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Outbreaks of Respiratory Virus Infections

 

In general, patients with respiratory virus infections should be isolated in single cubicles or cohorted with respiratory precautions. The room should be under negative pressure. Gloves and gowns (or plastic aprons) should be worn on entering the room. The value of filter masks is highly debatable, but should be worn when handling the patient. Hand washing must be carried out on leaving the room. The number of staff attending the patient should be restricted. Disinfection of surfaces may be carried out by 1000 ppm hypochlorite. Viruses under this category include varicella-zoster, measles, mumps, rubella, parvovirus, influenza, parainfluenza, and RSV. Where possible, nursing of patients should be carried out by staff known to be immune eg. for VZV, mumps, measles, and rubella. For this reason, It would be invaluable to have a record of staff immunity to childhood illnesses kept either by the sister in charge or by the occupational health department.

1. Chickenpox

Outbreaks of chickenpox is of particular concern in wards with immunocompromized patients, particularly paediatric oncology wards with leukaemic children, adult oncology wards, and bone marrow transplant recipients. It is also of concern in obstetric wards and neonatal wards. In the case of obstetric wards, the main concern is that chickenpox is likely to be more severe in pregnant women, and therefore, if supplies permit, susceptible women should be given ZIG. Any baby born whose mother developed the rash of chickenpox within 7 days of delivery should also be given ZIG and possibly acyclovir. Acyclovir is thought to be safe for the fetus. The following are guidelines for dealing with potential contacts of chickenpox in susceptible wards.

  1. Patients with uncomplicated chickenpox do not require admission to hospital. If admission is required, then the patient should be put in respiratory isolation. The same applies to patients with other conditions who develop chickenpox while in hospital. For patients with shingles, contact isolation would be sufficient.
  2. Other patients on the ward should be assessed for immunity for VZV; usually, a past history of a chickenpox-like illness diagnosed by the General Practitioner is sufficient; however, IgG antibody screening of all patients would be preferable, especially for those individuals who are predisposed to severe chickenpox.
  3. Those found to be negative should be discharged home if their condition allows. If they must remain in hospital, they should be cohorted together and put in respiratory isolation during the period of infectivity (10-21 days following contact), until the incubation period has passed. Essentially, these patients must not have contact with immunosuppressed patients.
  4. ZIG should be given to seronegative patients who are susceptible to severe VZV disease such as leukaemic children, immunocompromised individuals, pregnant women, and neonates. In the latter case, it may also be reasonable to give IV acyclovir since ZIG is not completely effective in preventing neonatal chickenpox, although this has not been properly evaluated. These patients who are given ZIG and isolated should be isolated for at least 28 days since ZIG is known to prolong the incubation period. If ZIG is not available, oral acyclovir may be used instead for a period of 3 weeks. Live vaccine may also be given to children with leukaemia in haematological remission.
  5. Nursing should be carried out by immune staff only. A register of staff immunity is important in view of the susceptibility of 5-10% of the adult population (higher in developing countries). Staff should be assessed for past immunity to VZV, if negative, they should either refrain from work for 21 days (US guidelines), or remain in the same ward, or transferred to other wards with immunocompetent patients doing work which requires less patient contact.
  6. With the availability of the vaccine, it may be advisable to screen all staff in high risk wards and immunized if found to be negative. The problem is whilst this is easy for staff permanently based on the ward, there is also a high turnover of non-permanent staff such as doctors, domestics, porters etc. There is now active discussion on the possibility of screening and administering the vaccine to medical and nursing students. It may be advisable to vaccinate all susceptible leukaemic children who are in haematological remission before admission to hospital.
  7. It may be advisable not to admit non-immune children during the period of the outbreak, up to 3 weeks after the last diagnosed case of chickenpox.

 

2. Measles

Measles outbreaks are most deleterious in wards with immunocompromised children or adults e.g. children with leukaemia and BMT patients. Measles is definitely as dangerous as VZV in that setting. Measles can cause severe disease in babies who are undernourished, immunocompromised, or suffering from chronic debilitating disease. Therefore babies with the above conditions, or who had recently recovered from a severe illness should be protected by HNIG.

  1. Patients with uncomplicated measles do not require admission to hospital, if admission is required, then they should be put in respiratory isolation so that they may be isolated from the immunosuppressed, babies, and non-immune staff and patients. Patients with measles diagnosed in hospital should be sent home where possible if their condition allows.
  2. Nursing should be carried out by immune staff, either in cohorts or in individual rooms during the period of infectivity (4 days preceding to 2 days following the appearance of the rash)
  3. HNIG should be given to all severely immunocompromised children irrespective of their immunization status since it has been reported that severe measles infection can occur in those who had been immunized and had a documented low-level antibody response. Two doses HNIG should be given 48 hours apart, the actual dose depending on the age of the patient. Therefore, the routine screening of children for measles antibody before admission is probably unjustified since there would be no difference in the management. The same argument applies to the screening of patients for immunity before the administration of HNIG.
  4. Immunocompetent children under 12 months in whom there is a particular reason to avoid measles, such as a recent severe illness, or a chronic debilitating disease can also be given immunoglobulin. MMR vaccine should then be given after an interval of at least 3 months, at around the usual age.
  5. The use of live-attenuated vaccine for postexposure prophylaxis is contraindicated in immunocompromised patients. The same protocol applies to immunocompromised adults who come into contact with measles. However, work from Japan suggests that vaccination of leukaemic children in remission is safe and induces a protective immune response.
  6. The live vaccine can be used as postexposure prophylaxis in immunocompetent children and adults who had not been immunized since the incubation period of vaccine measles is 7 days compared with 10 days for clinical measles. All immunocompetent non-immune staff and children in contact with the index case should be vaccinated immediately, within 72 hours, unless a valid contraindication exists. HNIG would be unnecessary in those cases.
  7. Non-immune staff and patients for whom vaccination is too late and who had been a contact with the index case must be regarded as potentially infectious from the 7th day of the first contact to the 14th day of the last contact. During this time, they should be kept away from susceptible patients.
  8. It would be invaluable to have a record of staff immunity to childhood illnesses kept either by the sister in charge or by the occupational health department. Failing a definite medical history, laboratory confirmation may be useful although this service is not normally available from most virology laboratories.

