A new study conducted by KSM, the Research and Innovation Center of Israel’s Maccabi Health Services, indicates that Israel is experiencing an unprecedented outbreak of parvovirus B19.
The virus causes erythema infectiosum, commonly known as “fifth disease” or “slapped face disease” because of the bright red rash it causes on a child’s cheeks.
Spread via respiratory droplets, fifth disease is a common childhood illness. Aside from the rash, the virus usually causes flu-like symptoms and sometimes also joint swelling and pain. Around 20 percent of children with the virus do not have any symptoms, but are contagious and can infect others.
Fifth disease is usually mild in children, who overcome it in a week to 10 days with little or no treatment. Infected adults tend to exhibit flu-like symptoms, but do not have the rash. However, the virus can cause complications in immunocompromised individuals and can be damaging to fetuses in early pregnancy.
The peer-reviewed study found that 2023 experienced the largest and longest reported spike in parvovirus in Israel.
KSM mined the data of Maccabi’s 2.7 million members from January 2015 to September 2023 and found that in 2023 there was a six-fold risk for parvovirus infections over the previous years. The risk was nine-fold in 2023 compared to the COVID-19 years (2020-2022).
“Maccabi’s members are 25% of the population. This is a huge sample, so these statistics are reflective of the situation in the entire population,” KSM head Dr. Tal Patalon told The Times of Israel.
Maccabi’s data shows that among its members, there were more than 9,000 parvovirus infections since 2015, with 40% of them in 2023. This translates to at least between 14,000 and 15,000 infections among all Israelis this year alone.
The study found that there was no seasonality to parvovirus infections in 2023. This is highly unusual, as infections are usually seen in late winter and spring — and not throughout the year as occurred this year.
According to Patalon, KSM decided to look into parvovirus when doctors started anecdotally reporting that they were seeing more patients, including pregnant women, sick with it than usual.
“The way we research at KSM is called ‘small big data.’ We start with doctors working in the field with patients and coming to us with observations. From there, we go back to the big data of the whole organization, and we follow this lead,” Patalon explained.
“That’s how we can catch an early change in trajectory in any disease. It’s a matter of connecting the dots between the anecdotal reports and the data. And if we find a spike, we need to start looking at it,” she said.
At this point, the reason for this unprecedented outbreak is unclear. One theory would be that with Israelis isolating for long periods between 2020 and 2022, the transmission of the virus was suppressed until 2023 when people were able to interact more freely and without masks.
“It could be that something has happened with the virus. That needs to be investigated. Sequencing viruses is the job of the Health Ministry, which is aware of the spike in infections,” Patalon said.
In the meantime, KSM is researching the outcomes of women and children who got the virus.
Patalon stressed that the point of sharing the study’s findings widely is not to sow panic among the public. Rather, it is to encourage physicians and other health professionals to be more aware of the situation and to check for the virus when they see patients presenting with symptoms. The diagnosis can be done through a serology blood test.
According to the medical literature, only half of women have been exposed to parvovirus as children. Therefore, they should be careful not to be exposed to someone infected with parvovirus, especially while in their first and second trimesters.
“But again, we don’t want to cause hysteria and add to the stress and anxiety of pregnant women. Only 10% of pregnancies will experience a complication from the virus, and of those, very few will experience fetal loss,” Patalon said.