Pandemic (H1N1) 2009 and Seasonal Influenza A (H1N1) Co-infection, New Zealand, 2009

Co-infection with seasonal influenza A (H1N1) and pandemic (H1N1) 2009 could result in reassortant viruses that may acquire new characteristics of transmission, virulence, and oseltamivir susceptibility. Results from oseltamivir-sensitivity testing on viral culture suggested the possibility of co-infections with oseltamivir-resistant (seasonal A [H1N1]) and -susceptible (pandemic [H1N1] 2009) viruses.     

Prevention of influenza virus shedding and protection from lethal H1N1 challenge using a consensus 2009 H1N1 HA and NA adenovirus vector vaccine

Vaccines against emerging pathogens such as the 2009 H1N1 pandemic virus can benefit from current technologies such as rapid genomic sequencing to construct the most biologically relevant vaccine. A novel platform (Ad5 [E1-, E2b-]) has been utilized to induce immune responses to various antigenic targets. We employed this vector platform to express hemagglutinin (HA) and neuraminidase (NA) genes from 2009 H1N1 pandemic viruses. Inserts were consensuses sequences designed from viral isolate sequences and the vaccine was rapidly constructed and produced. Vaccination induced H1N1 immune responses in mice, which afforded protection from lethal virus challenge. In ferrets, vaccination protected from disease development and significantly reduced viral titers in nasal washes. H1N1 cell mediated immunity as well as antibody induction correlated with the prevention of disease symptoms and reduction of virus replication. The Ad5 [E1-, E2b-] should be evaluated for the rapid development of effective vaccines against infectious diseases.     

Serologic status for pandemic (H1N1) 2009 virus, Taiwan

We studied preexisting immunity to pandemic (H1N1) 2009 virus in persons in Taiwan. A total of 18 (36%) of 50 elderly adults in Taiwan born before 1935 had protective antibodies against currently circulating pandemic (H1N1) 2009 virus. Seasonal influenza vaccines induced antibodies that did not protect against pandemic (H1N1) 2009 virus.     

Outbreaks of pandemic (H1N1) 2009 and seasonal influenza A (H3N2) on cruise ship

To determine the extent and pattern of influenza transmission and effectiveness of containment measures, we investigated dual outbreaks of pandemic (H1N1) 2009 and influenza A (H3N2) that had occurred on a cruise ship in May 2009. Of 1,970 passengers and 734 crew members, 82 (3.0%) were infected with pandemic (H1N1) 2009 virus, 98 (3.6%) with influenza A (H3N2) virus, and 2 (0.1%) with both. Among 45 children who visited the ship's childcare center, infection rate for pandemic (H1N1) 2009 was higher than that for influenza A (H3N2) viruses. Disembarked passengers reported a high level of compliance with isolation and quarantine recommendations. We found 4 subsequent cases epidemiologically linked to passengers but no evidence of sustained transmission to the community or passengers on the next cruise. Among this population of generally healthy passengers, children seemed more susceptible to pandemic (H1N1) 2009 than to influenza (H3N2) viruses. Intensive disease control measures successfully contained these outbreaks.     

Influenza A Pandemic (H1N1) 2009 Virus Infection in Domestic Cat

Influenza A pandemic (H1N1) 2009 virus continues to rapidly spread worldwide. In 2009, pandemic (H1N1) 2009 infection in a domestic cat from Iowa was diagnosed by a novel PCR assay that distinguishes between Eurasian and North American pandemic (H1N1) 2009 virus matrix genes. Human-to-cat transmission is presumed.     

