The current surge in respiratory syncytial virus (RSV) cases in Sweden has already strained the capacity of at least one pediatric ward in the country, local media reported.

"We are in the middle of a steep rise, a wave that has come earlier than it usually does," AnnaSara Carnahan, an epidemiologist at the Public Health Agency of Sweden, told Dagens Nyheter (DN) newspaper on December 8.

The surge surprised the health authorities, who now see an unprecedented spike in the number of cases for the second winter in a row, Xinhua news agency reported.

"When there is no (COVID-19) pandemic, we usually have an every-two-years pattern, with a major epidemic one winter, followed by a slightly milder season. This pattern was disrupted during the (COVID-19) pandemic," Carnahan told DN.

An RSV infection often causes the same symptoms as a common cold, but Carnahan said that it predominantly affects young children.

"For the smallest children who have not previously been infected, it can be difficult, especially due to the sticky mucus that can make it hard for children with tiny airways to eat and breathe," she added.

The epidemic is sending infected children to emergency wards and pediatric hospitals in higher numbers than normal, DN reported.

RSV spreads mainly among young children. Most children by the age of two develop antibodies to the virus after becoming infected. However, the antibodies do not provide permanent immunity. Severe respiratory symptoms may require treatment with oxygen, and in some cases ventilator treatment, according to the Swedish Publish Health Agency.