The annual incidences of hRSV for 2016, 2017 and 2018 were 1.19% (34/2855), 0.33% (16/4847) and 1.59% (18/1126), respectively, and those of HMPV were 0.14% (4/2855), 1.79% (87/4847), and 0.44% (5/1126), respectively. The frequency of symptoms in patients infected with human Respiratory Syncytial Virus (hRSV), Human Metapneumovirus (HMPV), Influenza A (H1N1) and Influenza A(H3N2) are categorized into upper respiratory tract infections (URTIs), lower respiratory tract infections (LRTIs), and gastrointestinal symptoms. Coryza (runny nose) was most common in HMPV (85.4%), followed by Influenza A(H3N2) (72.3%), Influenza A(H1N1) (74.6%), and hRSV (70.6%). Sore throat was reported more frequently in Influenza A(H1N1) (56%) and Influenza A(H3N2) (55.2%) patients than in hRSV (50%) patients. LRTI symptoms such as cough were common across all viruses, with the highest frequencies of HMPV (97.9%) and Influenza A(H1N1) (97.3%). Shortness of breath was most reported in HMPV (22.9%), whereas hRSV, Influenza A(H1N1), and Influenza A(H3N2) showed similar frequencies (16–19%). The rate of chest pain was highest for HMPV (23.9%), followed by Influenza A(H3N2) (22.3%), while Influenza A(H1N1) (10.6%) had the lowest rate. Gastrointestinal symptoms such as nausea and vomiting were most common in Influenza A(H3N2) patients (46.1% and 67.1%, respectively), followed by Influenza A(H1N1) patients (37.3% and 32%). Chills and myalgia (muscle aches), headache and weakness were very common across all infections, ranging from 84.2 to 91.6% (Table 1).
The mean age of the hRSV patients was 40.26 years, and that of the HMPV patients was 34.4 years. Leucopenia was most frequently observed in Influenza A(H1N1) patients (31.8%), whereas thrombocytopenia was most common in hRSV patients (28%). Neutrophilia (> 70%) was more common in Influenza A(H1N1) (52.1%) and HMPV (41.7%) patients. Liver function abnormalities, including elevated aspartate transaminase (AST) and alanine transaminase (ALT) levels, were most prevalent in hRSV (44.1% and 35.3%, respectively) and Influenza A(H1N1) (43.9% and 28.7%) patients. Alkaline phosphatase levels were frequently elevated across all groups. Inflammatory markers, such as C-reactive protein (CRP), were elevated in nearly half of the patients across all infections (Table 2). Notably, the total leukocyte count, platelet count, alkaline phosphatase (ALP) level and total protein level significantly differed among the hRSV and HMPV groups. The platelet count is significantly greater in HMPV compared to Influenza A(H1N1) and hRSV (Fig. 1). The total leukocyte count is also significantly greater in HMPV compared to Influenza A(H1N1), hRSV and Influenza A(H3N2). ALP levels are lower in hRSV than in the other groups, and total protein levels are significantly lower in Influenza A(H1N1) patients. Additionally, body temperature is significantly elevated in individuals with Influenza A(H1N1). Other parameters, such as the CRP level, erythrocyte sedimentation rate (ESR), respiratory rate, and diastolic blood pressure, did not significantly differ among the groups.
Comparative analysis of hematological and biochemical parameters in patients with hRSV, HMPV, Influenza A (H1N1), and Influenza A (H3N2) infections. The line represents the median; the gray band in the graphs indicates the normal range. Statistical significance (p value and 95% CI) was determined by one-way ANOVA followed by Tukey’s multiple comparisons test. Graphs were generated via GraphPad Prism version 8.4.2
Coryza and sore throat are consistently highly prevalent across all infections, particularly in the early days. Shortness of breath is initially low but increases notably in HMPV cases by days 6–8. Chest pain, nausea, vomiting, and abdominal pain exhibit fluctuating patterns, with some spikes observed later in the illness. Chills and myalgia remain prevalent throughout, especially in Influenza A(H3N2) and Influenza A(H1N1) cases, with myalgia showing the highest overall consistency. Joint pain and headache also followed variable trends, but headache remained notably high in all groups. Overall, while some symptoms, such as cough, chills, and myalgia, are common and persistent, others, such as shortness of breath and gastrointestinal symptoms, are more variable, potentially indicating differing disease severity and symptom progression among viral infections (Fig. 2).
Temporal progression of various symptoms in patients infected with HMPV, Influenza A (H1N1), Influenza A (H3N2) and hRSV over the course of illness
The total leukocyte count remains relatively stable, with a slight decline in some cases, whereas the neutrophil percentage decreases over time, particularly in hRSV cases, with a corresponding increase in the lymphocyte percentage. Platelet levels fluctuate, with noticeable dips in hRSV and Influenza A(H1N1) cases. Liver function markers, including AST and ALT, show intermittent peaks, particularly in hRSV and Influenza A(H1N1) infections, whereas ALP levels exhibit variable spikes. Inflammatory markers such as ESR and CRP fluctuate, with CRP peaking prominently for around 3–5 days in hRSV and HMPV patients. Urea and creatinine levels remain relatively stable, with slight elevations in later illness stages, particularly in HMPV and Influenza A(H3N2) patients. Body temperature remains at approximately 99–100 °F across all infections, with minor fluctuations (Fig. 3).
Temporal trends in various laboratory parameters in patients infected with HMPV, Influenza A (H3N2), Influenza A (H1N1), or hRSV over the course of illness
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