Mapping long COVID across the EU. Definitions, guidelines and surveillance systems in EU Member States

Background
A health crisis has arisen as an estimated 36 million people in the WHO European region suffer after
a COVID-19 infection from persistent symptoms, termed "Long COVID" or "post-COVID conditions."
Achieving a unified and effective response to Long COVID within the EU is challenging due to the
diverse symptoms related to Long COVID and a lack of a generally accepted definition and diagnosis.
The European Commission underscores the need for a harmonised approach, which has led to the
establishment of the Network of Expertise on Long COVID (NELC) in 2023 to facilitate EU-wide
collaboration. In order to support the work of the NELC, the EUHealthSupport Consortium was tasked
to conduct a rapid mapping study. This mapping study aimes to provide insight into the current state
of affairs regarding: 1) Long COVID definitions, 2) guidelines and intelligence on diagnosis and
treatment, and 3) surveillance systems, as used/implemented EU Member States and beyond.

Methods
A search was conducted to map existing Long COVID and post-COVID definitions, guidelines, and
intelligence on diagnosis, treatment, and surveillance systems in 34 selected countries. Documents
were collected from EU Member States, Iceland, Norway, the United States, Canada, New Zealand,
and Australia. The search encompassed online publications, reports, and guidelines from sources
such as PubMed, national public health institutes, Long COVID primary care and medical specialist
associations, patient associations, and global entities like WHO and OECD. Key search terms such
as 'Long COVID,' 'Long COVID definition,' 'Long COVID treatment,' and others were employed, with
translations into national languages.

Definitions of Long COVID
Long COVID definitions were identified in 33 out of 34 selected countries, with Lithuania being an
exception. Commonly, these definitions align with WHO or National Institute for Health and Care
Excellence (NICE) criteria, distinguishing between duration-based and non-duration-based
definitions. Key elements include time criteria, persistent symptoms, ruling out alternative diagnoses,
and including a broad range of symptoms. Variations exist in considering impact on daily life, organ
system involvement, severity of the initial acute COVID-19 infection, and naming conventions.
Insights from the ORCHESTRA study suggested to define several types of Long COVID, based on
symptom combinations and their impact on physical and mental well-being.

Long COVID guidelines for diagnosis and treatment
The mapping study's second focus was on Long COVID guidelines for diagnosis and treatment.
These were found across 21 out of 34 selected countries. Common elements include advocating a
multidisciplinary approach, a central role for primary care, and the focus on rehabilitation. Some
guidelines include recommendations for referral to specialised care and follow-up procedures.
Guidelines differ in their target audience, addressing healthcare providers in general, secondary
(specialised) care, decision makers, and interdisciplinary support involving municipalities. Guidelines
also differ to some extent in addressing specific symptoms or organ systems that are affected by
Long COVID. A quick literature search indicates that additional guidelines are still under development
for various specific medical specialties and possible ways of treatment.

Long COVID surveillance
The third focus of the study was the mapping of Long COVID surveillance systems, initially using the
search term 'surveillance system', with no result, and later 'registry.' Seven Long COVID registries
were found in Australia, Germany, Spain, Sweden, the Netherlands, New Zealand, and the United
States. In addition two additional registries, one from Germany and one from Czechia, were added
after a review round among the NELC Members. Five of the mentioned Long COVID registries are
based on self-registration. The Spanish registry involves primary care professionals in recruitment
and the Swedish registry is based on registration data. The Australian registry uniquely allows carers
to register as well. Data linkage to other sources is specified only in the New Zealand registry.
Notably, except for the Swedish and one of the German registries, none of the registry websites
provide insights gained or expected timelines for results. As limited information is available for most
registries, a detailed understanding of their structures and goals in comparison to others is hindered.
Some countries, including Bulgaria, Italy, Germany, and Ireland, have implemented clinical centers
for Long COVID patients from which data can be collected that may serve as an alternative source
of information on the Long COVID population. Similarly, several countries have implemented or are
implementing cohort studies for Long COVID patients.

Reflections and conclusion
This rapid mapping study underlines the interconnectedness of Long COVID definitions, the
development of guidelines, and surveillance systems. A clear definition is crucial for developing
effective guidelines and surveillance, but defining Long COVID is still challenging due to the broad
range of symptoms involved. The ORCHESTRA project's multi-type definition may enhance refined
guidelines and surveillance. It can be concluded that in most EU Member States guidelines for the
diagnosis and treatment of Long COVID need to be developed or need to be made publicly available.
Member States in which guidelines are available could serve as an example.
Given the variability in definitions and the voluntary entry of patients into the existing registries, there
are no good estimates yet of the total numbers of patients and the severity of their disease in EU
Member States. Linking information from cohort studies and clinical trials may be necessary to
provide the full picture of the burden of disease of Long COVID.