Parvovirus B19 is a member of the parvoviridae family of single-stranded DNA viruses and is one of the smallest viruses known to infect human cells. The virus is usually transmitted by droplet spread through respiratory secretions. More rarely, parvovirus B19 is transmitted across the placenta in a pregnant woman, or by blood transfusion. The incubation period is around 14–21 days.¹ Parvovirus B19 infection can cause ‘slapped cheek syndrome’ (also known as erythema infectiosum or fifth disease), most commonly in school-age children. It is usually a mild, self-limiting illness, which is followed by lifelong immunity. 

Parvovirus B19 infection is not a notifiable disease in Ireland. It is therefore difficult to determine prevalence in Ireland as this data is not collected. One study monitored prevalence in three regional hospitals in Ireland over a 12-year period and noted 546 positive tests for parvovirus out of 12,430 samples. Most cases occurred between March and July, indicating a seasonal trend.²

Complications and prognosis

Complications of B19 infection are rare in healthy children and adults. In children, a rash affecting the trunk and limbs may recur months after the acute infection, following exposure to sunlight, heat, stress, or exercise. In adults, joint pain may persist for months after the acute infection, or may recur several months after the acute infection. Pregnant women, and people who are immunocompromised, or those who have haematological disorders are at increased risk of serious and potentially life-threatening complications. Serious complications include severe anaemia, encephalitis and myocarditis.³

In pregnancy, parvovirus B19 infection can cause serious complications for the foetus, including foetal death in approximately 5-10% of cases. Foetal loss usually occurs in the second trimester. The prognosis partially depends on the gestational age at infection. The risk of transmission to the foetus is increased between nine to 20 weeks’ gestation. The foetus is most vulnerable if it is infected in the second trimester, with the peak risk occurring at 17–24 weeks’ gestation. At less than 20 weeks’ gestation, the estimated excess foetal loss rate during pregnancy is about 9%. Transplacental transmission of parvovirus occurs in about 30% of women depending on gestation, with an average of about six weeks between maternal infection and foetal symptoms.⁴

Diagnosis

In healthy children, the diagnosis of parvovirus B19 infection is usually made on clinical grounds. Parvovirus B19 infection should be suspected if a child presents with a characteristic facial rash, appearing on one or both cheeks, resembling a ‘slapped cheek’. The rash may be preceded by two to five days of symptoms such as low-grade fever, nasal discharge, headache, muscle aches, and mild nausea and/or diarrhoea. The facial rash usually fades after one to two weeks and is often associated with a paleness around the eyes or mouth.^1,4

A rash may develop on the trunk, back and limbs a few days after the facial rash, which fades to produce a lace-like rash. This usually resolves over a few days or weeks. There may be associated itching, for example of the soles of the feet. Rarely, there may be associated inflammation of the knee and ankle joints.^1,4

In healthy adults, it is difficult to make a diagnosis of parvovirus B19 infection on clinical grounds as symptoms may be atypical and may mimic other conditions. Around 25–50% of adults are asymptomatic. Suspect infection in adults if they present with a history of contact with parvovirus B19 infection (usually in a child), or if there is a known local outbreak. The infectivity period is seven to 10 days before a rash develops to the day after the onset of rash. Symptoms such as mild fever, malaise, myalgia, and headache may appear about a week after contact with the infection and before the appearance of the rash.^1,4

The characteristic facial rash seen in children is rare in adults, but two to three weeks after the first symptoms, a rash may develop on the trunk, back and limbs, which fades to produce a lace-like rash. This usually resolves within a week. There may be joint inflammation following the appearance of the rash, which is more common in women and typically affects the hands, and less commonly the wrists, knees, and ankles. The joints may be painful, swollen, and stiff. Joint symptoms usually last for between one to three weeks, but may rarely persist for months or years.^1,4

Other conditions that may present similarly to parvovirus B19 infection include rubella, measles and scarlet fever etc.

Investigation and management

In healthy children and adults, the diagnosis should be based on clinical features. Laboratory investigation to confirm the diagnosis is not required.⁶

If a pregnant woman has suspected parvovirus B19 infection, or possible exposure to parvovirus infection, contact the local virology, microbiology or infectious diseases department immediately for further advice. Urgent blood testing is likely to be advised. 

