1+1>2: Can co-infection of influenza and COVID-19 aggravate the patient's condition?

With the onset of the flu epidemic in southern my country, the topic of flu and COVID-19 co-infection has gradually entered the public eye. In May, Fudan University virologist Jiang Shibo introduced the "influenza-COVID-19 syndrome" (Flucovid) in a short commentary, which refers to patients with symptoms of both flu and COVID-19 infection.

Through relevant research and animal model analysis, researchers found that co-infection with influenza A virus and the new coronavirus may lead to an increase in the severity of COVID-19 and even cause people to suffer from more serious illnesses.

Recently, the proportion of influenza cases in the south is much higher than the same period in 2019-2022. Many hospitals in Guangdong, Fujian, Guangxi, Jiangxi and Hainan have seen a sharp increase in the number of patients in their fever clinics. Influenza is quietly approaching under the cover of the new crown.

The COVID-19 pandemic has not stopped, and we are hit hard by seasonal influenza. The double attack has brought about the COVID-19-influenza syndrome. How should we take preventive and control measures?

Written by Li Xiaowei and Xu Shilu

What would happen if influenza and the new coronavirus were co-infected?

As early as January 2 this year, Israel's "New News" reported the first case of "influenza-COVID syndrome", that is, a case of simultaneous infection with the new coronavirus and influenza virus. She was a young unvaccinated pregnant woman in Israel.

The sudden influenza outbreak in many places in southern my country this summer has once again brought the topic of COVID-influenza co-infection to the forefront.

So, what is influenza-COVID syndrome?

During the COVID-19 pandemic, the influenza virus did not stop. It spread over a large area in southern my country in the first half of this year. As a result, a term called "Flurona" (influenza-COVID-19 infection syndrome) frequently appeared on major news platforms.

"Flurona" is very similar to the earlier name "Delmicron" (Delta and Omicron recombinant strain), which makes it easy for people to mistakenly believe that Fluorona is the name of a recombinant virus like Delmicron, but in fact it is not.

On May 19, Fudan University virologist Jiang Shibo and other scholars published a short commentary in the Journal of Medical Virology (J Med Virol) titled "Disease of influenza virus and SARS-CoV-2 coinfection: Flurona or Flucovid?", analyzing the characteristics of influenza-Omicron co-infection.

To avoid misunderstanding, Jiang Shibo and others proposed a more accurate term to replace Fluorna, namely Flucovid (influenza-COVID-19 syndrome), indicating that the patient has symptoms of both influenza and COVID-19 infection.

Next, we will analyze Professor Jiang Shibo’s article from the two aspects of patient symptoms and viral infection rate.

Judging from the clinical manifestations of patients, the symptoms of influenza and COVID-19 are similar, such as fever, dry cough, fatigue, headache, shortness of breath, loss of taste or smell, etc. However, patients with co-infection of influenza and COVID-19 will not have cold symptoms (such as sneezing, runny nose, nasal congestion, sore throat, back pain, etc.), and the nucleic acid test results of patients will be positive for influenza and COVID-19.

Comparison of the main symptoms of COVID-19, influenza and colds

From the perspective of viral infection rate, Jiang Shibo and other scholars pointed out in this paper that according to an analysis of 54 relevant literature, the overall proportion of co-infection with influenza virus among COVID-19 positive patients was 0.7%; another 18-month study of 17,011 adults infected with the new coronavirus showed a 1.3% influenza virus co-infection rate.

What is the risk of co-infection?

Some co-infection patients may also have undetectable influenza virus when they are diagnosed with COVID-19 (the incubation period and virus shedding period of influenza are shorter than those of COVID-19). Therefore, the actual co-infection rate may be much higher than the above values.

Among children, the proportion of influenza-COVID-19 co-infection (3.2%) was significantly higher than that of adult patients (0.3%), indicating that children are more susceptible to influenza-COVID-19 co-infection.

More importantly, among critically ill patients with COVID-19, the proportion of influenza-COVID-19 co-infection was 2.2%, higher than that of patients infected with COVID-19 alone (0.6%), indicating that co-infection with influenza virus may aggravate the severity of COVID-19.

In addition, animal studies have shown that compared with infection with influenza A virus or new coronavirus alone, co-infection can lead to more severe weight loss and lung inflammation damage, as well as increased tissue cytokine/chemokine expression levels. Therefore, co-infection with influenza and new coronavirus may also cause more severe diseases in humans.

To summarize, the researchers came to the following conclusions: 1. The infection rate of influenza-COVID-19 co-infection is higher in the vulnerable group of children; 2. Simultaneous infection of influenza and COVID-19 will cause the patient's symptoms to worsen and even develop other serious diseases.

Currently, abnormal seasonal influenza has occurred in southern my country in the summer. The global tension caused by Omicron BA.4/5 has not yet subsided, and such an abnormal influenza epidemic has occurred again. How should we respond?

The influenza virus is raging in the south. How can we prevent and control it?

Let's first review the current status of the influenza outbreak in southern my country. According to data from the National Influenza Center, influenza viruses have entered their peak season in summer in many southern provinces. In previous years, the peak season for influenza should be in the autumn and winter, but recently, abnormally, an outbreak has occurred in seven southern provinces.

% of influenza-like cases reported by sentinel hospitals in southern provinces from 2019 to 2022 | Image source: CDC

According to the National Center for Disease Control and Prevention (CDC), the positive rate of influenza virus testing in southern provinces continues to rise, and the proportion of cases is much higher than the same period in 2019-2022. Some provinces have entered the peak incidence period in summer, mainly influenza subtype A virus (H3N2).

The COVID-19 pandemic has not yet ended, and many people are worried about "Omicron BA.4/5", but "abnormal summer flu epidemics" have occurred in many southern provinces. It is inevitable that people will think of influenza-COVID-19 co-infection, which may result in the consequence of 1+1>2.

To this end, Jiang Shibo and others stated in the paper that it is recommended to treat influenza-COVID-19 syndrome by combining anti-influenza drugs and anti-COVID-19 drugs. In order to prevent influenza-COVID-19 syndrome, it is recommended to attach importance to the vaccination of influenza and COVID-19 vaccines (the interval between the two vaccinations should be greater than 14 days).

It is worth mentioning that at present, scientists around the world are accelerating the development of a universal COVID-19 vaccine, that is, a vaccine that can resist multiple COVID-19 strains, and perhaps it can be used to fight influenza-COVID-19 syndrome.

In fact, pharmaceutical companies have begun to develop new vaccines that can not only target influenza, but also be used to fight the new coronavirus. For example, the pharmaceutical company Novavax previously announced that a universal vaccine NVX-Cov2373 that can fight both the new coronavirus and influenza viruses has entered Phase 1/2 clinical trials.

Perhaps in the near future, we can use a universal vaccine to prevent multiple epidemics at the same time, such as COVID-19, influenza virus, etc. At present, we still need to strengthen physical protection measures and get COVID-19 and influenza vaccines as soon as possible to fight the current pandemic.

References

1. https://onlinelibrary.wiley.com/doi/10.1002/jmv.27874

2. https://m.peopledailyhealth.com/articleDetailShare?articleId=89e50c36270f44eb90a15b6607cecfe4

3. https://mp.weixin.qq.com/s/Ze_l2Tfdagnwc5d0PRF0qg

Produced by: Science Popularization China-Starry Sky Project

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