloxavir marboxil), an inhibitor of the influenza virus polymerase acidic endonuclease, was approved in October 2018 for the treatment of acute uncomplicated influenza, in healthy people 12 years and older. In October 2019 Xofluza was also approved for the treatment of people at high risk of influenza complications, including those with asthma, chronic lung disease, diabetes, heart disease and obesity. During 2019 we heard great news about the first anti-influenza drug approved in more than 20 years. Therapy with Xofluza was found useful at preventing flu transmission in the household environment, reducing the chances of transmission in individuals under the same house by over 85%. However, in November, results from a study reported alarming rates of baloxavir-resistant strains, especially in children. The appearance of drug-resistance is common among RNA viruses, but the study found the troublesome ability of the virus to mutate without compromising its "viral fitness". Some scientists questioned the use of the antiviral in children, where resistant rates were significantly higher......
