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Hepatitis A in Japan between 2015 and March 2019
(IASR Vol. 40 p147-148: September, 2019)
Hepatitis A is an acute infectious disease caused by the hepatitis A virus (HAV), which belongs to the genus Hepatovirus of Picornaviridae. There is only one known serotype, which is classified into 6 genotypes, Ⅰ-Ⅵ. Viruses of genotypes Ⅰ to Ⅲ are detected in humans, with each genotype further divided into subgroups A and B. HAV is transmitted through the ingestion of contaminated food or water, or by direct contact with an infected person. In devel-oped countries with improved hygienic environments, such as water and sewage systems, large-scale outbreaks of hepatitis A are rare, but they have been reported among men who have sex with men (MSM) and persons who inject drugs (PWID).
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Rubella and congenital rubella syndrome in Japan as of May 2019
(IASR Vol. 40 p127-128: August, 2019)
Rubella is an acute infectious disease caused by the rubella virus, and the major clinical symptoms are rash, fever, and lymphadenopathy. Rubella virus infection of pregnant women may result in prenatal transmission to the fetus and the birth of an infant with congenital rubella syndrome (CRS), which manifests as varying symptoms, including heart defects, hearing loss, and cataracts. It may lead to death in cases associated with complications such as severe heart defects (see p. 129 of this issue).
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Severe fever with thrombocytopenia syndrome (SFTS) in Japan, as of June 2019
(IASR Vol. 40 p111-112: July, 2019)
Severe fever with thrombocytopenia syndrome (SFTS) was designated as a Category IV infectious disease under the Infectious Diseases Control Law on March 4, 2013 (see http://www.niid.go.jp/niid/images/iasr/35/408/de4081.pdf for notification criteria), and any physician who diagnoses SFTS is required to notify a local health center within 24 hours. In many cases, SFTS is a tick-borne infection. The causative virus was classified into the Genus Phlebovirus, Family Bunyaviridae, and was renamed “Huaiyangshan banyangvirus” of Banyangvirus Genus of Phenuiviridae Family by the International Committee on Taxonomy of Viruses (ICTV) in 2018. However, as it is widely referred to as the SFTS virus (SFTSV) in Japan and abroad, SFTS and SFTSV are used for the name of the disease and the virus, respectively, in this article. SFTS was first reported in 2011 by Chineses researchers and was subsequently confirmed to be endemic to Japan and South Korea. The incubation period is 5 to 14 days, and the major signs/symptoms in the early phase of the disease are fever, gastrointestinal symptoms, headache, and myalgia, which further associate with neurological symptoms (e.g., impaired consciousness) and bleeding symptoms (e.g., gingival bleeding and bloody diarrhea). Physical examination may reveal superficial lymph node enlargement and epigastric tenderness. Blood tests demonstrate leucopenia and thrombocytopenia, and increased AST, ALT, and LDH levels are observed by biochemical testing. In surviving patients, symptoms usually improve in approximately one week after onset and resolve after approximately two weeks. On the other hand, in fatal cases, multiple organ failure due to pathological conditions, such as respiratory and circulatory failure, and disseminated intravascular coagulation (DIC) is observed.
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Acute encephalitis in Japan, 2007-2018
(IASR Vol. 40 p93-94: June, 2019)
The weekly number of acute encephalitis cases has been reported since April 1999 as a targeted disease monitored at designated sentinel sites according to the National Epidemiological Surveillance of Infectious Diseases (NESID) based on the Act on the Prevention of Infectious Diseases and Medical Care for Patients with Infectious Diseases (the Infectious Diseases Control Law). In November 2003, the law was revised, and acute encephalitis was included in notifiable disease surveillance due to the need for early detection of unknown diseases such as emerging diseases (IASR 28: 339-340, 2007). As of 2019, acute encephalitis, excluding West Nile encephalitis, Western equine encephalitis, tick-borne encephalitis, Eastern equine encephalitis, Japanese encephalitis, Venezuelan equine encephalitis, and Rift Valley fever, which are included in Category Ⅳ infectious diseases, all physicians are required to notify the local public health center within 7 days from diagnosis as a Category Ⅴ infectious disease. The subjects of notification include acute encephalitis of unknown pathogen and cases presenting similar symptoms (hereinafter both referred to acute encephalitis). Cases that are obviously not infectious, such as febrile seizure, metabolic disease, cerebrovascular disorder, brain tumor, or trauma, are excluded. When notifiable disease surveillance of acute encephalitis began, if the original disease was a notification target, such as influenza encephalopathy or measles encephalitis, it was excluded from the report, but it became the subject of report from March 2004.
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Enterohemorrhagic Escherichia coli (EHEC) infection, as of March 2019, Japan
(IASR Vol. 40 p71-72: May, 2019)
Enterohemorrhagic Escherichia coli (EHEC) produces Verotoxin/Shiga toxin (VT/Stx) and/or possesses VT-encoding genes. The main signs/symptoms of EHEC infections are abdominal pain, watery diarrhea, and bloody diarrhea. Fever (>38°C) and/ or vomiting are occasionally observed. VT-producing EHEC can cause hemolytic uremic syndrome (HUS), which involves thrombocytopenia, hemolytic anemia, and acute renal failure; complications such as encephalopathy may occur, with potentially fatal outcomes.
