Influenza B cases increase significantly in latest monitoring: CNIC

The proportion of influenza B cases has seen a substantial increase among influenza patients across the country while the previously dominant influenza A (H3N2) has seen a significant decrease in proportion, the latest monitoring report released by the Chinese National Influenza Center (CNIC) shows.

According to the Influenza Weekly Report released by CNIC last Thursday, between December 25 and 31, 2023, the proportion of influenza B virus strains currently account for 26.4 percent of the influenza cases in the southern parts of China and as much as 47.3 percent of the influenza cases in the northern parts of the country.

Despite that the influenza A (H3N2) virus strains are still prevalent and account for 63.8 percent of the total influenza cases detected across the country, their dominance in transmission has decreased significantly.

Topics about influenza B overtaking influenza A as the most transmissible virus have been trending on China’s social media platforms in recent days.

The proportion of influenza B cases in the outpatient department of the Children’s Hospital Affiliated to Shanghai Jiao Tong University, School of Medicine, has been rising significantly over the past two weeks, Qian Liling, doctor from the respiratory department of the hospital told thepaper.cn on Sunday.

According to Qian, based on the children visiting the hospital, there is no significant difference in symptoms caused by influenza A and influenza B and the proportion of cases requiring intensive care does not show a notable difference either. They both show a sudden onset of the disease with symptoms such as high fever, chills, sore throat, cough, and muscle aches all over the body. Patients’ temperatures can rise to 39C to 40C in several hours to 24 hours.

In response to some netizens suspecting that patients with influenza B tend to have a longer duration of illness compared to those infected with influenza A and have more severe symptoms, Qian said that patients infected with influenza B generally have milder symptoms compared with those with influenza A, but some influenza B patients may experience more noticeable gastrointestinal symptoms according to her multiple years’ clinical experience. However, the overall durations of both diseases are similar, ranging from five to seven days.

Influenza A usually has a higher transmissibility than influenza B and the previous global influenza pandemics have all been caused by influenza A, Qian said, adding that influenza A is more prone to occur genetic mutation.

Moreover, it is possible for patients to get infected with influenzas repeatedly during the influenza prevailing seasons since influenzas have different variants. However, the immunity generated after infection of a certain type of influenza usually lasts three to six months, according to Qian.

Qian noted that apart from taking medicines such as Oseltamivir and Baloxavir Marboxil for treatment of influenza infection, sufficient rest and sleep are closely related to good immunity and plays an important role in preventing influenza infection.