If parvovirus B19 infection is suspected in a person who is immunocompromised or has a haematological disorder, urgent blood testing should be arranged.¹

For children and adults (who are not pregnant) with suspected parvovirus B19 infection, the date of onset of symptoms should be recorded along with the clinical features and type and distribution of any rash and associated illness. Previous relevant history of infection, contact with any person with a potentially infectious rash or illness (with dates of contact), antibody testing and vaccine administration (with dates/places) should be taken. For people who are at risk of complications, laboratory investigations should be organised and appropriate follow-up, referral or admission undertaken arranged.^1,2,6 

For healthy children who have the typical rash of slapped cheek syndrome, advice should be given that the child should no longer be infectious once the rash develops and it is not necessary for the child to stay off school or nursery. It is not necessary to avoid contact with pregnant women. Schools or nurseries should be informed of the child’s suspected parvovirus B19 infection so that people at risk of complications can be informed that the virus may be circulating.^1,2,6

For healthy adults with suspected parvovirus B19 infection, advice should be given that it is not usually necessary to stay off work if symptoms are controlled. It may be sensible for healthy adults to avoid contact with pregnant women while any rash is present, until the person’s rubella status is known.^1,2,6

Potential exposure 

Children and adults (who are not pregnant) who have had possible exposure to parvovirus B19 infection but have not yet had symptoms should avoid contact with pregnant women and people who are immunocompromised or have a haematological disorder, until they are no longer potentially infectious. The infectious period is seven to 10 days before the rash (if any) develops, until one day after the rash appears.^1,5

Significant contact is defined as being in the same room for 15 minutes or more, or face-to-face contact with the person, within the previous three weeks. Be aware that the greatest risk comes from any children in the person’s household, rather than the workplace.¹ If there is any uncertainty on the requirements for isolation from at-risk people, contact the local virology, microbiology or infectious diseases department for further specialist advice. 

Management in pregnancy

If parvovirus B19 infection is suspected at any stage of pregnancy, be aware that the clinical features may be indistinguishable from rubella infection. The woman’s gestation of pregnancy and expected date of delivery should be recorded along with the date of onset of symptoms, clinical features, and type and distribution of any rash and associated illness. Previous relevant history of infection, immunoglobulin G (IgG) antibody testing and measles/rubella vaccination status (with dates/places) should be noted. Ask about any known contact with any person with a potentially infectious rash or illness and dates of contact. Contact the local virology, microbiology, or infectious diseases department immediately for further advice on laboratory investigations and monitoring.^1,4,5,6 

Give advice on self-management strategies for symptom relief. Advise the woman that it is not usually necessary to stay off work if symptoms are controlled. 

If the woman has not been fully immunised against rubella or does not have a documented history of previous rubella infection, it may be sensible to avoid contact with other pregnant women while any rash is present, until her rubella status is known.

If parvovirus B19 infection is confirmed in a pregnant woman urgent referral to a specialist in foetal medicine should be arranged. Advise the woman that transmission to the foetus is unlikely and specialist foetal monitoring will be arranged. If foetal transmission occurs, there may be effective specialist treatment options available. If there are any suspected acute complications the woman should be admitted to hospital.^1,4,5,6

Potential exposure

If a pregnant woman reports possible exposure to parvovirus B19 infection at any stage of pregnancy without symptoms blood tests should be arranged as soon as possible after contact and the woman should be advised to avoid contact with other pregnant women and people at risk of complications until she is known to be uninfected,immune to infection, or no longer potentially infectious.^4,6

References

1. PHE. Parvovirus B19: guidance, data and analysis. Published 2012. Available from: https://www.gov.uk/guidance/parvovirus-b19 [Accessed May 3, 2017]. 
2. Nicolay N. and Cotter S. (2009) Clinical and epidemiological aspects of parvovirus B19 infections in Ireland, January 1996 - June 2008. Eurosurveillance. 14(25): 19249. Available from: http://www.eurosurveillance.org/ViewArticle.aspx?ArticleId=19249
3. O’Grady J. (2014) Fifth and sixth diseases: More than a fever and a rash. Journal of Family Practice. 63(10): E1-E5. Available from: http://www.mdedge.com/jfponline/article/87594/pediatrics/fifth-and-sixth-diseases-more-fever-and-rash [Accessed May 3, 2017].
4. SOGC. Parvovirus B19 infection in pregnancy. SOGC Practice Guideline. Published 2014. Available from: https://sogc.org/wp-content/uploads/2014/12/gui3161012E.pdf [Accessed May 3, 2017].
5. Slavov S.N., Kashima S., Pinto A.C., and Covas D.T. (2011) Human parvovirus B19: general considerations and impact on patients with sickle-cell disease and thalassemia and on blood transfusions. FEMS Immunology and Medical Microbiology. 62(3): 247-262.
6. UK National Screening Committee. Parvovirus B19 infection in pregnancy. A brief review of the literature. Published 2014. Available from: https://legacyscreening.phe.org.uk/policydb_download.php?doc=444 [Accessed May 3, 2017]