Infectious Deseases
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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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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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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].
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Varicella/Herpes zoster: epidemiological trends and vaccines
（IASR Vol. 39 p129-130: August, 2018）
Varicella zoster virus (VZV), which belongs to the alpha herpesvirus subgenus of the herpesvirus family, is an etiologic pathogen of varicella (chickenpox) and herpes zoster (HZ). Varicella occurs in individuals infected with VZV for the first time causing maculopapular rashes to develop on all skin surfaces after the approximately 2-week incubation period (10-21 days), which then become vesicles. Varicella is characterized by the mixed presentation of macular, papular, vesicular, and encrusted lesions over the entire body and is often accompanied by fever. Varicella is a febrile rash syndrome that is common in childhood with a good prognosis. Individuals are infected with VZV through direct contact, droplet, and air-borne routes, and it is highly transmissible. Complications, such as secondary bacterial infections of the skin, pneumonia, meningitis, encephalitis, and cerebellar dysfunction, may occur. Varicella is designated as a Class II school infectious disease in the School Health and Safety Act, and school attendance is prohibited until all exanthem become encrusted. Varicella in adults is often severe, and for immunocompromised patients, it is extremely serious and can be life-threatening.
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Pneumococcal infections in 2017, Japan
(IASR Vol. 39 p107-108: July, 2018)
Streptococcus pneumoniae is a gram-positive diplococcus and one of the major respiratory pathogens. S. pneumoniae colonizes the nasopharynx of 40 to 60% of infants, and nasopharyngeal carriage plays a pivotal role in horizontal transmission of this pathogen in the community. The capsular polysaccharide (CPS) on the bacterial surface is the most important virulence factor and is also the antigenic determinant of serotypes. Currently, 97 serotypes are known, and the complement-dependent opsonization induced by the serotype-specific antibody is the major host defense mechanism against pneumococcal infections.
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Viruses detected from aseptic meningitis patients in Japan, through 2017
(IASR Vol. 39 p89-91: June, 2018)
Aseptic meningitis is often characterized by symptoms of acute onset of fever, headache, and vomiting, but may also present with meningeal signs, such as a stiff neck and Kernig’s sign. However, it is often the case that such manifestations may not be apparent in newborns or infants. The differentiation from bacterial meningitis is clinically very important, and, in addition to a negative result of bacterial detection from the cerebrospinal fluid (CSF), the following CSF tests are useful for the differentiation: first pressure, cell count and fractionation, CSF/serum glucose ratio, and protein quantity. Aseptic meningitis is caused by a variety of pathogens, and among viruses, enteroviruses are the most frequent, followed by the mumps virus. Enteroviruses detected in humans are classified into four species (Enteroviruses A to D), and Enterovirus B (echovirus, coxsackievirus group B) is the most frequently detected in patients with aseptic meningitis, followed by Enterovirus A [e.g., enterovirus A71 (EV-A71)].
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Enterohemorrhagic Escherichia coli (EHEC) infection, as of March 2018, Japan
(IASR Vol. 39 p71-72: May, 2018)
Enterohemorrhagic Escherichia coli (EHEC) is an important diarrheagenic E. coli, which 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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Rubella and congenital rubella syndrome in Japan as of January 2018
(IASR Vol. 39 p29-31: March, 2018)
Rubella is an acute infectious disease caused by rubella virus. The three major clinical signs of rubella are rash, fever, and lymphadenopathy. Although the symptoms of rubella are generally mild, serious complications, including encephalitis and thrombocytopenic purpura, can occur in rare cases. Rubella virus infection in susceptible pregnant women can result in prenatal transmission to the fetus. In particular, maternal infections that occur before a gestational age of 20 weeks can cause infants to be born with congenital rubella syndrome (CRS), which manifests as various signs/symptoms, including heart defects, cataracts, hearing loss, low birth weight, thrombocytopenic purpura, and psychomotor retardation (see p.33 of this issue). Effective and safe vaccines are available for preventing rubella and CRS.
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Hansen’s disease (Leprosy)
(IASR Vol. 39 p15-16: February, 2018)
Hansen’s disease (leprosy) is an infectious disease caused by the acid-fast bacillus Mycobacterium leprae. It mainly affects the skin and peripheral nerves. Until an effective treatment was available (until approximately the late 1940s), patients and their families faced stigma and discrimination due to the severe disfigurements of the face and extremities caused by the disease. Misconceptions, stigma, and discrimination towards patients and the disease have not been fully eliminated to this day.
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Invasive meningococcal infection, April 2013-October 2017, Japan
(IASR Vol. 39 p1-2: January, 2018)
Neisseria meningitidis is a gram-negative diplococcus. It can be isolated from the nasopharynx of healthy persons, albeit infrequently, and is transmitted by droplet aerosol or secretions from colonized persons. There are four classifications of invasive infection, namely, bacteremia without sepsis, sepsis unassociated with meningitis, meningitis and meningoencephalitis. Development of sepsis has poor prognosis. Waterhouse-Friderichsen syndrome is an acute fulminant form, manifesting as adrenal bleeding and/or systemic shock. Noninvasive presentation includes various manifestations, such as pneumonia and urethritis. Incubation period ranges from 2-10 days (average of 4 days) and the disease onset is sudden.