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About exanthema subitum

■We publish this article so that summary, many people can refer to about contents from literatures of textbook. We do not necessarily offer the latest knowledge and do not present opinion as Yokohama-shi. ■In addition, we cannot cope with question as the staff who studies mainly about this matter is not placed. In addition, please consult with medical institution about individual diagnosis and treatment.

Last update date July 16, 2019

The fashion?

It is infectious disease to be seen all over the world. It is mainly (Homo sapiens) caused by herpesvirus 6-B (HHV6-B). In the United States of America, 12-30% of children suffer from exanthema subitum. However, 86% of children get antibody for HHV6-B by 1 year old, and most children acquire by 4 years old. Either lacks in symptom peculiar to exanthema subitum such as fever, rash even if infected with HHV6-B in the United States of America, and there seem to be considerably cases of subclinical infection that symptom that seems to be symptom does not appear. It is said that typical rash does not appear in 70% even if infected with HHV6-B in the United States of America. Outbreak of exanthema subitum is seen, but, in the United States of America, autumn has much outbreak in spring throughout the year.

There is study (references 4) of French Ranger and others which studied having antibody or not for HHV6-B of pregnant woman of 11 countries. 76% are that 92% had antibody for HHV6-B in Ecuador in low country in France with 20% are high countries in Morocco. About infection of HHV6-B, there seems to be considerably difference by country and race.

Outbreak of exanthema subitum is seen, but, in Yokohama-shi, seasonal change is not seen throughout the year.
It is the Japanese situation that is similar in total.

Exanthema subitum is five kinds of Pediatrics fixed point grasp diseases in Infectious Disease Law, and, in Japan, patient outbreak is grasped with Pediatrics fixed point medical institution of whole country about 3,000 (as for the report standard of exanthema subitum from this page). The number of the age-specific outbreak reports is just what of lower graph in the patients with exanthema subitum year per national Pediatrics fixed point medical institution of 2,000-2,006 years. In age, there are the most babies under 1 more than six months after birth. Then, there is much outbreak of baby within 1-year-old infant, six months after birth.

Graph (the number of the outbreak reports age-specific in the patients with exanthema subitum year per national Pediatrics fixed point medical institution of 2,000-2,006 years)

What kind of disease do you have?

There is study (references 5) of Japanese Asano and others which studied symptom, progress of 176 affected children of exanthema subitum which confirmed infection by HHV6-B. Infants of mean age of the month 7.3 months have fever in 98%. Average of the most hyperthermy of fever reaches 39.4 degrees. Fever lasts an average of 4.1 days. Heat falls, and rash such as red spot or papules develops in 98%. It is part of face and trunk that rash develops and disappears in an average of 3.8 days. As symptom except fever, rash, light diarrhea 68%, cough 50%, swelling 31% of lymph nodes of neck, great fontanel bulge 26%, convulsions (convulsions) are seen in 8%.

The incubation period is about nine days (5-15 days).

Frequently, it is accompanied by diarrhea. As we may become slightly spin-drying because of diarrhea and fever, let's supply moisture enough.

Besides, there are various kinds of infectious diseases to be accompanied by fever and rash, but we are usually running a fever, and rash appears. It is characteristic of exanthema subitum that heat falls, and rash develops after temperature became normal. Clear diagnosis is difficult, and, during period only for the first fever, diagnosis of exanthema subitum often goes down after rash developed. Exanthema subitum is existence of the youngest child of infectious disease with rash. Exanthema subitum is also called sixth disease (sixth disease) in English. As for the Measles, as for the German Measles (Rubella), third disease, erythema infectiosum are also called fifth disease the first illness.


Pathogen is (Homo sapiens) herpesvirus 6-B (HHV6-B). When we were infected with HHV6-B for the first time, we often become sick as exanthema subitum. There are considerably individual differences in symptom of this time, and it is said with case and subclinical infection that rash does not appear, and there may not be symptom. In comparison with Europe and America, symptom of typical exanthema subitum seems to be easy to come out in Japanese then. HHV6-B continues multiplying with salivary gland of patient after the first infection (exanthema subitum) of this HHV6-B was cured, and HHV6-B continues appearing in saliva. It is thought that infection to neighboring people happens by HHV6-B in this saliva.

In addition, HHV6-B which there was in dormancy state in the body after the first infection (exanthema subitum) of HHV6-B was cured with immunity is controlled people who are in a state activates again and, like person who received AIDS patient and zokii*, may wake up infection. When it is usual and has impossible infection in people who are in a state that immunity was controlled, we say the infection with fence-sitting (fence-sitting) infection. HHV6-B is known as virus which may cause fence-sitting infection to people who are in a state that immunity was controlled with (Homo sapiens) cytomegalovirus and HHV7, HHV6-A. There is the side that studies such as HHV6-B advanced to in study of fence-sitting infection of people who are in a state that immunity was controlled.

