The therapeutic effects of sodium cromoglycate against influenza A virus H5N1 in mice

Objectives

To identify the protective role of sodium cromoglycate in mice during influenza virus infection.

Design

H5N1 virus‐infected mice were treated with the mast cell stabilizer sodium cromoglycate (SCG) to investigate its therapeutic effect.

Sample

The nose, trachea and lungs from mice were collected.

Main outcome measures

Virus replication and host responses were determined by plaque assay, quantitative PCR, immunohistochemistry, and histology.

Results

SCG‐treated mice survived better than did PBS‐treated mice after H5N1 virus infection. Mild pathological changes with fewer inflammatory cell infiltration and fewer virus antigens were observed in the nose, trachea, and lungs of SCG‐treated mice on days 3 and 5 post‐infection. However, no significant changes in viral load in the lungs were detected between SCG‐ and PBS‐treated mice. Furthermore, significantly decreased expression of interleukin‐6, tumor necrosis factor‐a, Toll‐like receptor 3, and TIR‐domain‐containing adapter‐inducing interferon‐b was detected in the lungs of SCG‐treated mice, and no higher expression of interferon‐c was detected.

Conclusion

These results suggest that SCG has therapeutic roles in H5N1 virus‐infected mice by alleviating the inflammatory response rather than inhibition of viral replication in the lungs.     

Effect of passive immunization on immunogenicity and protective efficacy of vaccination against a Mexican low‐pathogenic avian H5N2 influenza virus

Background

Despite the use of vaccines, low‐pathogenic (LP) H5N2 influenza viruses have continued to circulate and evolve in chickens in Mexico since 1993, giving rise to multiple genetic variants. Antigenic drift is partially responsible for the failure to control H5N2 influenza by vaccination; the contribution of maternal antibodies to this problem has received less attention.

Methods

We investigated the effect of different antisera on the efficacy of vaccination and whether booster doses of vaccine can impact immune suppression.

Results

While single doses of inactivated oil emulsion vaccine to currently circulating H5N2 influenza viruses provide partial protection from homologous challenge, chickens that receive high‐titer homologous antisera intraperitoneally before vaccination showed effects ranging from added protection to immunosuppression. Post‐infection antisera were less immunosuppressive than antisera obtained from field‐vaccinated chickens. Homologous, post‐infection chicken antisera provided initial protection from virus challenge, but reduced the induction of detectable antibody responses. Homologous antisera from field‐vaccinated chickens were markedly immunosuppressive, annulling the efficacy of the vaccine and leaving the chickens as susceptible to infection as non‐vaccinated birds. Booster doses of vaccine reduced the immunosuppressive effects of the administered sera.

Conclusion

Vaccine efficacy against LP H5N2 in Mexico can be severely reduced by maternal antibodies. Source‐dependent antisera effects offer the possibility of further elucidation of the immunosuppressive components involved.     

Emergence of H3N2pM‐like and novel reassortant H3N1 swine viruses possessing segments derived from the A (H1N1)pdm09 influenza virus,Korea

Background

Human‐to‐swine transmission of the pandemic H1N1 2009 [A(H1N1)pdm09] virus in pig populations resulted in reassortment events with endemic swine influenza viruses worldwide.

Objective

We investigated whether A(H1N1)pdm09‐derived reassortant viruses are present in South Korea and sought to determine the pathogenic potential of the novel swine viruses.

Methods

Pig lung tissues were collected from commercially slaughtered pigs. Isolated swine influenza viruses were genetically analyzed and characterized in vitro and in vivo.

Results

We identified reassortant H3N2 (H3N2pM‐like) and H3N1 swine viruses containing A(H1N1)pdm09‐like segments in Korean pigs that are genetically closely related to strains recently detected in pigs and humans in North America. Although the H3N2pM‐like and novel H3N1 reassortants demonstrated efficient replication in mice and ferrets, all the H3N1 strains exhibited growth advantage over the representative H3N2pM‐like virus in human airway cells. Interestingly, A/swine/Korea/CY02‐07/2012(H3N1) and A/swine/Korea/CY03‐13/2012(H3N1) reassortants were more readily transmitted to respiratory‐droplet‐contact ferrets compared with the H3N2pM‐like (A/swine/Korea/CY02‐10/2012) isolate. Furthermore, serologic evaluation showed poor antigenicity to contemporary reference human seasonal H3N2 vaccine strains.