Monitoring and characterization of oseltamivir-resistant pandemic (H1N1) 2009 virus, Japan, 2009-2010

To monitor and characterize oseltamivir-resistant (OR) pandemic (H1N1) 2009 virus with the H275Y mutation, we analyzed 4,307 clinical specimens from Japan by neuraminidase (NA) sequencing or inhibition assay; 61 OR pandemic (H1N1) 2009 viruses were detected. NA inhibition assay and M2 sequencing indicated that OR pandemic (H1N1) 2009 virus was resistant to M2 inhibitors, but sensitive to zanamivir. Full-genome sequencing showed OR and oseltamivir-sensitive (OS) viruses had high sequence similarity, indicating that domestic OR virus was derived from OS pandemic (H1N1) 2009 virus. Hemagglutination inhibition test demonstrated that OR and OS pandemic (H1N1) 2009 viruses were antigenically similar to the A/California/7/2009 vaccine strain. Of 61 case-patients with OR viruses, 45 received oseltamivir as treatment, and 10 received it as prophylaxis, which suggests that most cases emerged sporadically from OS pandemic (H1N1) 2009, due to selective pressure. No evidence of sustained spread of OR pandemic (H1N1) 2009 was found in Japan; however, 2 suspected incidents of human-to-human transmission were reported.     

Pandemic (H1N1) 2009 Virus on Commercial Swine Farm, Thailand

A swine influenza outbreak occurred on a commercial pig farm in Thailand. Outbreak investigation indicated that pigs were co-infected with pandemic (H1N1) 2009 virus and seasonal influenza (H1N1) viruses. No evidence of gene reassortment or pig-to-human transmission of pandemic (H1N1) 2009 virus was found during the outbreak.     

Risk Factors for Pandemic (H1N1) 2009 Virus Seroconversion among Hospital Staff, Singapore

We describe incidence and risk factors for pandemic (H1N1) 2009 virus infection in healthcare personnel during the June–September 2009 epidemic in Singapore. Personnel contributed 3 serologic samples during June–October 2009, with seroconversion defined as a >4-fold increase in hemagglutination inhibition titers to pandemic (H1N1) 2009. Of 531 participants, 35 showed evidence of seroconversion. Seroconversion rates were highest in nurses (28/290) and lowest in allied health staff (2/116). Significant risk factors on multivariate analysis were being a nurse (adjusted odds ratio [aOR] 4.5, 95% confidence interval [CI] 1.0–19.6) and working in pandemic (H1N1) 2009 isolation wards (aOR 4.5, 95% CI 1.3–15.6). Contact with pandemic (H1N1) 2009–infected colleagues (aOR 2.5, 95% CI 0.9–6.6) and larger household size (aOR 1.2, 95% CI 1.0–1.4) were of borderline significance. Our study suggests that seroconversion was associated with occupational and nonoccupational risk factors.     

四川省成都市甲型H1N1流感血清学调查结果分析

目的了解成都市人群甲型H1N1流感感染现状。方法按照国家方案采集不同年龄组人群血清标本,用血凝抑制(HI)试验方法进行抗体检测,HI抗体滴度≥1∶40判为阳性。结果成都市甲型H1N1流感阳性率8.85%(108/1221);13～17岁组阳性率最高(13.85%,P0.05);男女性阳性率差异无统计学意义;就诊人群阳性率低于一般人群,但差异无统计学意义。结论成都市发生了甲型H1N1流感社区流行,但在人群中的自然感染未形成有效免疫屏障,甲型H1N1流感疫苗接种仍有必要。     

2009年深圳市龙岗区甲型H1N1流感聚集性疫情分析

目的了解深圳市龙岗区甲型H1N1流感聚集性疫情流行特点。方法通过深圳市龙岗区流感监测网络,收集整理甲型H1N1流感聚集性疫情资料;利用反转录-聚合酶链反应技术检测甲型H1N1流感病毒。结果 2009年共发生甲型H1N1流感聚集性疫情62起,流感样病例811例,总罹患率为6.60%。疫情主要发生在9-11月（占88.71%）,学校累计报告57起,占91.94%。各起疫情平均报告时间为1～7d,中位数为3d。甲型H1N1流感疫情持续时间为2～23 d,中位数为7 d;季节性流感疫情持续时间为2～15d,中位数为4d;差异有统计学意义（P〈0.05）。2009年流感疫情发生时共采样251份,其中阳性162份,阳性率为64.54%。结论深圳市龙岗区2009年甲型H1N1流感聚集性疫情流行强度高于前三年季节性流感平均水平,9-11月是该区甲型H1N1流感样病例暴发疫情的高发季节,以局部暴发为主要特征,学校是高发场所。加强疾病监测,落实防控措施,积极开展健康教育,及早报告有利于疫情及时控制。     

