国立感染症研究所

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The topic of This Month Vol.40 No.6(No.472)

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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The topic of This Month Vol.40 No.5(No.471)

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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The topic of This Month Vol.40 No.4(No.470)

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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The topic of This Month Vol.40 No.3(No.469)

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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The topic of This Month Vol.40 No.2(No.468)

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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The topic of This Month Vol.40 No.1(No.467)

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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The topic of This Month Vol.39 No.12(No.466)

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.

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The topic of This Month Vol.39 No.11(No.465)

Influenza 2017/18 season, Japan

(IASR Vol. 39 p181-183: November, 2018)

The 2017/18 influenza season (from week 36 in September 2017 to week 35 in August 2018) was characterized by the predominance of the influenza B/Yamagata lineage, followed by A/H3 and A/H1pdm09 subtypes.

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The topic of This Month Vol.39 No.10(No.464)

Malaria, Japan, 2006-2017

(IASR Vol. 39 p167-169: October, 2018)

Malaria is a protozoan infection transmitted by the bite of anopheline mosquitoes, and with more than 200 million infections and approximately 500,000 deaths annually, it is the world’s most burdensome infectious disease.  The causative agents for human malaria are four species of the genus Plasmodium, namely P. falciparum, P. vivax, P. ovale, and P. malariae, which cause falciparum malaria, vivax malaria, ovale malaria, and malarie malaria, respectively.  Falciparum and vivax malaria account for more than 90% of notified cases, and the other two are uncommon.  The major signs and symptoms of malaria are fever, splenomegaly, and anemia.  In falciparum malaria, severe complications, such as cerebral malaria, acute renal failure, and acute respiratory distress syndrome, occur because of occlusion of blood capillaries in organs by sequestration of parasitized red blood cells.

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The topic of This Month Vol.39 No.9(No.463)

HIV/AIDS in Japan, 2017

(IASR Vol. 39 p 149-150: September, 2018)

HIV/AIDS surveillance in Japan started in 1984.  Surveillance was conducted under the AIDS Prevention Law between 1989 and March 1999, and since April 1999 has operated under the Infectious Diseases Control Law.  Under the law, physicians shall notify all diagnosed cases (see http://www.niid.go.jp/niid/images/iasr/34/403/de4031.pdf).  The data in this article were derived from the annual report of the National AIDS Surveillance Committee for the year 2017 [published by the Tuberculosis and Infectious Diseases Control Division, the Ministry of Health, Labour and Welfare (MHLW), http://api-net.jfap.or.jp/status/index.html].

Copyright 1998 National Institute of Infectious Diseases, Japan

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