Well, drug-related hypersensitivity syndrome (DIHS: drug-induced hypersensitivity syndrome) rises fever, liver trouble, white blood-cell count and is seriously ill drug-caused skin eruption with lymphadenopathy. We produce reactivation of HHV6-B 2-3 weeks after after onset and may see revival of symptom for this drug-related hypersensitivity syndrome in many cases. Cause drug is often anticonvulsions agent, jiafenirusurufan, sarazosurufapirijin, allopurinol, minocycline, mexiletine, and there are many 2-6 weeks for internal use time to onset.

It is high, and antibody titer for HHV6-B decreases after the birth in newborn babies in 3-9 months and it rapidly rises afterwards and keeps just high value until 60 years or older. In this, baby holds antibody for HHV6-B from mother for a while after we are born, but shows that the antibody disappears, and most infect HHV6-B by 1 year old.

HHV7 (human herpesvirus 7) is considered to be pathogen of exanthema subitum, too. But there is less frequency than HHV6-B, and age to be infected is higher.

HHV6 is classified in HHV6-A(variant A) and HHV6-B(variant B). HHV6-B is known as pathogen of exanthema subitum, but does not understand pathogenicity of HHV6-A for person that immunity is not controlled well. But, in African Zambia, HHV6-A is one of the pathogens of exothermicity disease that infants suffer from for the first time in life. In infants infected with HHV6-A, the respiratory tract infectious disease symptom or rash were seen as well as fever. In addition, HHV6-A and HHV6-B are known to people who are in a state that immunity was controlled as virus which may wake up fence-sitting infection like person who received AIDS patient and zokii*. In people who are in a state that immunity was controlled, we have fever, rash, pneumonia, hepatitis, encephalitis and may result in death. In zokii*go 2-4 weeks, we may raise infection and reactivation of HHV6-A and HHV6-B. Furthermore, disease that HHV6-A and HHV6-B may be connected with etiology includes multiple sclerosis. In addition, unlike HHV6-B, HHV6-A does not multiply with salivary gland of patient.

It is ... for the prevention

There is no Vaccinations (vaccine) of exanthema subitum.

Because case that baby starts is most, in the United States of America, it is called "baby measles" (baby measles) commonly. There are not regulations of school attendance standard because we are not thinking about the Japanese school hygiene method targeting at babies.

What prevent infection of baby by HHV6-B is always difficult if HHV6-B appears in saliva of parent and brothers whom there is close of baby. Baby will be infected with HHV6-B when immunity from mother was gone. Therefore disease to generate high heat only after baby being born is often exanthema subitum.


  1. Mikiko Fujiyama, Koji Hashimoto: DIHS, drug-induced hypersensitivity syndrome: Japanese medical affairs Courier No. 4275 (April 1, 2006), p.62-66.
  2. Giuseppe Gentile: Post-transplant HHV-6 Diseases, Herpes. 2000 Feb, 7(1): p.24-27.
  3. Gabriella Campadelli-Fiume, Prisco Mirandola, and Laura Menotti: Human Herpesvirus 6 An Emerging Pathogen: Emerging Infectious Diseases, Vol. 5, No. 3, May-June 1999, p.353-366.
  4. Ranger S,Patillaud S,Denis F,et al:Seroepidemiology of human herpesvirus-6 in pregnant woman from different parts of the world.J Med Virol 1991 Jul; 34(3): p.194-8.
  5. Asano Y,Yoshikawa T,Suga S,et al:Clinical features of infants with primary human herpesvirus 6 infection(exanthem subitum,roseola infantum). Pediatrics 1994 Jan; 93(1): p.104-8.
  6. Per Ljungman: β-Herpesvirus Challenges in the Transplant Recipient. ; EXTENDING THE BOUNDARIES OF HERPESVIRUS INFECTIONS: ADVANCES IN THERAPY. CYTOMEGALOVIRUS, HHV-6, HHV-7, and Transplantation. ; The Journal of Infectious Diseases. 15 October 2002, 186 (Suppl 1): S99-109.
  7. F.C.Kasolo, E.Mpabalwani and U.A.Gompels; Infection with AIDS-related herpesviruses in human immunodeficiency virus-negative infants and endemic childhood Kaposi's sarcoma in Africa. Journal of General Virology (1997),78,p.847-856.

October 10, 2000 first publication
The April 25, 2006 enlargement
The August 6, 2008 enlargement

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