Outbreak of parvovirus B19 disease in France: urgent need in public health for relevant tools to track epidemics in real-time

SUMMARY.

• France and many European countries have been experiencing a significant outbreak of the parvovirus B19 infection for several months.

• The first reports from the health authorities about this epidemic in France were very late, highlighting the weaknesses in our surveillance system.

• This commentary calls for concerted action by public health authorities to swiftly improve the current infectious disease surveillance network at both national and European levels.

Parvovirus B19 (B19) infection is a highly contagious disease transmitted primarily through the respiratory route. Also known as fifth disease (erythema infectiosum), it is a mild illness that predominantly affects children aged between 4 years and 10 years old. In immunocompetent adults, B19 infection is often associated with a polyarthropathy syndrome that can last for weeks or months.

However, B19 can also cause severe infection, especially in immunocompromised individuals and those with an underlying haemolytic disorder. These patients, particularly organ transplant recipients, can harbour high and persistent respiratory viral loads, making them potential sources of secondary infections such as nosocomial infections or infections transmitted to healthcare staff. Additionally, B19 primoinfection during the first 20 weeks of pregnancy can lead to severe outcomes such as miscarriage or fetal death.

At the end of 2023, we witnessed an unusually high incidence of B19 infection cases affecting both children and adults, followed by increased maternal-fetal infections (figure 1) in our hospital centre laboratory. Locally and among clinicians, only obstetricians dealing with fetal pathologies had any idea about this development.

Figure 1. Monthly prevalence of Parvovirus B19 IgM antibodies (blue curve) and monthly incidence of Parvovirus B19 fetal infection (orange histogram) from January 2020 to May 2024 at Toulouse University Hospital Centre.

At that time, neither national nor international official alerts from the public health authorities regarding a potential B19 outbreak were available despite two publications from France and Israel.^{1 2}

More recently, the upsurge in B19 detection in five European countries was described in the European Centre for Disease Prevention and Control (ECDC) weekly bulletin,³ and the French Ministry of Health issued an alert in late April 2024,⁴ almost a year after the outbreak began in France. Since then, a number of recent publications have reported on this epidemic in France and other European countries.⁵,⁸

The prevention of transmissible infectious diseases is a major public health issue and lies at the forefront of concerns of national and supranational healthcare actors.

In France, several surveillance systems for transmissible infectious diseases coexist and are coordinated by the public health authorities at different levels (regional and national): from mandatory reporting, quickly transmitted to national level by regional health authorities to syndromic reporting networks established by emergency departments or voluntary general practices. Finally, National Reference Centres for infectious diseases can collect incidence data and forward alerts to the health authorities. National data may be sent to the ECDC for supranational surveillance.

These multiple notification methods overlap and appear to be effective. Indeed, some diseases such as arboviroses and measles are in the spotlight, but the current reporting system neglects other transmissible infectious diseases of medical interest that can slip under the radar for varying lengths of time. Some infectious diseases are excluded from this French surveillance system; this includes B19 infection, which is neither a reportable disease nor one for which a reference centre exists in France.

A surveillance system for B19 is currently lacking in other European countries such as Denmark which reported an epidemic lasting from January to March 2024.⁸

In the post-COVID-19 pandemic era and within the context of the One Health initiative, it is essential to have an efficient and rapid (ie, automated) reporting system in place to respond to the spread of infectious diseases. French health authorities were aware of the importance of monitoring infectious diseases and the risk they pose, especially in the context of the Paris Olympic and Paralympic Games. Such events, which bring together many people from around the world, have previously been linked to epidemic phenomena such as the 2014 Zika outbreak in Brazil.⁹ French health authorities are considering an automated reporting system,¹⁰ but this has proved too complex for speedy and nationwide implementation and remains incomplete, covering only a few diseases.

A practical and easy solution, which could be applied by all diagnostic laboratories with significant infectious disease diagnostic activity, would consist of automated and standardised real-time analysis of data from laboratory computer systems. The data analysed would be selected according to their clinical relevance; for example, IgM and viral DNA or even a recent IgG seroconversion in the case of acute B19 infection. Relevant variations in incidence rates could be used to trigger alerts, expertly validated by the laboratories and then swiftly transmitted to the public health authorities. This should be all the quicker to implement as health regional agencies already have available access to emergency contacts, with medical staff on call. These public health authorities would then handle the downstream flow of information. This is essential to ensure that field staff are promptly informed about the onset and development of an epidemic in order to better prevent, diagnose and manage patients at risk.

To conclude, there is an urgent need to improve and standardise the current surveillance network for infectious diseases at both national and European levels. This is especially critical in the context of mass gatherings such as those taking place during the Paris 2024 Olympic and Paralympic Games. The rapid centralisation of pertinent and exhaustive information through simple tools, followed by its redistribution to the field, remains a paramount goal to achieve. This will create a virtuous circle that forms the basis of better patient care, both through the establishment of individual or collective protective measures and the prescription of appropriate therapeutics.

Data availability statement

Data are available upon request.