China's current flu infection remains at the level of seasonal disease like before COVID: CDC chief epidemiologist

China’s current flu infection still remains at the level of a seasonal flu like in previous years before the COVID-19 epidemic, Wu Zunyou, chief epidemiologist of the Chinese Center for Disease Control and Prevention (China CDC), said on Tuesday in response to the public’s concerns over the current influenza spreading that shows an upward trend. 

The annual influenza outbreak has entered its high level lately with the influenza A (H1N1) virus sweeping across the country in a matter of weeks, bringing up the proportion of influenza-like illnesses in both southern and northern areas. A total of 390 influenza-like illness outbreaks were reported nationwide during the eighth week of 2023 between February 20 and 26. 

The alternating seasons of winter and spring is a period with high incidence of respiratory infectious diseases when influenza cases in China show an upward trend, Wu said in a Sina Weibo post on Tuesday. 

Wu said that monitoring data from the sentinel hospitals nationwide set up by the China CDC shows that among influenza-like illness cases with the major indicator of a temperature above 38 C accompanied by cough or sore throat, the positive rates of infections with influenza virus have risen significantly in recent weeks from 0.7 percent between January 30 and February 5 to 4.1 percent between February 6 and February 12. The positive rates of influenza virus continued to rise to 14.3 percent between February 13 and 19 and further rose to 25.1 percent between February 20 and 26. 

Based on that trend, Wu predicted that the flu epidemic will continue for a couple of weeks but compared with the situation in the same period before the COVID-19 epidemic, China’s current flu epidemic is still at the level of a seasonal flu. 

He explained that the prevention measures against COVID-19 in the past three years also prevented the spreading of influenza, which led to the decreased immunity of the population toward influenza and provided favorable conditions for the spreading of the virus. 

He also noted that there is no cross-protection against each other between COVID-19 and influenza thus infection of COVID-19 recently would not protect people from contracting the influenza viruses. 

In terms of the COVID-19 epidemic, Wu said that the current epidemic situation presents the smearing phenomenon of the nationwide epidemic with the main characteristics of low-level prevalence with sporadic cases and local clusters of cases. Over the past week, the daily number of positive infections for COVID-19 remained over 10,000. 

Based on the global COVID-19 situation and the monitoring on mutated strains of the virus, as well as China’s tracing and observation on these mutant strains, Wu thinks they will not cause a new wave of COVID-19 in the near future. 

According to China CDC, monitoring on the mutants of the viral strains shows that all the prevalent variants in China since December 1, 2022 are Omicron variants of 44 lineages. The predominant lineages are BA.5.2.48 (60.0 percent) and BF.7.14 (29.2 percent). Besides, the composition of the predominant strains in cases reported in February is basically consistent with that in December 2022 and January this year. 

China CDC also detected 30 mutant strains that have to be attached great importance to, including XBB.1, XBB.1.5, XBB.1.5.5, XBB.1.9, BQ.1, BQ.1.1, BQ.1.1.17, BQ.1.2 and BQ.1.8.