Parvovirus and Slapped Cheek syndrome

‘Slapped cheek’, or erythemaa infectiosum, is the most common clinical presentation of parvovirus B19.

Background

• Parvovirus is the smallest virus known to infect mammals.  The only pathogenic type is the B19 strain.
  • Transmission is usually via respiratory droplets but can also be transmitted via blood-blood contact.
  • Incubation is 4-20 days prior to symptom development and the individual is infective from 10 days before the rash until its onset (no longer infectious once symptomatic).  Infectivity is around 50%.
    • Most people have contracted the virus unknowingly and are immune by adulthood.
• Most commonly presents in children aged 3-15 years, and is seasonal (more commonly seen in late spring/early summer)

Presentation

• Most commonly, erythema infectiousum (fifth disease)
  • bright red rash, commonly on the cheeks but can on the trunk too
  • often accompanied by a paleness around the mouth (circumoral pallor)
    • Some children will develop a second stage rash a few days later: erythematous maculopapular rash of trunk and limbs which fades to a lacy rash
      • this can be itchy in older children/adults
    • Rarely, parvovirus infection can present with other rashes (vesicopustular or purpuric rashes; koplik spots) and itching on the palms/soles may be the predominant feature
• Can be preceded by 2-5 days of prodromal sickness
  • fever, coryza, headache, nausea, diarrhoea
• Infection can also cause arthropathy, most commonly in the PIP and MCP joints (symmetrical polyarthropathy).
  • Rare in children, more common in adults

NB Particularly in adults, parvovirus infection can be indistinguishable from rubella (in kids, the facial rash is almost diagnostic).

Special cases and complications of parvovirus infection

1. Haematological conditions that reduce RBC count (e.g. sickle cell anaemia; thalassaemia; hereditary spherocytosis; iron-deficiency anaemia) as well as other blood abnormalities (e.g. thrombocytopenia, neutropenia)
   1. A transient aplastic crisis (decreased amount of reticulocytes, such that the RBC count drops dangerously low) can occur with infection.  Some of these patients will require blood transfusions.  These patients are also highly infective.
2. Immunocomprimised patients
   1. May not be able to fight infection and can remain infectious.  They may also test negative using IgM tests (they can’t produce the IgM).  Severe cases can develop a viral meningoencephalitis.
3. Pregnancy
   1. Parvovirus can cause complications in pregnancy and increases the chance of foetal loss by 5-10%.  It can cause hydrops fetalis, foetal anaemia, hepatitis, myocarditis and heart failure.
      1. More serious earlier in pregnancy.
   2. All pregnant women who have a non-vesicular rash, or contact (>15 mins in a room or face-face contact) with someone with a rash, should be tested (IgM test for acute infection and IgG for immunity)
      1. If IgM +ve/IgG -ve, immediately do a repeat test for confirmation.  If IgG +ve/ IgM -ve, patient can be reassured.  If both -ve, patient should be tested one month later (if again negative, patient can be reassured)
      2. Further tests of viral DNA should be done if IgM is repeatedly elevated to confirm active infection.
   3. If confirmed infection, the mother should be more closely monitored with scans for hydrops fetalis and may require foetal blood sampling and intrauterine infusions.  Early delivery may be warranted.

Investigations

• Investigations (see above) are only required in special cases (as above) or if there is persistent arthropathy

Management

• Uncomplicated disease is self-limiting and requires no treatment.  Patients don’t need to take time off school/work.  Symptoms should resolve after a few weeks.
• If there are complications in special cases, these may require admission and active treatment of complications (no antivirals are required)
• Advise to avoid contact with pregnant women/immunocompromised individuals etc.