Utility of cranial MRI in non-traumatic headache patients with prior negative head CT within 1 month.

AIM: To investigate the importance of additional cranial magnetic resonance imaging (cMRI) in non-traumatic headache patients with a prior negative head computed tomography (CT) examination within 1 month. MATERIALS AND METHODS: This retrospective study analysed 162 adult patients with non-traumatic headache who underwent cMRI within 1 month of a negative initial head CT at the emergency department (ED). The diagnostic yield and false-referral rate were analysed according to the revisit duration (early [≤1 week] versus late [>1-4 weeks] revisits), patient care settings (ED versus outpatient clinics [OPC]), and clinical variables. Subsequent patient management change (PMC), such as admission and treatment (AT) or outpatient clinic treatment (OT), were also investigated. RESULTS: The overall diagnostic yield of cMRI was 17.3% (28/162) and the false-referral rate was 1.2% (2/162). The diagnostic yield of cMRI was significantly different according to the patient care settings (ED, 24.7% [21/85] versus OPC, 9.1% [7/77]; p=0.02). The diagnostic yield was highest in the ED-early-revisit group (25.4% [18/71]), 45% (9/20) in those with systemic signs, and 46.7% (14/30) in those with symptom change. Among patients with positive cMRI findings, 90% (27/30) received AT and 3.3% (1/30) received OT. Among OPC-revisit-negative cMRI patients, PMC occurred in 0% (0/50). CONCLUSION: The diagnostic yield of cMRI was relatively high for headache patients who revisited the ED earlier, especially in those with systemic signs or symptom change. Most positive cMRI cases experienced PMC. Negative cMRI in OPC-revisit patients might help clarify the benign nature of a condition.

Clinical judgement perplexed by initially undisclosed use of herbal medicine and unexpected cross-reactivity of immunoassay.

We report a case of symptomatic bradycardia caused by consumption of a Chinese herbal medicine which was initially undisclosed to the attending emergency physician. The scientific name of the herb is Panax japonicus. Electrocardiogram revealed sinus bradycardia. Laboratory tests were normal except for the detection of a high serum digoxin level. Further interrogation of the patient eventually disclosed ingestion of the herb which, however, did not contain any digoxin. Other active ingredients in the herb include various types of ginsenoside. These are digoxin-like substances that had caused the observed false-positive detection of digoxin by fluorescence polarization immunoassay due to cross-reactivity. Our case-report provides an important insight about a blind-spot in the field of laboratory medicine (clinical pathology), namely, the false positive detection of digoxin due to crossreactivity in the immunoassay when we come across digoxin-like substances in clinical scenarios, which has barely received attention in the medical literature. It also conveys a clear educational message that with full understanding of the laboratory methodology and its mechanistic rationale there are actually some tricks-of-the-trade that allow us to optimize the specificity of the biochemical tests and the treatment of digoxin-like substances overdose.

Neurovascular Interactions in the Neurologically Compromised Neonatal Brain.

Neurological brain injuries such as hypoxic ischaemic encephalopathy (HIE) and associated conditions such as seizures have been associated with poor developmental outcome in neonates. Our limited knowledge of the neurological and cerebrovascular processes underlying seizures limits their diagnosis and timely treatment. Diffuse optical tomography (DOT) provides haemodynamic information in the form of changes in concentration of de/oxygenated haemoglobin, which can improve our understanding of seizures and the relationship between neural and vascular processes. Using simultaneous EEG-DOT, we observed distinct haemodynamic changes which are temporally correlated with electrographic seizures. Here, we present DOT-EEG data from two neonates clinically diagnosed as HIE. Our results highlight the wealth of mutually-informative data that can be obtained using DOT-EEG techniques to understand neurovascular coupling in HIE neonates.

Prevalence of pre-sarcopenia and sarcopenia in Hong Kong Chinese geriatric patients with hip fracture and its correlation with different factors.

