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Outbreaks of Enteric Viral Infections

 

1. Diarrhoeal Viruses

Most admissions from the community for viral diarrhoea, other than in a food-related outbreak, occur in winter usually in children under 3 years old. Rotavirus account for over 50% of episodes of acute viral diarrhoea in children.

  1. Standard "enteric precautions" or otherwise known as "faecal-oral" isolation is required for patients with viral diarrhoea. Cohort nursing is acceptable as long as no patients are admitted to the cohort unless infection is proven.
  2. In infants and children, shedding of rotavirus, adenovirus, and astrovirus continues for many days following resolution of the symptoms and therefore they should continued to be isolated for 5 days after the symptoms have cleared.
  3. In adults, less virus is shed once the acute episode has passed. Therefore, they do not need to be isolated once their symptoms have cleared.
  4. Nursing personnel should be assigned to care for either infected infants or uninfected infants, but not both simultaneously.
  5. Eradication of rotavirus from a long-stay geriatric ward or neonatal unit may be impossible partly as a result of recolonization of the ward by chronic carriers such that even closure and cleaning are ineffective

2. Polio

Since the advent of polio vaccination, the majority of reported cases of paralytic poliomyelitis were due to vaccine strain virus. However, cases of paralytic poliomyelitis are still reported from time to time.

  1. The polio isolate should be examined further to determine whether it is vaccine or wild type. Initial testing may include the RCT 40 testing. Reference testing may involve the use of monoclonal antibodies and/or sequence analysis.
  2. Detailed history should be obtained; such as vaccination history, contact with any persons who may have been vaccinated recently
  3. The patient should be isolated with enteric precautions, preferably contact isolation, since high-dependency nursing will probably be required, and also that polio may be transmitted through nasopharyngeal secretions
  4. If wild virus is confirmed, then a single dose of OPV should be given to all persons in the immediate neighborhood of the case, regardless of a previous history of immunization against poliomyelitis. Individuals with genuine contraindications such as immunodeficiency should be given IPV. In previously unimmunized individuals, the 3-dose course must be completed.
  5. If there is laboratory confirmation that a vaccine-derived polio virus is responsible for the case, immunization of further possible contacts is unnecessary since no outbreaks associated with vaccine virus have been reported to date. If the source of the outbreaks uncertain, it should be assumed to be a "wild" virus and appropriate measures instituted.

 

3. Coxsackie and Echoviruses

In normal wards, enteric precautions would be sufficient after the diagnosis of a coxsackie or echovirus infection, paying particular attention to hand washing, disinfection of surfaces with hypochlorite 1000 ppm, heat disinfection of bedpans and instruments. However, coxsackie or echoviruses may cause severe problems in a neonatal ward.

  1. Pregnant women with a flu-like illness a few days before delivery should be isolated with enteric precautions.
  2. She should be investigated for enterovirus infection e.g. throats swabs, stools, and possibly blood for serological tests
  3. Her baby should be put in contact isolation after birth, and given HNIG or IVIG if born within 7 days of maternal symptoms.
  4. The baby should be examined for enterovirus infection
  5. Other babies in the neonatal wards should be given HNIG or IVIG if supplies permit. (In fact, it is now routine to give all premature babies weekly IVIG, IVIG is probably preferable in babies because of the ease of administration once an IV line is in place.)

 

4. Hepatitis A

  1. Standard precautions should apply to patients with hepatitis A. It may be advisable to put patients with a poor standard of hygiene in a side room.
  2. Staff constantly exposed to patients with hepatitis A should be advised to be tested for immunity and vaccinated if non-immune.
  3. By the time jaundice appears, hepatitis A excretion is probably well past its peak and may even be undetectable. Therefore, HNIG would not be of any use in these circumstances.
  4. However, postexposure prophylaxis may be considered in schools and institutions where personal hygiene may be poor.
  5. Hepatitis A vaccine may be given at the same time but its efficacy in postexposure prophylaxis is uncertain at present
  6. During an outbreak in an institution, good hygiene practices such as hand washing should be practiced.

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