 

3. RSV

Prevention of the nosocomial spread of RSV infection is of prime importance, as many hospitalized infants have underlying conditions which make them susceptible to severe RSV infection. A number of hospital outbreaks of RSV infection have been described in infants, the immunosuppressed, and the elderly.

  1. Affected patients identified clinically as having RSV must be isolated immediately in single cubicle or cohorted for the duration of virus shedding which corresponds to the duration of the symptoms. This period last up to 7 days in healthy children, but can be much longer in the immunosuppressed, leukaemic children, and adults.
  2. Hand washing is the most important measure that can be used in the prevention of infection since the virus is mainly spread by close contact. Gowns and gloves should be worn.
  3. The routine use of gowns and masks has not be shown to be of additional benefit. The use of gowns may be advisable during periods of close contact in which the infant's secretions are apt to contaminate the clothing. Since RSV primarily infects via the eyes and nose, masks are of limited value. Eye-nose goggles have been reported to be of benefit.
  4. Recognition and cleaning of objects contaminated with infant secretions should be carried out as soon as possible.
  5. Infected infants should be isolated and cohorted, preferably as far as possible to infants with underlying chronic diseases who are susceptible to severe RSV infection.
  6. Nursing personnel should be assigned to care for either infected infants or uninfected infants, but not both simultaneously.
  7. During epidemic periods, the numbers of patient contacts and visitors should be limited.
  8. Elective admission of infants with high-risk conditions should be avoided during epidemic periods.
  9. IV RSV immunoglobulin is now licensed by the FDA in the US for the prevention of RSV infection in children < 24 months with bronchopulmonary dysplasia or premature birth (<=35 weeks)

 

4. Influenza

Influenza is a particularly worrying problem in nursing homes where individuals with chronic debilitating disease are especially susceptible to severe life-threatening influenza infection.

  1. Those diagnosed or suspected as having influenza should be cohorted together in one or two rooms, preferably with negative ventilation. The door to the room should be closed.
  2. Hygienic practices among the staff, especially hand washing should be emphasized. Gowns, gloves, and masks are probably unnecessary unless there is prolonged contact with the patient.
  3. Staff taken ill should not report to work
  4. Amantidine prophylaxis should to given to al the other inmates and staff, together with the current vaccine formulation.
  5. Amantidine prophylaxis should be for a period of at least 2 weeks, in order to allow antibody to the vaccine to develop.
  6. Longer period of amantidine prophylaxis, up to 6 weeks or for the duration of the outbreak, should be considered for those who could not tolerate the vaccine due to sensitivity to egg protein, or those who are severely debilitated, since the vaccine is only 70% effective. It is thought that prolonged indiscriminate amantidine usage may lead to the emergence of amantidine-resistant viruses.
  7. Rimantadine may be used in place of amantidine for prophylaxis and the treatment of uncomplicated influenza A infections, although it has fewer neurological symptoms, it is probably not as effective as amantidine.
  8. Zanamivir can be used instead of amantidine for the prophylaxis and treatment of influenza. Being a neuraminidase inhibitor, it has considerably fewer side effects than amantidine and could thus be considered for use in family contacts.

 

5. Rubella

Despite the vaccination program, a small proportion of women of childbearing age is still susceptible to rubella. Therefore, outbreaks of rubella occurring in hospital wards or outpatients affecting susceptible pregnant women is still a possibility.

  1. Affected patients should be sent home or isolated from pregnant women during the infectious period (1 week prior to the appearance of the rash to 10 days after its onset). Babies with congenital rubella should be nursed in standard isolation.
  2. Nursing should be carried out by immune staff.
  3. The immune status of staff and patients on the ward should be determined following the contact. Records of immunity may be available from occupational health or from antenatal clinic records. Where the result was negative or the records were not available, then immune status testing should be carried out. Those who are negative on initial testing should be retested at least 7 days later (or weekly up to 4 weeks) to see whether there is seroconversion together with the appearance of IgM.
  4. Non-immune staff and patients who may be infectious should not have contact with pregnant women during the infectious period (1 week before first contact to 2 weeks after last contact)
  5. In cases where the rubella infection is thought to have occurred some weeks prior to testing or is thought to be reinfection, avidity testing may be carried out.

6. Parvovirus

  1. Infectious patients should be isolated and contact prevented with individuals at risk of aplastic anaemia and pregnant women.
  2. IVIG given periodically can be used for the treatment of aplastic anaemia
  3. In theory, HNIG can also be used for post-exposure prophylaxis although this has not been tested.

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