INTRODUCTION: Sarcopenia and osteoporosis are age-related declines in the quantity of muscle and bone, respectively. Both contribute in disability, fall, and hip fracture in the elderly. This study reported the prevalence of sarcopenia in Chinese geriatric patients with hip fracture, and the correlation between relative appendicular skeletal muscle mass index and other factors. METHODS: This case series was conducted in Kowloon West Cluster Orthopaedic Rehabilitation Centre in Hong Kong. Data of all geriatric patients with primary hip fracture admitted to the above Centre from June to December 2014 were studied. Isometric grip strength, the maximal handgrip strength, was measured using a JAMAR hand dynamometer. Body composition including appendicular and whole-body lean body mass was measured using dual-energy X-ray absorptiometry. Pearson's correlation was used to examine the correlation between relative appendicular skeletal muscle mass index and other factors. RESULTS: A total of 239 patients with a mean age of 82 years were included in the study. Stratifying patients as male or female, the mean (± standard deviation) hand grip strength was 20.6 ± 7.3 kg and 13.6 ± 4.5 kg, the mean relative appendicular skeletal muscle mass index was 5.72 ± 0.83 kg/m(2) and 4.87 ± 0.83 kg/m(2), and the mean hip bone mineral density was 0.696 ± 0.13 g/cm(2) and 0.622 ± 0.12 g/cm(2), respectively. The prevalence of sarcopenia based on relative appendicular skeletal muscle mass index and hand grip strength according to the Asian Working Group for Sarcopenia definition was 73.6% in males and 67.7% in females. According to the European Working Group on Sarcopenia definition, the prevalence of pre-sarcopenia was 20.8% in males and 12.4% in females. Relative appendicular skeletal muscle mass index was positively correlated with hand grip strength, body weight, hip bone mineral density, body mass index, and total fat mass in males; and hand grip strength, body weight, body height, body mass index, and total fat mass in females. Except for body height in females, all correlations were statistically significant. CONCLUSION: The prevalence of sarcopenia was very high in geriatric hip fracture patients, and much higher than that in community-dwelling elderly population. Apart from the need to prescribe osteoporosis medicine, sarcopenia screening and treatment should be offered and is essential to reduce subsequent fall, subsequent fracture, fracture-related complications and economic burden to Hong Kong.

Antibiotic resistance and plasmid profiling of Vibrio spp. in tropical waters of Peninsular Malaysia.

Vibrio species isolated from four different sampling stations in the west coast of Peninsular Malaysia were screened for their antimicrobial resistance and plasmid profiles. A total of 138 isolates belonging to 15 different species were identified. Vibrio campbellii, V. parahaemolyticus, V. harveyi, and V. tubiashii were found to predominance species at all stations. High incidence of erythromycin, ampicillin, and mecillinam resistance was observed among the Vibrio isolates. In contrast, resistance against aztreonam, cefepime, streptomycin, sulfamethoxazole, and sulfonamides was low. All the Vibrio isolates in this study were found to be susceptible to imipenem, norfloxacin, ofloxacin, chloramphenicol, trimethoprim/sulfamethoxazole, and oxytetracycline. Ninety-five percent of the Vibrio isolates were resistant to one or more different classes of antibiotic, and 20 different resistance antibiograms were identified. Thirty-two distinct plasmid profiles with molecular weight ranging from 2.2 to 24.8 kb were detected among the resistance isolates. This study showed that multidrug-resistant Vibrio spp. were common in the aquatic environments of west coast of Peninsular Malaysia.

Alcohol consumption and persistent infection of high-risk human papillomavirus.

Alcohol consumption is a possible co-factor of high-risk human papillomavirus (HR-HPV) persistence, a major step in cervical carcinogenesis, but the association between alcohol and continuous HPV infection remains unclear. This prospective study identified the association between alcohol consumption and HR-HPV persistence. Overall, 9230 women who underwent screening during 2002-2011 at the National Cancer Center, Korea were analysed in multivariate logistic regression. Current drinkers [odds ratio (OR) 2·49, 95% confidence interval (CI) 1·32-4·71] and drinkers for ⩾5 years (OR 2·33, 95% CI 1·17-4·63) had a higher risk of 2-year HR-HPV persistence (HPV positivity for 3 consecutive years) than non-drinkers and drinkers for <5 years, respectively (vs. HPV negativity for 3 consecutive years). A high drinking frequency (⩾twice/week) and a high beer intake (⩾3 glasses/occasion) had higher risks of 1-year (OR 1·80, 95% CI 1·01-3·36) HPV positivity for 2 consecutive years) and 2-year HR-HPV persistence (OR 3·62, 95% CI 1·35-9·75) than non-drinkers. Of the HPV-positive subjects enrolled, drinking habit (OR 2·68, 95% CI 1·10-6·51) and high consumption of beer or soju (⩾2 glasses/occasion; OR 2·90, 95% CI 1·06-7·98) increased the risk of 2-year consecutive or alternate HR-HPV positivity (vs. consecutive HPV negativity). These findings suggest that alcohol consumption might increase the risk of cervical HR-HPV persistence in Korean women.