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Measles in Japan, as of February 2019
(IASR Vol. 40 p49-51: April, 2019)
Measles is an acute infectious disease caused by the measles virus. The main clinical manifestations are fever, rash, and catarrh. The measles virus is transmitted as an aerosol, droplet or by contact, and its infectivity is markedly high. Measles patients frequently develop complications and may die if they develop pneumonia or encephalitis. Although it is rare, those who have caught and recovered from measles can develop subacute encephalitis with a poor prognosis known as subacute sclerosing panencephalitis (SSPE) several to 10-odd years after recovery (see p. 52 of this issue). The World Health Organization (WHO) estimated that 109,638 people, mainly children in developing countries, died from measles in 2017 (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6276384/pdf/06_mm6747a6.pdf).
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Echinococcosis in Japan, 1999-2018
(IASR Vol. 40 p33-34: March, 2019)
Echinococcosis is a zoonotic helminthiasis caused by cestodes of the genus Echinococcus. The life cycle of Echinococcus involves two host species: the definitive host, in which the adult tapeworms parasitize and undergo sexual reproduction, and the intermediate host that larvae infest and undergo asexual reproduction. In general, humans are not involved in transmission, but like the intermediate hosts, humans are infected by ingestion of eggs excreted by the definitive hosts. Larvae parasitized in parenchymal organs (mainly the liver) repeat proliferation and metastasis, leading to a fatal course unless treated appropriately. There are several species of the genus Echinococcus, but regarding public health, the important species are E. multilocularis, which causes alveolar echinococcosis (with domestic distribution), and E. granulosus, which causes cystic echinococcosis (without domestic distribution). Echinococcosis caused by both species is a Category Ⅳ infectious disease according to the Infectious Diseases Control Law, which took effect in April 1999, and physicians who diagnose echinococcosis must immediately notify the public health center with jurisdiction. In addition, due to the enactment of the revised Infectious Diseases Control Law in October 2004, notification by veterinarians who diagnose echinococcosis in dogs, which can be a source of transmission, was mandated.
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Carbapenem-resistant Enterobacteriaceae (CRE) Infection, Japan
(IASR Vol. 40 p17-18: February, 2019)
Carbapenem-resistant Enterobacteriaceae (CRE) infection is a broad term for infections caused by certain types of Enterobacteriaceae such as Escherichia coli and Klebsiella pneumoniae that are resistant to carbapenem and broad spectrum ß-lactam antibiotics. These antibiotics, such as meropenem, are most important for the treatment of Gram-negative bacterial infections. CRE mainly cause infections in patients with compromised immune systems, patients in their postoperative period, and patients who are administered antibiotics over a long period of time. Infection can result in infectious diseases, including respiratory infections, such as pneumonia, urinary tract infections, infections of surgical sites, skin, and soft tissues, medical device-associated infections (e.g. catheter-associated), sepsis, and meningitis, often causing hospital-acquired infections (HAIs). CRE can occasionally infect healthy individuals. In addition, there is often asymptomatic carriage of the bacteria such as in the digestive tract.
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Pertussis in Japan, as of November 2018
(IASR Vol. 40 p1-2: January, 2019)
Pertussis is defined as “acute respiratory tract infection caused by Bordetella pertussis” under the Japanese Infectious Diseases Control Law. The main symptom is a prolonged cough, and the severity is greater when newborns or infants are infected. Vaccination is important, and in Japan, in addition to the “adsorbed diphtheria-tetanus-acellular pertussis (DPT) vaccine”, the diphtheria-tetanus-acellular pertussis (DPT)-inactivated polio virus (IPV) vaccine, DPT-IPV, was added as a routine immunization in November 2012. The immunization schedule for DPT-IPV in Japan is composed of a primary series and a booster dose. For the primary series, three subcutaneous injections are administered with an interval of at least 20 days between each dose (recommended interval is 20-56 days) for those 3-12 months of age. For the subsequent booster, a subcutaneous injection is administered at least 6 months after the third dose of the primary series (recommended interval is 12-18 months after the third dose of the primary series) (http://www.niid.go.jp/niid/images/vaccine/schedule/2016/EN20161001.pdf: Routine/Voluntary Immunization Schedule in Japan, October 1, 2016). Immunity acquired by vaccination wanes 4-12 years after vaccination, and as the time since the last vaccination increases, those vaccinated may also become infected and develop disease onset. To protect infants from pertussis, some countries recommend and/or implement administration of a booster dose of the tetanus toxoid, reduced diphtheria toxoid, and acellular pertussis (Tdap) vaccine for adults, including adolescents and pregnant women (see p.14 of this issue). In developed countries, there have been concerns regarding unvaccinated infants who become infected and have severe outcomes, attributed to infections from adults and young adults who serve as a source of infection. In Japan, pertussis cases had until recently been reported from pediatric sentinel sites, and because the epidemiology of pertussis (including adult cases) could not be understood in a timely and accurate manner, the possibility of a delay in response existed.
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Respiratory syncytial virus infection, January 2014-September 2018
(IASR Vol. 39 p207-209: December, 2018)
Respiratory syncytial virus (RSV) is an RNA virus belonging to the family Pneumoviridae (see p. 213 of this issue). Pneumoviridae is composed of the genus Metapneumovirus, which includes human metapneumovirus (see p. 217 of this issue), and the genus Orthopneumovirus, which includes RSV. Based on phylogenetic analysis of the nucleotide sequence of the G gene, RSV is classified into two subgroups, RSV-A and RSV-B (see pp. 213 and 215 of this issue). RSV is transmitted via droplets or contact. Although at least 50% of infants become infected during their first year of life and nearly 100% by their second year, life-long immunity is not achieved. In infants, approximately 50% of pneumonia and 50-90% of bronchiolitis are due to RSV.