The disease caused by SARS-CoV-2, COVID-19, has been with us for more than two years and has infected more than 470 million people, leaving more than six million deaths in its wake. Although in most cases the symptoms disappear in the first few weeks, there is a percentage of people who may experience symptoms several months after being infected by the virus and is known as persistent COVID.
What is persistent COVID-19?
In simple terms, persistent COVID-19 is defined as the presence of at least one symptom caused by SARS-CoV-2 infection after 30 days of illness onset. However, this new study proposes using 90 or 120 days after infection as the most representative parameters.
The scientific community first identified in August 2020 that around 87% of COVID-19 patients continued to present at least one symptom up to 60 days after the onset of the disease. Subsequent studies revealed that geographic region, gender, age, and sociodemographic characteristics are factors that condition the appearance of persistent COVID.
43% of those infected develop persistent COVID
A study recently accepted for publication has analyzed almost 4,500 international studies written in English, of which 50 were included and 41 were evaluated in detail. Presence of persistent COVID was defined as symptoms 28 days or more after infection.
The analysis determined the prevalence of persistent COVID to be approximately 43% of infected, with nearly 1.7 million individuals included from around the world. This new data is much lower than that reported in the first months of the pandemic (more than 80% based on various studies).
However, this percentage did not remain the same among all infected people. A difference was observed between those infected who had to be hospitalized, where the prevalence rises to 54% compared to 34% in non-hospitalized patients .
They have also shown that this prevalence varies by region. In Asia, a prevalence of 51% of infected people is observed , while in Europe it is 44% and 31% in North America . The number of factors involved, from the availability of diagnostic tests, vaccines or access to healthcare, is so extensive that it is difficult to identify the most relevant.
What symptoms are more frequent in persistent COVID?
In the case of suffering from a SARS-CoV-2 infection, there are a series of symptoms that are more frequent than others. This is also true in the case of persistent COVID. This study has determined that the most frequent symptom among these people was fatigue, present in 23% of cases .
The second most frequent symptom turned out to be problems associated with memory, with a 14% prevalence , followed by dyspnea (respiratory difficulty or shortness of breath) with 13%, sleep problems with 11% and joint pain with 10%. A total of 23 symptoms were reported, the rest with prevalences below 10%.
Female gender and asthma as risk factors
Two of the factors that proved to be most relevant in the frequency of persistent COVID turned out to be female gender and the presence of asthma prior to the disease . Apart from the analysis applied by these researchers, other factors such as age, obesity or hypothyroidism also seem to be risk factors.
On the other hand, the possibility that there are protective factors that do not appear in this study is mentioned. This absence may be due to the limitations in the included studies, especially when considering the beginning of the pandemic when there was no widespread testing routine in the population.
Another important factor to take into account is the most frequent type of symptoms for the different variants . In the case of the Omicron variant, mild symptoms are more likely to be found compared to the Delta variant. However, this variant has been studied in a largely vaccinated population in Europe and may be a determining factor.
One of the studies analyzed showed that vaccines can also have a protective effect against persistent COVID, although another large study suggests just the opposite effect. Although the effect of vaccines in preventing severe symptoms, hospitalization, and deaths is clear, more studies are needed to determine their effect in preventing persistent COVID .
How does persistent COVID affect society?
Taking into account the infection rate that SARS-CoV-2 has caused globally, no matter how minimal the prevalence of persistent COVID is, it can account for a large percentage of the world population . This percentage of those infected, who may present symptoms up to several months after the onset of the disease, can have a great impact on society and the economy .
It is evident that more studies on the prevalence, consequence and treatment of persistent COVID are necessary, especially in the context of vaccinated populations. If we are forced to live with waves of coronavirus infections, it is essential to reduce the prevalence of this persistent infection that affects almost half of those infected .
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References:
Chen et al. 2022. Global Prevalence of Post COVID-19 Condition or Long COVID: A Meta-Analysis and Systematic Review. J Infect Dis. doi: 10.1093/infdis/jiac136.