Transection of the obturator nerve by an electrosurgical instrument and its immediate repair during laparoscopic pelvic lymphadenectomy: a case report.

Obturator nerve injury seldom occurs in gynecologic surgery. However, gynecologic oncologic surgery, including pelvic lymph node dissection, increases the risk of this type of injury. Microsurgical techniques are usually performed for the repair of the nerve injury. Herein the authors report a case of obturator nerve injury caused by an electrosurgical instrument during laparoscopic pelvic lymphadenectomy, and its prompt repair by laparoscopic procedure in a 44-year-old patient with cervical cancer.

Effects of dietary levels of glycine, threonine and protein on threonine efficiency and threonine dehydrogenase activity in hepatic mitochondria of chicks.

This study was carried out to evaluate the relationship between threonine (Thr) efficiency and Thr dehydrogenase (TDG) activity as an indicator of Thr oxidation on chicks fed with levels of diets (CP [17.5% and 21.5%] and Thr [3.8 and 4.7 g/100 g CP]; glycine [Gly][0.64% and 0.98%] and true digestible Thr [dThr] [0.45% and 0.60%]). Calculation of the Thr efficiency was based on N-balance data and an exponential N-utilization model, and TDG activity was determined as accumulation of aminoacetone and Gly during incubation of hepatic mitochondria. This study found that in the liver of chicks who received a diet containing up to 0.79% Thr (4.7 g Thr/100 g of CP) in the 17.5% CP diet, no significant (p>0.05) effect on TDG activity was observed. However, significantly (p = 0.014) increased TDG activity was observed with a diet containing 21.5% CP (4.7 g Thr/100 g of CP) and the efficiency of Thr utilization showed a significant (p = 0.001) decrease, indicating the end of the Thr limiting range. No significant (p>0.05) effect on the total TDG activity and accumulation of Gly was observed with addition of Gly to a diet containing 0.45% dThr. In addition, addition of Gly to a diet containing 0.60% dThr also did not result in a change in accumulation of Gly. Due to an increase in accumulation of aminoacetone, an elevated effect on total TDG activity was also observed. No significant (p>0.05) reduction in the efficiency of Thr utilization was observed after addition of Gly at the level of 0.45% dThr. However, significantly (p<0.001) reduced efficiency of Thr utilization was observed after addition of Gly at the level of 0.60% dThr. Collectively, we found that TDG was stimulated not only by addition of Thr and protein to the diet, but also by addition of Gly, and efficiency of Thr utilization was favorably affected by addition of Gly at the level near to the optimal Thr concentration. In addition, no metabolic requirement of Gly through the TDG pathway was observed with almost the same accumulation of Gly and a slight increase in TDG activity by addition of Gly. Thus, our findings suggest that determination of TDG activity and parameter of efficiency of Thr utilization may be useful for evaluation of dietary Thr level.

A case of prolonged fever and a diagnosis obscured by an opaque sinus.

Prolonged fever in patients can be a diagnostic challenge. Clinicians generally consider infectious diseases, malignant diseases and collagen vascular diseases as possible causes of pyrexia of unknown origin (PUO). Even after extensive evaluation as many as 15 percent of patients with prolonged fever may remain undiagnosed. This case report describes subacute thyroiditis as a cause of prolonged fever and documents how that diagnosis was finally made after 40 days of fever.

Intrarectal administration of mCRAMP-encoding plasmid reverses exacerbated colitis in Cnlp(-/-) mice.

Cathelicidin is a pleiotropic host defense peptide secreted by epithelial and immune cells. Whether endogenous cathelicidin is protective against ulcerative colitis, however, is unclear. Here we sought to delineate the role of endogenous murine cathelicidin (mCRAMP) and the therapeutic efficacy of intrarectal administration of mCRAMP-encoding plasmid in ulcerative colitis using dextran sulfate sodium (DSS)-challenged cathelicidin-knockout (Cnlp(-/-)) mice as a model. Cnlp(-/-) mice had more severe symptoms and mucosal disruption than the wild-type mice in response to DSS challenge. The tissue levels of interleukin-1ß and tumor necrosis factor-α, myeloperoxidase activity and the number of apoptotic cells were increased in the colon of DSS-challenged Cnlp(-/-) mice. Moreover, mucus secretion and mucin gene expression were impaired in Cnlp(-/-) mice. All these abnormalities were reversed by the intrarectal administration of mCRAMP or mCRAMP-encoding plasmid. Taken together, endogenous cathelicidin may protect against ulcerative colitis through modulation of inflammation and mucus secretion.

