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Influenza viruses utilize sialic acid-containing glycoconjugates as receptors. The distribution of receptors in host tissues has been investigated in many species to understand the ecology of influenza viruses in nature and the mechanisms of interspecies transmission of the viruses. On the other hand, lectins, which have been widely used to detect these receptor molecules, have many different characteristics from antibodies and thus, require special attention in interpreting the results of lectin staining. In particular, lectins derived from Maackia amurensis, which has been used to detect Siaα2-3Gal, the avian-type receptor for influenza viruses, have been used without fully understanding its characteristics. This led to some confusion in interpreting the distribution of influenza virus receptors in host tissues. How accurately do we know the distribution of avian-type receptors in host animals? In this article, we would like to suggest reviewing the influenza virus receptors by providing issues related to Maackia lectins.

B virus is a herpes virus that natutaly infects macaque monkeys. It is extremely neuropathogenic when infection occurs in humans. B virus infection has been reported only in laboratory workers and breeders of macaque monkeys in North America and the United Kingdom, and it is therefore recognized as a rare infectious disease. The first cases of B virus disease were reported in Japan in 2019 and in China in 2021, although no cases had been reported since 1997. Although B virus disease has not been reported for more than 20 years, the potential threat has always existed. The viral factors responsible for the strong neuropathogenicity of B virus to humans has not been identified. There are no reports of infection by contact with wild macaque monkeys, but the possibility can not been ruled out. In this paper, we describe its virological properties, findings from B virus disease from patient-reported cases, and the genotype of B virus.

In healthcare facilities, the initial response to emerging and reemerging infectious diseases, including COVID-19, requires systematic management. The first step is to establish an initial risk assessment and subsequent response flow, using a combination of triage and clinical examination for patients. Screening tests are performed for the early diagnosis of asymptomatic patients who are judged to be at low risk in the initial assessment. However, regardless of the test results, subsequent patient care should be taken cautiously to avoid inadequate initial evaluation at the time of admission, follow-up of symptoms and infection control measures after admission. The basic principle is standard precautions, with particular emphasis on compliance with hand hygiene. Universal masking for preventing transmission from asymptomatic/pre-symptomatic patients and reducing droplet emission and inhalation become the new essential precaution. For suspected/confirmed patients with COVID-19, surgical mask or N95 mask, gloves, gown, eye protection, and cap are basically used. The policy for personal protective equipment is made based on the medical environment of each facility. A negative pressure room is not always required but should be considered in high-risk environments, if possible. While the risk of transmission from the surface environment in a standard healthcare delivery system is limited, a continuous review of the facility environment is expected, considering the importance of ventilation.

Plant viruses, obligate parasitic pathogens, utilize a variety of host plant factors in the process of their infection due to the limited number of genes encoded in their own genomes. The genes encoding these host factors are called susceptibility genes because they are responsible for the susceptibility of plants to viruses. Plants lacking or having mutations in a susceptibility gene essential for the infection of a virus acquire resistance to the virus. Such resistance trait is called recessive resistance because of the recessive inherited characteristics. Recessive resistance is reported to account for about half of the plant viral resistance loci mapped in known cultivated crops. Eukaryotic translation initiation factor (eIF) 4E family genes are well-known susceptibility genes. Although there are many reports about eIF4E-mediated recessive resistance to plant viruses, the mechanistic insight of the resistance is still limited. Here we review focusing on studies that have elucidated the mechanism of eIF4E-mediated recessive resistance.

Coronaviruses are pathogens that infect many of animals, resulting in respiratory or enteric diseases. Coronaviruses constitute Nidovirales together with Arteriviridae. Most of human coronaviruses are known to cause mild illness and common cold. However, an epidemic of severe acute respiratory syndrome (SARS) occurred in 2002, ten years after SARS epidemic Middle East respiratory syndrome (MERS) emerged in 2012. Now, we face on a novel coronavirus which emerges in end of 2019. This novel coronavirus is named as SARS-CoV-2. SARS-CoV-2 is spread to worldwide within one to two months and causes coronavirus disease 2019 (COVID-19), respiratory illness. Coronaviruses are enveloped viruses possessing a positive-sense and large single stranded RNA genomes. The 5' two-thirds of the CoV genome consists of two overlapping open reading frames (ORFs 1a and 1b) that encode non-structural proteins (nsps). The other one-third of the genome consists of ORFs encoding structural proteins, including spike (S), membrane (M), envelope (E) and nucleocapsid (N) proteins, and accessory proteins. Upon infection of CoV into host cells, the translation of two precursor polyproteins, pp1a and pp1ab, occurs and these polyproteins are cleaved into 16 nsps by viral proteases. Structural proteins assemble to the vesicles located from ER to Golgi (ER Golgiintermediate compartment) and virions bud into the vesicles. Virions are released from infectedcells via exocytosis.

"Arbovirus" is a term for a virus transmitted to mammals by hematophagous arthropods; arboviruses; replicate in both mammals and arthropods. Since the life cycle of arboviruses is highly dependent on arthropods, control of the arthropods (vectors) is generally considered important for the control of arbovirus infection. Various pathogens that cause diseases in the medical and veterinary fields are grouped into arboviruses with a history of their discoveries since the early 20th century. Furthermore, because of recent advances in sequencing technology, new arboviruses have been discovered one after another. Here we would like to overview the known arboviruses and their infections.

The 2020 Nobel Prize in Physiology or Medicine was awarded to three researchers who contributed to the development of the disease concept ''non-A, non-B hepatitis'' and the isolation of its causative agent, hepatitis C virus (HCV). Technologies and experimental systems to analyze HCV have been greatly improved for these three decades, and the antiviral treatments against HCV have been developed. This review summarizes the effort to elucidate the HCV biology so far and the remaining subject to be solved in the future. I also introduce the studies to identify bioactive natural products by taking advantage of the HCV infection cell culture system.