Immunogenicity and safety of a monovalent vaccine for the 2009 pandemic influenza virus A (H1N1) in children and adolescents

The 2009 pandemic influenza A (H1N1) has caused significant morbidity and mortality around the world. Safety and immunogenicity studies of 2009 pandemic influenza A (H1N1) virus in children and adolescents are limited. In this prospective, open-label study, 2 doses of a monovalent, unadjuvanted, inactivated, split-virus 2009 pandemic influenza virus A (H1N1) vaccine (AdimFlu-S) were administered to 183 healthy children and adolescents aged 1–17 years. Adverse reactions were assessed, and hemagglutination inhibition antibody titers were determined. Three weeks after the first dose, 36.2% of children aged 1–2 years, 52.5% of children aged 3–5 years, 56.7% of children aged 6–9 years, and 90.3% of adolescents aged 10–17 years generated protective antibodies. A second vaccination given 3 weeks later induced protective antibodies in 89.4% of all age groups. No severe adverse effects were found 6 weeks after vaccination.     

北京市人群甲型H1N1流感血清流行病学调查

目的 了解和掌握北京市人群对甲型H1N1流感的免疫水平.方法 在2009年11月27日至12月23日从医院患者(排除感染科和呼吸科)、血液中心志愿者和体检中心健康体检者中随机选取调查对象进行问卷调查,并采集血清标本进行甲型H1N1流感病毒血凝抑制(HI)抗体检测.结果 共选取调查对象856名,其中127名(14.8%)调查对象体内甲型H1N1流感病毒HI抗体为阳性.0～5岁、6～17岁、18～55岁、≥56岁年龄组HI抗体阳性率分别为14.5%、19.4%、17.4℅和8.0%(P=0.009).不同性别HI抗体阳性率差异无统计学意义(P=0.693).人群血清HI抗体年龄加权阳性率为15.8%.多因素logistic回归分析显示,年龄、出现过急性呼吸道症状以及接种甲型H1N1流感疫苗与HI抗体阳性呈显著性相关.结论 北京市已经有超过15%的人群具有甲型H1N1流感保护性抗体,普通人群中已经建立一定的免疫屏障.     

广元市甲型H1N1流感抗体水平调查

目的了解广元市人群甲型H1N1流感病毒感染水平,为评估疫情发展趋势提供信息支持。方法采集不同年龄段的城市和农村人口的血清用血凝抑制实验（HI）方法进行抗体检测,用统计学方法对抗体水平进行分析。结果 2010年共采集754份血清标本,其中甲型H1N1抗体阳性140份,阳性率18.6%,GMT1∶11。不同时间点、不同地区调查对象甲型H1N1抗体水平差异有统计学意义（P〈0.05）,不同性别、不同年龄组之间抗体水平差异无统计学意义（P〉0.05）。多因素logistic回归分析显示,甲型H1N1疫苗接种、调查时间和地区差异与HI抗体阳性呈显著性相关。结论广元市人群中18%以上具有甲型H1N1流感保护抗体,但抗体水平仍然较低,应进一步加强甲型H1N1流感疫苗的宣传和接种。     

Household transmission of Pandemic (H1N1) 2009 Virus, Taiwan

During August-November 2009, to investigate disease transmission within households in Taiwan, we recruited 87 pandemic (H1N1) 2009 patients and their household members. Overall, pandemic (H1N1) 2009 virus was transmitted to 60 (27%) of 223 household contacts. Transmission was 4× higher to children than to adults (61% vs. 15%; p<0.001).     