Association of KIR genes and HLA-C alleles with HPV-related uterine cervical disease in Korean women.

This study investigated whether killer-cell immunoglobulin-like receptor (KIR) genes and human leukocyte antigen (HLA)-C alleles, receptors and ligands of natural killer cells are associated with the development of human papillomavirus (HPV)-related cervical disease in Korean women. Blood samples from 132 women with HPV-related cervical disease and 159 women without HPV infection were collected for genotyping of KIR genes and HLA-C alleles. Although no relationship was found between KIR genes and HPV-related cervical disease, a significant relationship was found between HLA-C alleles as ligands of KIR and HPV-related cervical disease. Women with HPV-related cervical disease were found to be significantly more likely to carry HLA-C*0303, particularly those with HPV 16 or 18 infection, and less likely to carry HLA-C*01 compared to women without HPV infection. HLA-C*0303 was found to confer susceptibility to HPV-related cervical disease, whereas HLA-C*01 was found to confer a protective effect against HPV-related cervical disease.

Bisphosphonate treatment may reduce osteoporosis risk in female cancer patients with morphine use: a population-based nested case-control study.

UNLABELLED: Chronic use of morphine is a risk factor for endocrinopathy and osteoporosis. Bisphosphonates accentuated the protective effect to develop osteoporosis in female patients with malignancy with morphine treatment. INTRODUCTION: This study investigates the risk of osteoporosis associated with morphine use by comparing the incidence of osteoporosis in female cancer patients treated with and without morphine. METHODS: A population-based nested case-control retrospective analysis was performed using the Longitudinal Health Insurance Database 2000 and Registry for Catastrophic Illness Patients of Taiwan. A malignancy cohort of 12,467 female patients without a history of osteoporosis during 1998-2010, and then 639 patients who subsequently developed osteoporosis as the osteoporosis group, were evaluated. Control-group patients were selected from the malignancy cohort without osteoporosis and frequency matched to each osteoporosis case 2:1 for age, year of cancer diagnosis, and index year. Logistic regression was used to estimate the odds ratios and 95% confidence intervals, and the multivariable model was applied to control for age. RESULTS: Female cancer patients who received morphine had a 10% lower risk of developing osteoporosis than non-morphine users, but this risk reduction was not significant. For patients treated with bisphosphonates, the morphine group had significantly lower odds in developing osteoporosis than the non-morphine group. CONCLUSION: Morphine treatment is not associated with the incidence of osteoporosis, and bisphosphonates accentuated the protective effect of morphine in the development of osteoporosis in female patients with malignancy in Taiwan.

Diagnostic value of CA125 as a predictor of recurrence in advanced ovarian cancer.

PURPOSE: The aim of this study was to establish the guidelines for detecting early recurrences of advanced epithelial ovarian cancer by use of the CA-125 level. MATERIALS AND METHODS: Eighty-five of the patients who met the inclusion criteria were enrolled in this study. The authors examined 25 incremental changes of CA125 from one to 25 IU/ml, and compared the CA-125 value with other prognostic factors. Increases in the CA-125 level from the nadir level were expressed as CA-125- increments. RESULTS: Among the 25 increments, a CA-125-8 (eight IU/ml) was selected as the predictor that was the most efficient and time-effective. CA-125-8 had a sensitivity of 91.5%, a specificity of 84.6%, a positive predictive value of 93.1%, a negative predictive value of 81.5%, an efficiency of 89.4%. and a median lead-time of 68.5 days (p <0.0001). CONCLUSION: The authors suggest the incremented CA-125-8 as a predictor of recurrent advanced ovarian cancer.

Low Intake of Choline Is Associated with Diminished Strength and Lean Mass Gains in Older Adults.

