Monitoring epidemic viral respiratory infections using one-step real-time triplex RT-PCR targeting influenza A and B viruses and respiratory syncytial virus

Rapid and specific diagnosis of influenza A/B and respiratory syncytial virus (RSV) viruses is needed for optimal management of patients with acute respiratory infections. In this study, a one‐step triplex real‐time RT‐PCR assay was developed for rapid diagnosis of influenza A/B and RSV infections to optimize diagnosis efficiency of acute respiratory infections. Cell‐culture supernatants and clinical samples were used to evaluate specificity and sensitivity of the assay. The assay was used routinely during two winter epidemics for testing respiratory specimens from 2,417 patients. The limit of detection in cell‐culture supernatant was 1–10 plaque forming units/input (influenza A/B) and 2 × 10^?2 50% tissue culture infectious dose/input (RSV). In clinical samples, the assay was as sensitive as commercial molecular assays for the detection of each influenza A/B and RSV (Flu‐A/B and RSV‐A/B r‐gene?) individually, and far more sensitive than antigen detection. During the winter 2008–2009, the assay identified 145 RSV, 42 influenza A, and one mixed RSV‐influenza A infections among 298 patients. The next winter, the assay was used in two independent hospital laboratory settings. 776 patients were tested in one hospital and 1,343 in the other, resulting in 184 and 501 RSV, 133 and 150 influenza A, and 1 and 11 mixed RSV‐influenza A infections, respectively, being detected. This new user‐friendly assay allows rapid (within hours), effective molecular diagnosis of single or mixed infections involving influenza A (including seasonal A H1N1 and H3N2, and A(H1N1) 2009), influenza B, and RSV(A/B). The assay is very valuable for managing patients during winter epidemics when influenza and respiratory syncytial viruses co‐circulate. J. Med. Virol. 83:695–701, 2011. © 2011 Wiley‐Liss, Inc.     

Hospital‐based influenza surveillance in Korea: Hospital‐based influenza morbidity and mortality study group

Influenza epidemics occur annually with variations in size and severity. Hospital‐based Influenza Morbidity & Mortality was established to monitor influenza epidemics and their severity, which is composed of two surveillance systems: emergency room‐based and inpatient‐based surveillance. Regarding emergency room‐based surveillance, influenza‐like illness index (influenza‐like illness cases per 1,000 emergency room‐visiting subjects), number of laboratory‐confirmed cases and the distribution of influenza types were estimated weekly. Inpatient‐based surveillance included monitoring for hospitalization, complications, and mortality. The emergency room influenza‐like illness index correlated well with the number of laboratory‐confirmed influenza cases, and showed a bimodal peak at Week 4 (179.2/1,000 emergency room visits) and Weeks 13‐14 (169.6/1,000 emergency room visits) of 2012. Influenza A was the predominant strain during the first epidemic peak, while influenza B was isolated exclusively during the second peak. In 2011–2012 season, the mean admission rate of emergency room‐visiting patients with influenza‐like illness was 16.3% without any increase over the epidemic period. Among the hospitalized patients with influenza, 33.6% (41 out of 122 patients) were accompanied by complications, and pneumonia (28.7%, 35 out of 122 patients) was the most common. Most fatal cases were caused by influenza A (96.2%) after the first epidemic peak. In conclusion, Hospital‐based Influenza Morbidity & Mortality was effective for monitoring the trends in circulating influenza activity concurrently with its severity. In the 2011–2012 season, the influenza epidemic persisted for a ≥5‐month period, with a bimodal peak of influenza A and B in sequence. Overall, influenza A was more severe than influenza B. J. Med. Virol. 85:910–917, 2013. © 2013 Wiley Periodicals, Inc.     

Rapid discrimination of oseltamivir-resistant 275Y and -susceptible 275H substitutions in the neuraminidase gene of pandemic influenza A/H1N1 2009 virus by duplex one-step RT-PCR assay

