The PubMed database was searched using the terms “H5N1”, “SARS-CoV-2”, and “co-infection”, and this search revealed no articles on patients having a co-infection of H5N1 and SARS-CoV-2. According to previous reports, under proper supervision, the incidence rate of avian H5N1 influenza in humans has been decreasing in the past few years [6, 7]. However, the mortality rate due to severe acute respiratory distress induced by the H5N1 virus continues to be high [3]. In China, the implementation of “zero COVID” strategies was abandoned on 7 December 2022, after which a surge was recorded in the cases of infection with the Omicron variant of the SARS-CoV-2 [8]. Co-infection of the COVID-19 virus, particularly with the other pathogens responsible for pneumonia, has been attracting great attention since the beginning of the COVID-19 pandemic. According to reports, co-infection of SARS-CoV-2 with different influenza viruses leads to a higher fatality rate compared to infection with the COVID-19 virus alone [5]. Numerous cases of infection with both SARS-CoV-2 and influenza A virus were reported during the COVID-19 epidemic, while cases of co-infection with SARS-CoV-2 and H5N1 were scarce [9]. In the case discussed in the present study, no other member of the patient’s family was infected with H5N1, except for the patient, who had been exposed to sick poultry. Therefore, it was understood that the spread of the virus was limited to animal-to-human transmission only. Accordingly, it is recommended to ensure the protection of the upper respiratory tract of humans against droplets containing AIVs, particularly during contact with infected chickens and birds.
The CT images of the patient revealed interstitial infiltrates, lung consolidation, diffuse ground-glass opacities, and air bronchogram, all of which are symptoms observed during a common viral infection [10]. The typical features of COVID-19 in CT images include bilateral multi-lobar ground-glass opacities, which were not detected in the CT images of the discussed patient. The WHO has defined two types of SARS-CoV-2 variants: the variants of concern (VOCs) and the variants of interest (VOIs). Several VOCs have caused multiple waves of epidemics, including Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), Delta (B.1.617.2), and Omicron (B.1.1.529) [11]. The Omicron variant was first detected in China in December 2021. The prevalence of the Omicron variant in patients presented with a greater frequency of bronchial wall thickening and less-typical CT patterns [12]. However, the lesions occurring simultaneously in the central and peripheral regions of the lung and pleural effusion were uncommon in the cases of COVID-19. The clinical presentations were the same as those observed in the cases of isolated H5N1 infection and atypical for the pneumonia of COVID-19. Higher viral loads were evident in the BALF compared to the nasopharyngeal samples. Therefore, a single examination for the influenza virus, such as PCR for throat swabs, usually exhibited a relatively low sensitivity. [3]. In the event of viral pneumonia, timely antiviral treatment is key to decreasing mortality [9]. Therefore, for the case discussed in the present report, the mNGS of the BALF samples and the PCR test were performed at the earliest to verify the diagnosis, and this played a vital role in elucidating the etiology of viral pneumonia [13]. After the diagnosis, considering that the infection was caused by two viruses, the corresponding two categories of antiviral medicine were prescribed. While previous studies have demonstrated that co-infection with influenza and COVID-19 leads to a poor prognosis, the administration of both antiviral and anti-inflammation treatment in the present case could relieve lung inflammation, leading to an excellent prognosis.
In conclusion, it is important to state that co-infection of H5N1 and SARS-CoV-2 in patients may not lead to a terrible prognosis if timely treatment is administered. Indeed, influenza A virus infection can elevate ACE2 expression to promote the infectivity of SARS-CoV-2. [14] However, despite the absence of any severe or adverse events in the disease course of the present case that had a co-infection of H5N1 and SARS-CoV-2, it is recommended to ensure further precise treatment by verifying the pathogen responsible for causing severe pneumonia through various examinations.
