Moms and dads notice its presence when their children’s cheeks suddenly become reddish. This skin rash is one of the most characteristic symptoms of parvovirus B19, better known as fifth diseasean infection that in healthy children and adults is relatively mild or even asymptomatic, but in some groups of people, such as immunosuppressed people or those suffering from haematological diseases such as sickle cell anemia, and in pregnant women, it can be more serious. After a collapse during the pandemic, experts are reporting a surge: cases are increasing in Europe, and a real boom is being recorded in the US. A focus dedicated to the infectious disease in the scientific journal ‘Jama’ online takes stock.
The data
The numbers collected by the CDC (American Centers for Disease Control and Prevention) give an idea, they are defined as “impressive”: considering all age groups, the share of people with IgM antibodies against parvovirus B19, a sign of recent infection, increased from less than 3% in 2022-2024 to 10% in June 2024. Among children aged 5-9 years, the percentage even jumped from 15% in 2022-2024 to 40% in June 2024. And among the plasma samples collected, the share with a high concentration of parvovirus DNA increased from 1.5% in December 2023 to 19.9% in June 2024.
How it is transmitted
The infection It is mainly transmitted through droplets emitted by coughing or sneezing from an infected person. The growth in cases recorded in the US has prompted the CDC to recently issue a health warning on the matter, also because there is no vaccine or antiviral therapy for the infection.
Given the increase this year, “healthcare providers really need to be on the lookout” for parvovirus B19 infection among high-risk patients, Alfonso Hernandez-Romieu, a medical officer with the CDC’s National Center for Immunization and Respiratory Diseases, warned in Jama Medical News. It’s probably no coincidence, experts say, that parvovirus B19 infections appeared to decline during the early years of the Covid pandemic, when distance learning and social distancing measures introduced to stop SARS-CoV-2 minimized contact among children. In 2018-2019, the highest levels of positive tests, which were among children ages 3 to 5, were 2% to 5%, Hernandez-Romieu noted. In 2021-2022, during the pandemic, rates in that age group have fallen to less than 1%. But parvovirus B19 now appears to be making up for lost time “following the same pattern as so many other pathogens” such as respiratory syncytial virus (RSV), highlights Alasdair Munro, of the UK’s National Institute for Health and Care Research.
Symptoms and contagion
Reduced exposure during the pandemic led to reduced population immunity, allowing for “a remarkable recovery,” Munro said. Despite a significant increase in parvovirus B19 infections locally, the expert said, “we have not noticed any increase in the severity of infections or a change in the nature of complications“, Munro said. For most people, it’s just something that makes them sneeze. According to the CDC, Not all infected people develop symptoms. Among healthy people, those who get sick generally develop symptoms in 2 phases: the first begins about a week after infection and lasts about 5 days, with fever, malaise, muscle pain. And it is in this period of time that parvovirus B19 is most contagious (thanks to higher viral loads and coughing and sneezing).
A week or ten days after this stage, the second begins, when children often develop the bright red rash on the face, which gives it the nickname ‘slapped cheek disease’. By that point, however, when it is clear that it is fifth disease, patients are no longer contagious. The redness on the cheeks may be followed 1 to 4 days later by a rash elsewhere on the body or joint pain. Most people only need treatment to relieve symptoms. In people at risk, the infection can lead to more serious complications, although in a small percentage of cases, because parvovirus B19 infects red blood cell precursors in the bone marrow, which can cause anemia, especially in people who are immunosuppressed or have chronic hemolytic disorders, Hernandez-Romieu notes.
Infection during pregnancy
If pregnant women pass the infection to their fetus, most cases resolve without problems, but complications (fetal anemia or other) can occur in about 5 to 10 percent, according to the CDC. Parvovirus B19 in pregnancy has not been associated with birth defects like Zika and Oropouche infections, says Laura Riley, MD, director of the Department of Obstetrics and Gynecology at Weill Cornell Medicine. It’s also likely that most pregnant women who learn they’ve been exposed to parvovirus B19 don’t get the infection. That’s because there’s some immunity in the population, according to the CDC: By age 40, more than 70 percent of adults have detectable antibodies. “The good news is that many of us had it as children” and will never have it again, Riley says, advising pregnant women who learn they’ve been exposed to parvovirus B19 or have symptoms to tell their doctor, keeping in mind that even if they have the infection and pass the virus on to their fetus, “it doesn’t mean everything is going to be bad,” just that they’ll be monitored.
In conclusion, Hernandez-Romieu suggests, although this infection causes only mild, if any, symptoms in healthy children and adults, physicians should warn high-risk patients about the recent increase in cases and discuss measures to minimize their risk by following established guidelines for the prevention of respiratory viral infections.
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