Pandemic influenza A/H1N1 2009 (A/H1N1pdm) virus caused significant outbreaks worldwide last year (2009). A number of oseltamivir-resistant A/H1N1pdm viruses possessing an H275Y substitution in the neuraminidase (NA) protein were reported sporadically in several countries, including Japan, but they were sensitive to zanamivir and did not spread in the community. In this study, to monitor rapidly and simply oseltamivir-resistant A/H1N1pdm viruses possessing H275Y, a duplex one-step RT-PCR assay (H275Y RT-PCR assay) was developed based on an endpoint genotyping analysis method. H275Y RT-PCR assay evaluated using several subtypes/types of influenza A and B viruses and other respiratory pathogenic viruses and shown to have high sensitivity and high specificity. Forty-four clinical specimens were tested after RNA purification using the H275Y RT-PCR assay, resulting in one clinical specimen being found to contain a virus possessing the H275Y mutation. Seventy-three clinical isolates were then tested with the H275Y assay by using clinical isolates in the cultured supernatants of cells directly, without RNA purification, and the results were consistent with the NA sequencing. Since the H275Y RT-PCR assay could detect the H275Y mutation in clinical isolates without RNA purification, as well as a H275Y mutated virus in clinical specimens after RNA purification, the assay was considered a powerful tool for surveillance screening of oseltamivir-resistant A/H1N1pdm virus activity.     

Viral etiology of influenza‐like illnesses during the influenza season between December 2011 and April 2012

The aim of this study was to determine the frequency of respiratory viruses responsible for respiratory tract infections in Turkish children during the 2011–2012 influenza season. Nasal swabs were obtained from patients with symptoms suggestive of an influenza‐like illness between December 2011 and April 2012. Samples were analyzed with multiplex real‐time polymerase chain reaction (RT‐PCR) to help identify the causative viral pathogen. A total of 200 patients were enrolled in the study. A respiratory virus was detected successfully in 102 (51%) children; influenza A (H3N2) in 39.2%, influenza B in 23.5%, RSV in 15.6%, rhinovirus in 13.7%, bocavirus in 2.9%, coronavirus in 2.9%, and metapneumovirus in 0.9% of patients. Only one patient was co‐infected with bocavirus and influenza A virus. A statistically significant difference in the mean age of presentation was observed between the various viral pathogens (P < 0.001). Patients with RSV were significantly younger whereas children infected with the influenza viruses were significantly older. Comparison of symptoms revealed that fever and headache occurred more frequently with the influenza viruses than the other viruses combined (P < 0.001, <0.05). Durations of symptoms such as fever, cough, nasal congestion, and rhinorrhea were also significantly longer in the influenza group (P < 0.001, <0.005, <0.001, <0.005, respectively). Demographic analyses revealed that the school/daycare attendance was the only parameter associated with a significantly increased risk for influenza infection. With an overall viral pathogen detection rate of 51%, findings of the present study suggest other respiratory pathogens, whether viral or bacterial, may also lead to hospital visits due to influenza‐like illnesses in children. J. Med. Virol. 86:865–871, 2014. © 2013 Wiley Periodicals, Inc.

     

Functional immune response to influenza H1N1 in children and adults after live attenuated influenza virus vaccination

Influenza virus is a major respiratory pathogen, and vaccination is the main method of prophylaxis. In 2012, the trivalent live attenuated influenza vaccine (LAIV) was licensed in Europe for use in children. Vaccine‐induced antibodies directed against the main viral surface glycoproteins, haemagglutinin (HA) and neuraminidase (NA) play important roles in limiting virus infection. The objective of this study was to dissect the influenza‐specific antibody responses in children and adults, and T cell responses in children induced after LAIV immunization to the A/H1N1 virus. Blood samples were collected pre‐ and at 28 and 56 days post‐vaccination from 20 children and 20 adults. No increase in micro‐neutralization (MN) antibodies against A/H1N1 was observed after vaccination. A/H1N1 stalk‐specific neutralizing and NA‐inhibiting (NI) antibodies were boosted in children after LAIV. Interferon γ‐producing T cells increased significantly in children, and antibody‐dependent cellular‐mediated cytotoxic (ADCC) cell activity increased slightly in children after vaccination, although this change was not significant. The results indicate that the NI assay is more sensitive to qualitative changes in serum antibodies after LAIV. There was a considerable difference in the immune response in children and adults after vaccination, which may be related to priming and previous influenza history. Our findings warrant further studies for evaluating LAIV vaccination immunogenicity.     