Conclusions

We report here for the first time the isolation of H3N2pM‐like viruses outside North America and of novel reassortant swine H3N1 viruses with A(H1N1)pdm09‐derived genes. Apart from further complicating the genetic diversity of influenza A viruses circulating in domestic pigs, our data also indicate that these strains could potentially pose threat to public health asserting the need for continuous virus monitoring in these ecologically important hosts.     

Inactivated influenza virus vaccine is efficient and reduces IL‐4 and IL‐6 in allergic asthma mice

Background

Allergic asthma is a globally respiratory inflammatory disease. Influenza virus is a respiratory pathogen that causes yearly epidemics and results in high rates of morbidity and mortality. Patients with allergic asthma had a more severe symptom and a higher mortality when they were infected with influenza virus. Hence, influenza vaccination is recommended for patients with asthma.

Objectives

We evaluated the efficacy and effects of influenza vaccination on allergic asthma in a mouse model.

Methods

Ovalbumin‐immunized mice were inoculated with inactivated influenza virus A/Puerto Rico/8/34 (PR8) as vaccines and morbidity or mortality and allergic asthma features of these mice were analyzed.

Results

Mice inoculated with inactivated PR8 induced high levels of anti‐PR8 IgG2a and upregulation of Toll‐like receptor (TLR) 7. Vaccinated allergic mice were healthy when they were challenged with live influenza virus while none of non‐vaccinated allergic mice survived. Furthermore, inactivated influenza virus vaccine induced neither extra airway inflammation nor asthma features such as IgE, airway hyper‐reactivity, and eosinophilia in allergic mice. Particularly, decreased frequency of immune cell infiltrated airways and Th2 cytokines IL‐4 and IL‐6 production in the bronchoalveolar lavage fluid were noted in vaccinated allergic mice. These results suggested that inactivated influenza virus vaccine is efficient to protect allergic mice from further influenza infection, and it does not exacerbate but reduces IL‐4 and IL‐6 of allergic asthma.

Conclusion

Influenza vaccination is essential and efficient for allergic subjects to protect influenza virus infection.     

Characterization of neuraminidase inhibitor‐resistant influenza A(H1N1)pdm09 viruses isolated in four seasons during pandemic and post‐pandemic periods in Japan

Background/Objectives

Japan has the highest frequency of neuraminidase (NA) inhibitor use against influenza in the world. Therefore, Japan could be at high risk of the emergence and spread of NA inhibitor‐resistant viruses. The aim of this study was to monitor the emergence of NA inhibitor‐resistant viruses and the possibility of human‐to‐human transmission during four influenza seasons in Japan.

Methods

To monitor antiviral‐resistant A(H1N1)pdm09 viruses, we examined viruses isolated in four seasons from the 2008–2009 season through the 2011–2012 season in Japan by allelic discrimination, NA gene sequencing, and NA inhibitor susceptibility.

Results

We found that 157 (1·3%) of 12 026 A(H1N1)pdm09 isolates possessed an H275Y substitution in the NA protein that confers about 400‐ and 140‐fold decreased susceptibility to oseltamivir and peramivir, respectively, compared with 275H wild‐type viruses. The detection rate of resistant viruses increased from 1·0% during the pandemic period to 2·0% during the post‐pandemic period. The highest detection rate of the resistant viruses was found in patients who were 0–9 years old. Furthermore, among the cases with resistant viruses, the percentage of no known exposure to antiviral drugs increased from 16% during the pandemic period to 44% during the post‐pandemic period, implying that suspected human‐to‐human transmission of the resistant viruses gradually increased in the post‐pandemic period.

Conclusions

A(H1N1)pdm09 viruses resistant to oseltamivir and peramivir were sporadically detected in Japan, but they did not spread throughout the community. No viruses resistant to zanamivir and laninamivir were detected.     

Infection of swine ex vivo tissues with avian viruses including H7N9 and correlation with glycomic analysis

Objectives

Swine have been regarded as intermediate hosts in the spread of influenza from birds to humans but studies of the sialylated glycans that comprise their respiratory tract have not been extensively studied in the past. This study analyzed the sialylated N‐glycan and O‐glycan profile of swine trachea and lung and correlated this with ex‐vivo infection of swine explants with avian influenza viruses.

Sample

Lungs and tracheal samples were obtained from normal farm and laboratory raised swine and used for ex vivo infection as well as mass spectrometric analysis. Infection of the ex vivo tissues used high pathogenic and low pathogenic avian viruses including the novel H7N9 virus that emerged in China in early 2013.

