Key Factors Behind the Surge in Respiratory Infections in China

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Key Factors Behind the Surge in Respiratory Infections in China

Key Factors Behind the Surge in Respiratory Infections in China, According to Nature

Nature magazine has recently published a dedicated article addressing the surge in respiratory infections among children in China and explaining the possible reasons behind it [1].

The Cause Remains Common Pathogens

The article, citing a statement from the World Health Organization (WHO), emphasizes that the recent outbreak is primarily attributed to common winter infections rather than novel pathogens. It notes that this winter marks China’s first without COVID-19 restrictions since the pandemic erupted in 2020, leading to an expected peak in infections.

However, epidemiologists are drawing attention to the high incidence of pneumonia. WHO has requested the latest data, including laboratory results and trends in respiratory disease transmission, from China’s health authorities. Major pathogens include adenovirus, influenza virus, SARS-CoV-2, and RSV.

In recent months, there has been a significant increase in hospitalizations of children in mainland China, with a substantial proportion attributed to Mycoplasma pneumoniae, a common pathogen causing respiratory infections. While this pathogen typically results in relatively mild symptoms that do not require bed rest or hospitalization, its impact on children has been more significant this year.

During the recent National Day holiday, a lawyer named Q, a friend of mine, contracted a respiratory infection during a gathering, with symptoms more severe than those of COVID-19. Most attendees at the event also got infected, highlighting its strong contagiousness, later diagnosed as Mycoplasma infection.

In response to this situation, Dr. Benjamin Cowling, an epidemiologist at the University of Hong Kong, expressed that he is not surprised, considering it as a typical “winter acute respiratory infection wave.” He attributes the earlier appearance of cases this year to increased susceptibility to respiratory infections due to the added measures against COVID-19 over the past three years.

Key Factors Behind the Surge in Respiratory Infections in China, According to Nature

“Immunity Debt” as a Key Factor

The Nature article introduces the concept of “immunity debt” to explain why respiratory infections are severe this winter in mainland China. Other countries have also experienced a resurgence of common respiratory diseases in the first winter after relaxing pandemic control measures. For instance, in November 2022, the number of people hospitalized for influenza in the United States was the highest for the same period since 2010.

Dr. Jeremy Faust, an emergency physician and public health expert in the United States, also paid special attention to respiratory infections in mainland China on November 24. He used the term “immune naive” to describe a large group that, under strict public health controls, has not been exposed to a significant number of seasonal pathogens for several years, resulting in a lack of immune activation.

From 2020 to 2022, public health measures prevented the spread of seasonal pathogens, reducing people’s opportunities to develop immunity to these microorganisms. As a result, these pathogens, which would typically cause 2-3 colds (or occasional pneumonia) per season in children, began spreading in 2023 among a population with almost no immunity.

The Nature article also highlights the differences in the 2023 winter respiratory infections in mainland China compared to other countries. While some nations face influenza and RSV infections after the pandemic, mainland China experiences a higher prevalence of Mycoplasma pneumoniae infections. This is surprising because bacterial or mycoplasma infections usually occur opportunistically and often follow viral infections.

Professor Cowling notes that while pneumonia caused by bacteria is typically treated with macrolide antibiotics, overreliance on these drugs has led to drug-resistant pathogens. Research indicates that the resistance rate of Mycoplasma pneumoniae to macrolides in the Beijing region ranges from 70% to 90%. This resistance may contribute to the high hospitalization rate caused by Mycoplasma pneumoniae this year, as it hinders treatment and slows the recovery from Mycoplasma pneumoniae infections.