Differential diagnosis of pandemic (H1N1) 2009 infection by detection of haemagglutinin with an enzyme-linked immunoassay

A sensitive and convenient immunoassay that can directly differentiate pandemic (H1N1) 2009 (pH1N1) virus from seasonal influenza virus can play an important role in the clinic. In the presented study, a double-sandwich ELISA (pH1N1 ELISA), based on two monoclonal antibodies against haemagglutinin (HA) of the pH1N1 virus, was developed. After laboratory determination of the sensitivity and specificity characteristics, the performance of this assay was evaluated in a cohort of 904 patients with influenza-like illness. All seven strains of pH1N1 virus tested were positive by pH1N1 ELISA, with an average lower detection limit of 10^{3.0 ± 0.4} tissue culture infective dose (TCID)₅₀/mL (or 0.009 ± 0.005 HA titre). Cross-reaction of the assay with seasonal influenza virus and other common respiratory pathogens was rare. In pH1N1-infected patients, the sensitivity of the pH1N1 ELISA was 92.3% (84/91, 95% CI 84.8–96.9%), which is significantly higher than that of the BD Directigen EZ Flu A + B test (70.3%, p <0.01). The specificity of pH1N1 ELISA in seasonal influenza A patients was 100.0% (171/171, 95% CI 97.9–100.0%), similar to that in non-influenza A patients (640/642, 99.7%, 95% CI 98.9–100.0%). The positive predictive value for pH1N1 ELISA was 97.7% and the negative predictive value was 99.1% in this study population with a pH1N1 prevalence of 10.1%. In conclusion, detection of HA of pH1N1 virus by immunoassay appears to be a convenient and reliable method for the differential diagnosis of pH1N1 from other respiratory pathogens, including seasonal influenza virus.     

Etiology of viral respiratory infections in Northern Lao People's Democratic Republic

In Lao People's Democratic Republic (PDR), acute respiratory infections overburden the health care system, but viral etiology, genetic diversity, and seasonality, especially in light of the introduction of influenza vaccination in the country, are poorly understood. From August 2010 to April 2011, 309 outpatients were recruited at the Luang Prabang Provincial Hospital covering highland Lao communities. Nasopharyngeal swabs were screened for the presence of 13 respiratory viruses. At least one virus was detected in 69.6% and dual/triple viral infections in 12.9%/1.9% of the patients. Influenza A and B viruses combined were the most frequently detected pathogens, followed by human adenovirus and respiratory syncytial virus (RSV). The other viruses were detected in less than 10% of the patients. Phylogenetic analyses on a representative set of RSV strains revealed that, while otherwise very rare, the RSV‐B CB1/THB genotype cocirculated with other common genotypes. A single wave of influenza virus and RSV activity was observed during the rainy season, providing further support to influenza vaccination before the onset of the rains. This study provides recommendations for influenza vaccination that still needs optimization and highlights the need for revised guidelines for treatment and prevention of respiratory infections in Lao PDR, as well as for increased surveillance efforts.     

Surveillance of 16 respiratory viruses in patients with influenza‐like illness in Nanjing,China

Much less is known about the etiology of influenza‐like illness in China. A continuous surveillance of 16 respiratory viruses was conducted from November 2010 to October 2011 of outpatients with influenza‐like illness in Nanjing, China. The two largest general hospitals and a provincial virus laboratory in Nanjing participated in this study. Throat swabs were collected from outpatients during medical visits for influenza‐like illness and were tested for 16 respiratory viruses using PCR. Three hundred seventeen viruses were detected in samples from 246 (50.6%) patients with influenza‐like illness. The viruses found mostly commonly were influenza, rhinovirus, hCoV HKU1, and adenovirus. The identification rates of respiratory viruses differed significantly among different sampling seasons (P = 0.0002). The rates of influenza A and hCoV HKU1 were much higher during the influenza‐like illness winter peak than during the influenza‐like illness summer peak and other months. Co‐infections were detected in 57 (11.7%) patients and were found most commonly in adults older than 60 years. RSV was detected in 5.9% and 2.6% of patients who were 0–5 and 6–15 years old, respectively, but was not detected in other age groups. This study confirmed that multiple respiratory viruses may circulate concurrently in the population and account for a large proportion of influenza‐like illness. In addition to influenza virus, hCoV HKU1 may be associated with the influenza‐like illness winter peak in Nanjing, China. J. Med. Virol. 84:1980–1984, 2012. © 2012 Wiley Periodicals, Inc.     