Main outcome measures

Assessment of successful replication was determined by TCID50 as well as virus immunohistochemistry. The N‐glycan and O‐glycan profiles were measured by MALDI‐TOF and sialylated linkages were determined by sialidase treatment. Lectin binding histochemistry was also performed on formalin fixed tissue samples with positive binding detected by chromogen staining.

Results

The swine respiratory tract glycans differed from the human respiratory tact glycans in two main areas. There was a greater abundance of Gal‐α‐Gal linkages resulting in a relative decrease in sialylated glycans. The swine respiratory tract also had a greater proportion of glycans containing Neu5Gc and Siaα2‐6 glycans than the human respiratory tract. Infection with avian viruses was confined primarily to lung bronchioles rather than trachea and parenchyma.

Conclusions

In contrast to previous studies we found that there was not as much expression of Siaα2‐3 glycans on the surface of the trachea. Infection of Siaα2‐3 binding avian viruses was restricted to the lower respiratory tract bronchioles. This finding may diminish the ability of the swine to act as an intermediary in the transmission of avian viruses to humans.     

Heterosubtypic cross‐protection induced by whole inactivated influenza virus vaccine in mice: influence of the route of vaccine administration

Background

Development of influenza vaccines capable of inducing broad protection against different virus subtypes is necessary given the ever‐changing viral genetic landscape. Previously, we showed that vaccination with whole inactivated virus (WIV) induces heterosubtypic protection against lethal virus infection in mice. Whole inactivated virus‐induced cross‐protection was found to be mediated primarily by flu‐specific CD8+ T cells.

Objectives

As it has been demonstrated that the route of vaccine administration strongly influences both the quantity and quality of vaccine‐induced immunity, in this study, we determined which route of WIV administration induces optimal heterosubtypic cross‐protection.

Methods

We compared the magnitude of the immune response and heterosubtypic protection against lethal A/PR/8/34 (H1N1) infection after subcutaneous (SC), intramuscular (IM), and intranasal (IN) vaccination with A/NIBRG‐14 (H5N1) WIV.

Results

Subcutaneous and IM administration was superior to IN administration of influenza WIV in terms of flu‐specific CD8+ T‐cell induction and protection of mice against lethal heterosubtypic challenge. Surprisingly, despite the very low flu‐specific CD8+ T‐cell responses detected in IN‐vaccinated mice, these animals were partially protected, most likely due to cross‐reactive IgA antibodies.

Conclusion

The results of this study show that the magnitude of WIV‐induced flu‐specific CD8+ T‐cell activity depends on the applied vaccination route. We conclude that parenteral administration of WIV vaccine, in particular IM injection, is superior to IN vaccine delivery for the induction of heterosubtypic cross‐protection and generally appears to elicit stronger immune responses than mucosal vaccination with WIV.     

Transmission dynamics of pandemic influenza A(H1N1)pdm09 virus in humans and swine in backyard farms in Tumbes,Peru

Objectives

We aimed to determine the frequency of pH1N1 transmission between humans and swine on backyard farms in Tumbes, Peru.

Design

Two‐year serial cross‐sectional study comprising four sampling periods: March 2009 (pre‐pandemic), October 2009 (peak of the pandemic in Peru), April 2010 (1st post‐pandemic period), and October 2011 (2nd post‐pandemic period).

Sample

Backyard swine serum, tracheal swabs, and lung sample were collected during each sampling period.

Main outcome measures

We assessed current and past pH1N1 infection in swine through serological testing, virus culture, and RT‐PCR and compared the results with human incidence data from a population‐based active surveillance cohort study in Peru.

Results

Among 1303 swine sampled, the antibody prevalence to pH1N1 was 0% pre‐pandemic, 8% at the peak of the human pandemic (October 2009), and 24% in April 2010 and 1% in October 2011 (post‐pandemic sampling periods). Trends in swine seropositivity paralleled those seen in humans in Tumbes. The pH1N1 virus was isolated from three pigs during the peak of the pandemic. Phylogenetic analysis revealed that these viruses likely represent two separate human‐to‐swine transmission events in backyard farm settings.

Conclusions

Our findings suggest that human‐to‐swine pH1N1 transmission occurred during the pandemic among backyard farms in Peru, emphasizing the importance of interspecies transmission in backyard pig populations. Continued surveillance for influenza viruses in backyard farms is warranted.     