OBJECTIVES: Choline is an essential micronutrient for many physiological processes related to exercise training including biosynthesis of acetylcholine. Though dietary choline intake has been studied in relation to endurance training and performance, none have studied it during resistance exercise training (RET) in older adults. The objective of the study was to examine the relationship between choline intake and muscle responses to RET in older adults. METHODS: Forty-six, 60-69-year-old individuals (M=19, F=27) underwent 12 weeks of RET (3x/week, 3 sets, 8-12 reps, 75% of maximum strength [1RM], 8 exercises). Body composition (DEXA) and 1RM tests were performed before and after training. After analyzing 1,656 diet logs (3x/week, 46 participants, 12 weeks), participants' mean choline intakes were categorized into three groups: Low (2.9-5.5 mg/kg lean/d), Med-Low (5.6-8.0 mg/kg lean/d), or Adequate (8.1-10.6 mg/kg lean/d). These correspond to <50%, ~63%, and ~85% of Adequate Intake (AI) for choline, respectively. RESULTS: Gains in composite strength (leg press + chest press 1RM) were significantly lower in the Low group compared with the other groups (Low: 30.9 ± 15.1%, Med-Low: 70.3 ± 48.5%, Adequate: 81.9 ± 68.4%; p=0.004). ANCOVA with cholesterol, protein, or other nutrients did not alter this result. Reduced gains in lean mass were also observed in the Low group, compared with higher choline intake of 5.6-10.6 mg/kg lean/d (1.3 ± 0.6% vs. 3.2 ± 0.6%, p<0.05). CONCLUSION: These data suggest that this population of older adults does not consume adequate choline and lower choline intake is negatively and independently associated with muscle responses to RET.

Prevalence of parvoviruses in commercial turkey flocks.

Turkey parvovirus belongs to the family Parvoviridae, subfamily Parvovirinae, Genus parvovirus. Since the initial report on turkey parvovirus in the United States appeared in 1983, there had been no further reports of parvovirus in turkeys until 2008. The aims of our study were to determine the prevalence of parvovirus in commercial turkey flocks using PCR; to determine their genetic relationship to previous strains identified in North America and Europe; and to test samples for enteric viruses by transmission electron microscopy (TEM). A total of 169 fecal samples collected from 42 turkey farms in four different states within the United States between 2000 and 2010 were examined. We found that the most frequently detected viruses by TEM were small round viruses, accounting for 52% of the examined samples; however, the PCR detected parvoviruses in 71% of the samples. The phylogenetic analysis of partial nonstructural gene sequences showed a certain degree of variability among the turkey samples tested in the study. Moreover, there was a clear dichotomy in the phylogenetic tree between chicken and turkey samples, with the exception of one turkey isolate from 2000, which clustered together with the chicken group.

Nitric oxide and TNF-alpha trigger colonic inflammation and carcinogenesis in Helicobacter hepaticus-infected, Rag2-deficient mice.

Recombinase-activating gene-2-deficient (Rag2(-/-)) mice lacking functional lymphocytes provide a useful model of chronic inflammatory bowel disease-emulating events in human colon cancer. Infection of Rag2(-/-) mice with Helicobacter hepaticus led to accumulation of macrophages and neutrophils in the colon, a process temporally related to up-regulation of tissue inducible nitric oxide synthase (iNOS) expression at the site of infection and increased nitric oxide (NO) production, as evidenced by urinary excretion of nitrate. Progressive development of increasingly severe inflammation, hyperplasia, dysplasia, and cancer accompanied these changes. Concurrent administration of an iNOS inhibitor prevented NO production and abrogated epithelial pathology and inhibited the onset of cancer. The presence of Gr-1(+) neutrophils and elevated tumor necrosis factor-alpha (TNF-alpha) expression in colon were required for increased iNOS expression and cancer, whereas interleukin-10 (IL-10) down-regulated TNF-alpha and iNOS expression and suppressed cancer. Anti-inflammatory CD4(+) regulatory lymphocytes also down-regulated iNOS and reduced cancer formation. Collectively, these results confirm essential roles for inflammation, increased TNF-alpha expression, and elevated NO production in colon carcinogenesis.

Rapidly progressive hearing loss occurring over weeks: review of differential diagnoses.