Viral pathogens among elderly people with acute respiratory infections in Shanghai,China: Preliminary results from a laboratory‐based surveillance, 2012‐2015

Acute respiratory infections (ARIs), with viral pathogens as the major contributors, are the most common illnesses worldwide, and increase the morbidity and mortality among the elderly population. The clinical and pathological features of elderly people with ARIs need to be identified for disease intervention. From January 1, 2012 through December 31, 2015, respiratory specimens from patients above 60 years old with ARIs were collected from the outpatient and inpatient settings of six sentinel hospitals in Pudong New Area. Each specimen was tested via multiplex polymerase chain reaction (PCR) for eight target viral etiologies including influenza, human rhinovirus (HRV), human para‐influenza virus (PIV), adenovirus (ADV), respiratory syncytial virus (RSV), human metapneumovirus (hMPV), human coronavirus (hCoVs), and human bocavirus (hBoV). A total of 967 elderly patients with ARIs were enrolled, including 589 (60.91%) males, and the median age was 73 years old. 306 (31.64%) patients were tested positive for any one of the eight viruses, including 276 single infections and 30 co‐infections. Influenza was the predominant virus (14.17%, 137/967), detected from 21.35% (76/356) of the outpatients and 9.98% (61/611) of the inpatients. Influenza infections presented two annual seasonal peaks during winter and summer. Compared with non‐influenza patients, those with influenza were more likely to have fever, cough, sore throat, and fatigue. This study identified influenza as the leading viral pathogen among elderly with ARIs, and two seasonal epidemic peaks were observed in Shanghai. An influenza vaccination strategy needs to be advocated for the elderly population.

     

Detection of influenza A virus by radioimmunoassay and enzyme-immunoassay from nasopharyngeal specimens

Four-layer (indirect) radioimmunoassay (RIA) and enzyme-immunoassay (EIA) techniques were developed for the detection of influenza A and B virus in the sonicated nasopharyngeal specimens from patients hospitalized for acute respiratory infection. Polystyrene beads (RIA) or polystyrene microtiter plates (EIA) were used as the solid-phase, guinea pig antivirus immunoglobulins as the catching antibodies, rabbit antivirus immunoglobulins as the secondary antibodies, and ¹²⁵I-labeled sheep antirabbit (RIA) or horseradish peroxidase conjugated swine antirabbit (EIA) immunoglobulins as the detector antibodies. A comparison of the developed RIAs and EIAs with the immunofluorescence (IF) method was made with 41 influenza A IF-positive and 150 influenza A IF-nega-tive specimens. Each of the 41 influenza A IF-positive specimens was positive by the influenza A RIA and negative by the influenza B RIA. Out of the 150 influenza A IF-negative specimens 3 specimens were found with weakly positive results in influenza A and B RIAs, but in each of these 3 specimens the binding proved nonspecific by the corresponding confirmatory tests. Using the EIA technique and the same immunoreagents as in RIA, identical results were obtained in each selected specimen tested. The developed RIAs and EIAs proved to be as specific and sensitive as the IF technique, and they should be practical in the diagnosis of respiratory infections directly from nasopharyngeal specimens.     

Comparing the Cobas Liat Influenza A/B and respiratory syncytial virus assay with multiplex nucleic acid testing

Influenza virus and respiratory syncytial virus (RSV) detection with short turn-around-time (TAT) is pivotal for rapid decisions regarding treatment and infection control. However, negative rapid testing results may come from poor assay sensitivity or from influenza-like illnesses caused by other community-acquired respiratory viruses (CARVs). We prospectively compared the performance of Cobas Liat Influenza A/B and RSV assay (LIAT) with our routine multiplexNAT-1 (xTAG Respiratory Pathogen Panel; Luminex) and multiplexNAT-2 (ePlex-RPP; GenMark Diagnostics) using 194 consecutive nasopharyngeal swabs from patients with influenza-like illness during winter 2017/2018. Discordant results were reanalyzed by specific in-house quantitative nucleic acid amplification testing (NAT). LIAT was positive for influenza virus-A, -B, and RSV in 18 (9.3%), 13 (6.7%), and 55 (28.4%) samples, and negative in 108 samples. Other CARVs were detected by multiplexNAT in 66 (34.0%) samples. Concordant results for influenza and RSV were seen in 190 (97.9%), discordant results in 4 (2.1%), which showed low-level RSV (<40 000 copies/mL). Sensitivity and specificity of LIAT for influenza-A, -B, and RSV were 100%, 100% and 100%, and 100%, 99.5% and 100%, respectively. The average TAT of LIAT was 20 minutes compared to 6 hours and 2 hours for the multiplexNAT-1 and -2, respectively. Thus, LIAT demonstrated excellent sensitivity and specificity for influenza and RSV, which together with the simple sample processing and short TAT renders this assay suitable for near-patient testing.     

