June 10, 1998
Information on Enteroviruses for Doctors
Enteroviruses including polioviruses, coxsackie viruses, echoviruses are small RNA viruses. Enterovirus 71 (EV-71) is one type of enteroviruses and it has been isolated from children in Taiwan suffering from hand, foot and mouth disease recently.
Epidemiology
Enterovirus infections occur worldwide and asymptomatic infections are common. There is seasonal trend with most cases occurring in summer months.
The mode of transmission is predominantly the faecal-oral route but the enteroviruses can also be spread through droplets or direct contact with respiratory secretions. Humans are the natural host for enteroviruses with children, in particular those below the age of 5, being most affected during outbreaks. Infection is most common under conditions of poor hygiene and overcrowding, e.g. institutions.
The incubation period for enterovirus diseases is usually between 1 to 2 weeks. Viruses may be shed from the oropharynx from 2-3 days before to 1-2 weeks after onset of symptoms, and in faeces for several weeks to months.
Clinical Diseases
Although enteroviruses can cause a number of clinical diseases affecting the neurological, cardiovascular and respiratory systems, the majority of enterovirus infection in children are asymptomatic. Enteroviruses are important causes of aseptic meningitis and enchephalitis, neonatal sepsis, and acute febrile illnesses in children. They are also capable of causing paralysis and acute motor weakness. Enteroviruses are well known to cause pericarditis, myocarditis, stomatitis, hand, foot and mouth disease, haemorrhagic conjunctivitis etc.
Diagnosis and Treatment
Hand, foot and mouth disease is normally diagnosed clinically. For definitive diagnosis of enterovirus infections e.g. enterovirus 71 infection, isolation of the virus from cell culture should be attempted. Specimens for virus isolation include nasopharyngeal swabs, cerebrospinal fluids, rectal swabs, stool samples etc.
There is currently no effective antiviral therapy for acute enterovirus infections. Supportive care is the mainstay of treatment. Apart from polioviruses, there are no vaccines against enteroviruses.
Situation in Taiwan
According to the Department of Health of Taiwan, their surveillance system has detected an upsurge of hand, foot and mouth disease in children since end April 1998. Virological culture from hospital cases yield coxsackie virus and enterovirus 71. Actions are being carried out to trace the source of infection and contain the spread of the illness. Up-to-date information can be obtained from their homepage at http://www.dsqs.gov.tw (please go to the Disease Investigation and Surveillance Communications (DISC) ).
Situation in Hong Kong
In Hong Kong, Department of Health's Government Virus Unit regularly diagnoses enterovirus infection from specimens sent by hospitals and clinics. Owing to the increased surveillance for influenza since the H5N1 incident in 1997, the number of specimens received by Government Virus Unit in 1998 has greatly increased and it explains for the higher number of enterovirus infections detected. According to hospital clinicians and the primary care doctors in both public and private sectors, there is no unusual rise in enterovirus activity like hand, foot and mouth disease.
Enterovirus Infections in Hong Kong 1994-98
| Year | Coxsackie | Enterovirus 71 | Other enterovirus | Total |
| 1994 | 111 | 0 | 22 | 133 |
| 1995 | 36 | 1 | 34 | 71 |
| 1996 | 49 | 0 | 21 | 70 |
| 1997 | 30 | 2 | 32 | 64 |
| 1998 (Jan-May) | 16 | 0 | 51 | 67 |
The situation is being monitored closely. The sentinel surveillance system in both public and private sectors is being set up for hand, foot and mouth disease.
Advice to Doctors
Enterovirus infection can be prevented by observing strict personal hygiene. Children suffering from the infection should be advised to stay at home and avoid contacting other children until the illness is over. Strict handwashing after handling excreta like stool, repiratory secretions etc is important. The public are advised to increase their body resistance through adequate rest, regular exercise, balanced diet, reducing stress and no smoking. The importance of maintaining good ventilation and avoidance of going to overcrowded places should be stressed.
Although myocarditis is a common complication of enterovirus infection, it has been observed in recent outbreaks, in particular with the enterovirus 71 infection, that neurological complications like brain stem encephalomyelitis are more readily observed. The brain stem pathology could also be revealed by MRI studies.
Please inform the Department of Health promptly (Tel. 2961 8918 , Fax 2836 0071) if you see an unusually large number of cases of hand, foot and mouth disease or the cases are of great severity e.g. older age group, large number of vesicles or body parts affected, rapid deterioration of clinical condition, involvement of neurological system etc.
Department of Health