People around you have fever again? Don't worry! The culprits are influenza A and norovirus

"Is the epidemic coming again? Everything was normal at work yesterday, but I suddenly felt cold at work today, and the temperature was over 38 degrees Celsius!"

"My colleagues quickly fell ill and developed fevers one after another. I was the one who was instantly surrounded by the 'heat wave'..."

"From sore throat to headache, from body aches to fever, everything seems familiar, but the antigen test is still a bar every day..."

Recently, the topic of "fever" has once again attracted everyone's attention on social platforms, which makes people feel a little worried.

So, is there really a surge in fever cases now?

01

Data Display

There is no peak in the fever clinic yet

Judging from the information on social networks, we can feel everyone's anxiety and concern, but national monitoring data may give us another perspective on the situation.

A report dated February 15, 2023 on the website of the Chinese Center for Disease Control and Prevention [1] showed that the total number of patients visiting fever clinics nationwide (excluding Hong Kong, Macao and Taiwan) reached a peak of 2.867 million on December 23, 2022, and then declined continuously; after January 23, 2023, the number of patients fluctuated at a low level, reaching 128,000 on February 13, a decrease of 95.5% from the peak.

Trends in the number of patients treated in fever clinics (examination rooms) across the country. Data comes from reports from 31 provinces (autonomous regions, municipalities) and the Xinjiang Production and Construction Corps.

So what do the doctors on the front line say?

On February 18, the People's Daily interviewed Hu Yang, deputy director of the Department of Respiratory and Critical Care Medicine at Shanghai Pulmonary Hospital. Dr. Hu said that there are patients with fever every day, and he has not felt a significant increase in the number recently. Of course, the data from the fever clinic lags slightly, and some people with fever will also be treated at home, so the data from the fever clinic may not reflect the entire real situation in real time, but at least it can be said that there is no so-called "surge in the number of fever patients" at present.

However, even if you have a fever, you don't need to be too anxious, because some infectious diseases that are common in winter and spring can also cause fever. We already know these infectious diseases very well and can prevent them. Let's talk about them in detail.

02

The risk of influenza A continues to increase

Vaccines are needed urgently

More than a month ago, the US Centers for Disease Control and Prevention issued a reminder that the elderly and children should pay attention to influenza protection because there was a peak in influenza infection at the end of the year, with the peak infection in week 52 at the end of last year (the last month of 2022). In the fourth quarter of 2022, at least 20 million people in the United States were infected with influenza A virus (83% of the population were infected with H3N2 and 17% were infected with H1N1), of which 210,000 were hospitalized and 13,000 died from influenza infection (including 61 children).

U.S. Centers for Disease Control and Prevention influenza surveillance report. Image source: U.S. Centers for Disease Control and Prevention

The situation in China is slightly different. In the past three years (since March 2020), influenza has been at a very low prevalence level in my country. However, since the spring and summer of 2022, an abnormal peak of epidemic has occurred in southern my country (reaching the highest level in the same period in the past five years). This wave of outbreaks is mainly caused by the influenza A influenza virus H3N2 subtype (consistent with the trend of the epidemic in the United States last year).

The national influenza data reported by legal infectious diseases has been on a downward trend since July 2022. Data source: China Centers for Disease Control and Prevention, map by Chen Mozhao.

Since the end of last year, experts have repeatedly warned that the world is still in the midst of a pandemic and that medical resources may be in short supply for some time. Based on the analysis of epidemic data, we need to prepare for the possible risk of influenza and COVID-19 infections overlapping with each other.

Therefore, in the face of the recent trend of increasing fever, we should also consider the possibility of influenza A infection.

Fortunately, the flu vaccine can prevent infection to the greatest extent and reduce the occurrence of severe illness. The vaccine corresponding to this round of infection has been fully launched in my country. Because it takes 2-4 weeks after the flu vaccine to produce enough antibodies. Therefore, the American Academy of Pediatrics (AAP) and the Centers for Disease Control and Prevention (CDC) both recommend that the vaccine be administered as soon as possible after it is available. Throughout the flu season, as long as you have not been vaccinated, the unexpired flu vaccine is still available, and it is recommended to be vaccinated as soon as possible at any time. In the same flu season, people who have completed the vaccination do not need to be vaccinated again.

03

Diarrhea + fever? Be careful with Noru

In addition to the "H1N1 Assassin", the peak season for the Norovirus is from October to March of the following year. The disease it causes is called Norovirus Infectious Diarrhea, commonly known as "Winter Vomiting Disease". To be more precise, its symptoms should be "vomiting and diarrhea".

The specific symptoms are related to age. Children are more likely to experience vomiting, while adults mainly experience diarrhea. Other digestive tract symptoms include nausea, abdominal pain, etc. However, there are also systemic symptoms such as headache, fever, chills and muscle aches, which are similar to the symptoms of many other diseases.

The symptoms of norovirus infection are not serious, but it is highly contagious. According to the Shenzhen Municipal Center for Disease Control and Prevention [6], only 18 virus particles are needed to cause infection, and basically everyone can be infected, regardless of gender, age, or whether they have been infected before (norovirus mutates very quickly, and it is easy to be infected again after infection). Recently, it is the beginning of the school year, and classmates and friends who have not seen each other for a long time will inevitably get close to each other. In this situation, norovirus is particularly easy to cause large-scale spread in schools. When the children return home, they will infect everyone, young and old.

This state of high infection and clustered infection, as well as similar clinical symptoms, does easily make people think of "re-positivity". However, as long as good care is taken and dehydration is avoided, most people will recover quickly.

04

Prevention and control are nothing more than three tricks

Pay attention at all times

Regardless of the type of infection, all infection prevention and control efforts focus on three areas: protecting susceptible populations, controlling sources of infection, and interrupting transmission routes.

To put it bluntly, patients who may transmit diseases should be isolated. If students/children are infected, parents should take them home to rest in time, which will facilitate their recovery and avoid infecting other children. They can return to school three days after the symptoms disappear. This is also suitable for adults in the workplace. On the one hand, for people who are susceptible to infection, they should be protected. For influenza A and COVID-19, they should be vaccinated, their hands should be kept clean, and masks should be worn when necessary.

Cutting off the transmission route means that the environment should be kept clean. If the patient vomits or has diarrhea, the environment should be disinfected and ventilation should be done to reduce the concentration of viruses in the air. We would like to remind everyone that the Norovirus may contaminate fruits, vegetables or shellfish and cause transmission, so these ingredients should be cleaned and properly cooked.

References:

[1] China Center for Disease Control and Prevention, “National Novel Coronavirus Infection Situation”

[2] http://henan.china.com.cn/health/2023-02/19/content_42264258.htm

[3] https://www.cdc.gov/flu/weekly/

[4] https://www.cdc.gov/flu/weekly/index.htm

[5] Transcript of the press conference held by the Joint Prevention and Control Mechanism of the State Council on August 10, 2022. http://www.nhc.gov.cn/xcs/xxgzbd/202208/c2be77648c8640f0bf9c9dfbfb9c8430.shtml

[6] https://mp.weixin.qq.com/s/X2A5OCnO38jBTXKHB-ixCw

Author: Chen Mozhao

Review | Tang Qin, Chief Researcher, Science Popularization Department, Chinese Medical Association

This article is produced by "Science Popularization China". Please indicate the source when reprinting.