Development of duplex real-time RT-PCR for detection of influenza virus A and B

Influenza viruses continue to be accountable for winter outbreaks. The potential for developing complications is higher in certain risk groups, such as children, the elderly and individuals with chronic medical conditions. We have presented a duplex real-time RT-PCR for detection of influenza A and B. The sensibility of our method was estimated at 0.01TCID(50)/ml for detection of influenza A and 0.1TCID(50)/ml for influenza B. Any other viruses with respiratory tract tropism were detected with our method. After that, we tested our duplex RT-PCR on 119 samples (nasal aspirates and liquids of broncho-alveolar washes) collected in the CHRU of Lille between November 2005 and January 2006 from patients aged one month to 81 years. Conventional methods such as direct immunofluorescence (IF) assay and/or cell culture were applied on these samples. Four samples were positive for influenza A virus detection and, in particular, one liquid of broncho-alveolar wash for which the direct IF assay was negative. Thus, our method is adapted to diagnosis of flu infections. Nevertheless, our duplex RT-PCR will be tested during a flu outbreak.     

Viruses associated with influenza‐like‐illnesses in Papua New Guinea, 2010

Influenza‐like‐illness can be caused by a wide range of respiratory viruses. The etiology of influenza‐like‐illness in developing countries such as Papua New Guinea is poorly understood. The etiological agents associated with influenza‐like‐illness were investigated retrospectively for 300 nasopharyngeal swabs received by the Papua New Guinea National Influenza Centre in 2010. Real‐time PCR/RT‐PCR methods were used for the detection of 13 respiratory viruses. Patients with influenza‐like‐illness were identified according to the World Health Organization case definition: sudden onset of fever (>38°C), with cough and/or sore throat, in the absence of other diagnoses. At least one viral respiratory pathogen was detected in 66.3% of the samples tested. Rhinoviruses (17.0%), influenza A (16.7%), and influenza B (12.7%) were the pathogens detected most frequently. Children <5 years of age presented with a significantly higher rate of at least one viral pathogen and a significantly higher rate of co‐infections with multiple viruses, when compared to all other patients >5 years of age. Influenza B, adenovirus, and respiratory syncytial virus were all detected at significantly higher rates in children <5 years of age. This study confirmed that multiple respiratory viruses are circulating and contributing to the presentation of influenza‐like‐illness in Papua New Guinea. J. Med. Virol. 86:899–904, 2014. © 2013 Wiley Periodicals, Inc.

     

Umifenovir susceptibility monitoring and characterization of influenza viruses isolated during ARBITR clinical study

Antiviral drugs can play a significant role in the control of influenza. Umifenovir (Arbidol) is licensed and widely used in Russia for the prophylaxis and/or treatment of influenza. We evaluated the susceptibility to umifenovir of reference influenza A and B viruses and influenza A viruses isolated from patients in the ARBITR clinical trial in 2012-2014 seasons. Using an MDCK cell-based enzyme-linked immunosorbent assay (ELISA), we showed that the replication of antigenically dominant human influenza A and B viruses was efficiently inhibited by umifenovir. The wild-type А/Perth/265/2009 (H1N1)pdm09, A/Fukui/45/2004 (H3N2), and B/Perth/211/2001 viruses and their oseltamivir-resistant counterparts were susceptible to umifenovir among in vitro laboratory assays. All 18 clinical isolates of influenza A viruses obtained before and during therapy were susceptible to umifenovir with 50% effective concentration (EC ₅₀) ranging from 8.4 ± 1.1 to 17.4 ± 5.4 µM. No molecular markers of umifenovir resistance were identified in influenza viruses isolate d from patients at 3, 5, and 7 days after initiation of therapy. None of the viruses isolated before and during umifenovir therapy displayed reduced susceptibility to neuraminidase (NA) inhibitors. Thus, umifenovir is effective against influenza viruses circulating in 2012-2014 seasons, and therapy did not lead to the emergence of drug-resistant variants.     