Genomic Signatures of Influenza A Pandemic (H1N1) 2009 Virus

Adaptive mutations that have contributed to the emergence of influenza A pandemic (H1N1) 2009 virus, which can replicate and transmit among humans, remain unknown. We conducted a large-scale scanning of influenza protein sequences and identified amino acid–conserving positions that are specific to host species, called signatures. Of 47 signatures that separate avian viruses from human viruses by their nonglycoproteins, 8 were human-like in the pandemic (H1N1) 2009 virus. Close examination of their amino acid residues in the recent ancestral swine viruses of pandemic (H1N1) 2009 virus showed that 7 had already transitioned to human-like residues and only PA 356 retained an avian-like K; in pandemic (H1N1) 2009 virus, this residue changed into a human-like R. Signatures that separate swine viruses from human viruses were also present. Continuous monitoring of these signatures in nonhuman species will help with influenza surveillance and with evaluation of the likelihood of further adaptation to humans.     

Experimental pandemic (H1N1) 2009 virus infection of cats

To demonstrate that pandemic (H1N1) 2009 virus may cause respiratory disease in cats, we intratracheally infected cats. Diffuse alveolar damage developed. Seroconversion of sentinel cats indicated cat-to-cat virus transmission. Unlike in cats infected with highly pathogenic avian influenza virus (H5N1), extrarespiratory lesions did not develop in cats infected with pandemic (H1N1) 2009 virus.     

Comparison of Pandemic (H1N1) 2009 and Seasonal Influenza, Western Australia, 2009

We compared confirmed pandemic (H1N1) 2009 influenza and seasonal influenza diagnosed in Western Australia during the 2009 influenza season. From 3,178 eligible reports, 984 pandemic and 356 seasonal influenza patients were selected; 871 (88.5%) and 288 (80.9%) were interviewed, respectively. Patients in both groups reported a median of 6 of 11 symptoms; the difference between groups in the proportion reporting any given symptom was <10%. Fewer than half the patients in both groups had >1 underlying condition, and only diabetes was associated with pandemic (H1N1) 2009 influenza (odds ratio [OR] 1.9, 95% confidence interval [CI] 1.1–3.5). A total of 129 (14.8%) persons with pandemic (H1N1) 2009 and 36 (12.5%) persons with seasonal influenza were hospitalized (p = 0.22). After controlling for age, we found that patient hospitalization was associated with pandemic (H1N1) 2009 influenza (OR 1.5; 95% CI 1.1–2.1). Contemporaneous pandemic and seasonal influenza infections were substantially similar in terms of patients’ symptoms, risk factors, and proportion hospitalized.     

Serologic survey of pandemic influenza A (H1N1 2009) in Beijing, China

Objective

To examine the frequency and distribution of antibodies against pandemic influenza A (H1N1 2009) [H1N1] in populations in Beijing and elucidate influencing factors.

Methods

In January 2010, a randomized serologic survey of pandemic influenza A (H1N1 2009) was carried out. Six districts that were randomly selected with a total of 4601 participants involved in the survey have their antibody level tested by hemagglutination inhibition assay.

Results

Among the 4601 participants, the overall seropositive rate for pandemic influenza A (H1N1 2009) antibodies was 31.7%. The seropositivity prevalence in participants who received the pandemic H1N1 vaccination was 60.9%. Only 53.1% of the pandemic influenza A (H1N1 2009) seropositive individuals who had not received the vaccination experienced respiratory tract infection symptoms. Multivariate logistic regression revealed that factors such as age, occupation, dwelling type, whether the participant's family included students in school, and the vaccination history with pandemic influenza A (H1N1 2009) were associated with antibody titers (p < 0.05).

Conclusions

Our data indicated that almost 30.0% of the residents had appropriate antibody titers against pandemic influenza A (H1N1 2009) in Beijing, and these titers may provide an immune barrier.