BACKGROUND: Sudden hearing loss, or progressive hearing loss occurring over months to years, are well-established presentations. However, little is described in the medical literature on how to approach patients presenting with a rapidly progressive hearing loss occurring over weeks. This study aimed to evaluate the clinical significance of patients presenting with rapidly progressive hearing loss. METHODS: A case of rapidly progressive hearing loss occurring over 12 weeks is presented. A PubMed literature review was performed to determine the evidence-based differential diagnoses for rapidly progressive hearing loss. RESULTS: Fifteen causes were identified for rapidly progressive hearing loss: intracranial aetiologies (meningioma, lymphoma, metastatic deposit, cavernous angioma, meningitis, superficial siderosis); paraneoplastic syndrome (small cell lung carcinoma, thymoma); inflammatory or autoimmune disorders (autoimmune inner-ear disease, sarcoidosis, vasculitis, Sjögren's syndrome); infective disorders (syphilis, human immunodeficiency virus); and medication-induced causes. CONCLUSION: Rapidly progressive hearing loss should be considered a 'red flag' symptom that warrants urgent action. Most causes are systemic or sinister in nature, and the patient's hearing loss can potentially be reversed.

Spontaneous regression of advanced-stage oropharyngeal squamous cell carcinoma.

BACKGROUND: Spontaneous regression is defined as the partial or complete disappearance of a malignant tumour proven by microscopic examination in the absence of any substantial treatment. This paper presents the case of an older woman whose advanced-stage tonsillar squamous cell carcinoma was noted to have spontaneously regressed at seven months. CASE REPORT: A 66-year-old woman presented with a 4-month history of dysphagia and odynophagia in September 2020. An exophytic tumour was seen on the right tonsil; this was diagnosed radiologically and histologically as a squamous cell carcinoma of the tonsils, with tumour-node-metastasis staging of T4aN0M0. The patient received best supportive care. Seven months later, the oropharyngeal lesion had disappeared, with no treatment. Subsequent computed tomography imaging showed radiological resolution of the previously noted right-sided oropharyngeal lesion. CONCLUSION: Several mechanisms of spontaneous regression are discussed. Further studies should review this case in conjunction with other reports of spontaneous tumour regressions, to elucidate underlying mechanisms.

The role of adjuvant radiotherapy in locally advanced T4 mandible squamous cell carcinoma in the N0 patient: a single centre experience.

In locally advanced oral squamous cell carcinoma (OSCC), namely that showing invasion of the mandible, demonstrating no high-risk (e.g. extranodal extension, positive margin) or intermediate-risk histopathological features (e.g. perineural invasion, lymphovascular invasion), the additional benefit of postoperative radiotherapy (PORT) currently remains uncertain. A retrospective review covering the period between January 1, 2010 and December 31, 2019 was conducted to identify patients from a single UK centre with locally advanced invasive mandibular OSCC defined as pT4a, with no nodal or distant metastasis (N0 M0). The primary outcome was to determine the disease-free survival and overall survival rates in the surgery + PORT group, in comparison to the surgery only group. Twenty-eight eligible patients were identified, with 13 patients in the surgery + PORT group and 15 patients in the surgery only group. A single patient in the surgery + PORT group developed disease recurrence and subsequently died (1/13) (median follow-up 5.24 years, range 2.13-10.71 years). No patient in the surgery only group developed disease recurrence or died (0/15) (median follow-up 5.13 years, range 1.37-10.93 years). It may be reasonable to consider omitting PORT in pT4a pN0 M0 OSCC of the mandible in patients who demonstrate no high- or intermediate-risk histopathological features, following multidisciplinary team discussion.

Pandemic and seasonal human influenza virus infections in domestic cats: prevalence, association with respiratory disease, and seasonality patterns.

Domestic cats have several features that make them ideal vehicles for interspecies transmission of influenza viruses; however, they have been largely overlooked as potential reservoirs or bridging hosts. In this study, we conducted serological surveillance to assess the prevalence of novel pandemic H1N1 as well as seasonal human influenza virus infections in domestic cats in Ohio. Four hundred serum samples collected from domestic cats (September 2009 to September 2010) were tested using a hemagglutination inhibition (HI) test. The seroprevalences of pandemic H1N1, seasonal H1N1, and H3N2 were 22.5%, 33%, and 43.5%, respectively. In addition, a significant association between clinical feline respiratory disease and influenza virus infection was documented. In this sample of cats, the prevalence of pandemic H1N1 did not follow the seasonality pattern of seasonal H1N1 or H3N2 influenza, similar to observations in humans. Pandemic H1N1 seroprevalence did not vary in relation to ambient temperature changes, while the seroprevalence of seasonal H3N2 and H1N1 influenza viruses increased with the decline of ambient temperature. Our results highlight the high prevalence of influenza virus infection in domestic cats, a seasonality pattern of influenza virus infection comparable to that in humans, and an association of infection with clinical respiratory disease.