Lymphocytopenia as a marker for pandemic influenza A/H1N1 2009 virus infection in children

Lymphocytopenia has been reported in adults with pandemic influenza A/H1N1 2009 infection, but data in children are inconclusive. Data from 76 children presented with flu‐like symptoms between July and November 2009 and tested for pandemic influenza A/H1N1 2009 virus and white blood cell (WBC) counts were analyzed. Samples from 37 (48.7%) children resulted in a positive PCR assay for pandemic influenza A/H1N1 2009 virus. When comparing data from these children with data from 39 (51.3%) children with uncomplicated flu‐like illness and negative PCR assay for pandemic influenza A/H1N1 2009 virus, no difference in disease duration, median age, red blood cell count, hemoglobin concentration, C reactive protein concentration, and absolute neutrophil count was observed, whereas significant differences were apparent when considering WBC count, relative and absolute lymphocyte count, absolute lymphocyte count z‐score, and platelet count. Receiver operating characteristic curve analysis revealed that the best absolute lymphocyte count and absolute lymphocyte count z‐score cut‐points that simultaneously maximized sensitivity and specificity were 2,256 cells/µl and ?0.89, respectively, sensitivity being 0.81 (95% CI: 0.68–0.94), specificity 0.87 (95% CI: 0.77–0.98), positive predictive value 0.85 (95% CI: 0.74–0.97), and negative predictive value 0.83 (95% CI: 0.71–0.94). In conclusion, lymphocytopenia is a marker for influenza A/H1N1 2009 virus infection in children. Absolute lymphocyte count <2,556 cells/µl or absolute lymphocyte count z‐score < ?0.89 may be useful cut‐offs to discriminate against children at higher risk of infection during epidemics. Considering that the pandemic virus is highly likely to continue to circulate in the coming winter season, these findings provide direct and practical implications for the near future. J. Med. Virol. 83:1–4, 2011. © 2010 Wiley‐Liss, Inc.     

Evaluation of the Xpert Flu test and comparison with in-house real-time RT-PCR assays for detection of influenza virus from 2008 to 2011 in Marseille,France

Rapid documentation of respiratory specimens can have an impact on the management of patients and their relatives in terms of preventive and curative measures. We compared the results of the Xpert® Flu assay (Cepheid) with three real-time RT-PCR assays using 127 nasopharyngeal samples, of which 75 were positive for influenza A (with 52 identified as A/HINI-2009) and 52 were positive for influenza B. The Xpert® Flu assay presented a quasi-absence of non-interpretable tests, and showed sensitivity and specificity of 100% and 100% for Flu A, 98.4% and 100% for A/HINI-2009, and 80.7% and 100% for Flu B.     

Lopinavir/ritonavir is associated with pneumonia resolution in COVID‐19 patients with influenza coinfection: A retrospective matched‐pair cohort study

During the early stages of the pandemic, some coronavirus disease (COVID‐19) patients were misdiagnosed as having influenza, which aroused the concern that some deaths attributed to influenza were actually COVID‐19‐related. However, little is known about whether coinfection with influenza contributes to severity of COVID‐19 pneumonia, and the optimal therapeutic strategy for these patients. We retrospectively studied 128 hospitalized patients with COVID‐19 pneumonia. All patients were positive severe acute respiratory syndrome coronavirus 2 positive by nucleic acid detection. Sixty‐four cases were coinfected with influenza A/B and the other 64 were influenza negative, matched by age, sex, and days from onset of symptoms. Among the 64 coinfected patients, 54 (84.4%) were coinfected with influenza A, and 10 (15.6%) with influenza B. The median duration of viral shedding time from admission was longer for patients with influenza coinfection (17.0 days) than for those without influenza coinfection (12.0 days) (P < .001). The multivariable Cox proportional hazards model showed that the hazards ratio of resolution in lung involvement was 1.878 (P = .020) for patients administered lopinavir/ritonavir, compared with those not administered lopinavir/ritonavir (95% confidence interval: 1.103‐3.196). Among influenza coinfected patients, those treated with lopinavir/ritonavir exhibited faster pneumonia resolution within 2 weeks after symptom onset (37% vs 1%; P = .001). There was no difference in lung involvement between influenza coinfected and noninfected groups. Lopinavir/ritonavir eliminated the difference of lung involvement between influenza coinfected and noninfected groups, indicating that lopinavir/ritonavir is associated with pneumonia resolution in COVID‐19.