Distribution of influenza and other acute respiratory viruses during the first year after the 2009–2010 influenza pandemic in the English‐ and Dutch‐speaking Caribbean countries

Background

Limited specimen collection and testing for influenza occurred in the English and Dutch‐speaking Caribbean countries prior to the 2009/2010 influenza pandemic. Caribbean Epidemiology Centre (CAREC) member countries rapidly mobilized to collect specimens during the pandemic and a vast majority of confirmed cases during the pandemic period were influenza A(H1N1)pdm09.

Objectives

To describe the aetiology and distribution of acute respiratory illness (ARI) among laboratory confirmed cases during the first year after the 2009/2010 influenza pandemic in the English‐ and Dutch‐speaking Caribbean.

Results

In total, 774 specimens were tested and 394 (52.7%) cases had positive laboratory confirmation. Respiratory syncytial virus (RSV) (28.4%) and influenza A(H3N2) (23.1%) were most frequently detected. RSV activity peaked in July 2011 while influenza A(H3N2) peaked in October 2010. Influenza was responsible for illness in greater numbers in persons 15–64 years while RSV was seen in primarily in children <5 years and adults >65 years. Other agents confirmed include rhinovirus (12.9%), influenza B (10.9%) and influenza A(H1N1)pdm09 (9.4%).

Conclusions

RSV and influenza A(H3N2) were the most common viruses identified during the first year after the influenza A(H1N1)pdm09 pandemic. Influenza was detected every month with peak activity corresponding to that typically seen in North America (October to March). In order to determine the seasonality of influenza and RSV, laboratory data from subsequent years and increased specimen submission is needed.     

Community knowledge,behaviours and attitudes about the 2009 H1N1 Influenza pandemic: a systematic review

Background

Effectiveness of pandemic plans and community compliance was extensively researched following the H1N1 pandemic. This systematic review examined community response studies to determine whether behavioural responses to the pandemic were related to level of knowledge about the pandemic, perceived severity of the pandemic and level of concern about the pandemic.

Methods

Literature databases were searched from March 2009 to August 2011 and included cross‐sectional or repeated population surveys undertaken during or following the H1N1 pandemic which reported on community response to the pandemic. Studies using population subgroups and other respiratory diseases were excluded, as were mathematical modelling and qualitative studies.

Results

Nineteen unique studies were included. Fourteen reported pandemic knowledge, 14 reported levels of concern and risk perception and 18 reported pandemic behaviours. Awareness of the pandemic was high, and knowledge was moderate. Levels of concern and risk were low moderate and precautionary behavioural actions lower than intentions. The most commonly reported factors influencing adopting recommended behaviours were increased risk perception and older age, increased pandemic knowledge and being female.

Conclusions

Important implications for future pandemic planning were identified. A remarkable lack of intercountry variability in responses existed; however, differences between populations within a single country suggest one‐size‐fits‐all plans may be ineffective. Secondly, differences between reported precautionary intentions and preventive behaviours undertaken may be related to people''s perceived risk of infection.     

A novel approach for preparation of the antisera reagent for potency determination of inactivated H7N9 influenza vaccines

Background

The potency of inactivated influenza vaccines is determined using a single‐radial immunodiffusion (SRID) assay and requires standardized reagents consisting of a Reference Antigen and an influenza strain‐specific antiserum. Timely availability of reagents is a critical step in influenza vaccine production, and the need for backup approaches for reagent preparation is an important component of pandemic preparedness.

Objectives

When novel H7N9 viruses emerged in China in 2013, candidate inactivated H7N9 influenza vaccines were developed for evaluation in clinical trials, and reagents were needed to measure vaccine potency.

Methods

We previously described an alternative approach for generating strain‐specific potency antisera, utilizing modified vaccinia virus Ankara vectors to produce influenza hemagglutinin (HA)‐containing virus‐like particles (VLPs) for immunization. Vector‐produced HA antigen is not dependent upon the success of the traditional bromelain‐digestion and HA purification.

Results

Antiserum for H7N9 vaccines, produced after immunization of sheep with preparations of bromelain‐HA (br‐HA), was not optimal for the SRID assay, and the supply of antiserum was limited. However, antiserum obtained from sheep boosted with VLPs containing H7 HA greatly improved the ring quality in the SRID assay. Importantly, this antiserum worked well with both egg‐ and cell‐derived antigen and was distributed to vaccine manufacturers.

Conclusions

Utilizing a previously developed approach for preparing vaccine potency antiserum, we have addressed a major bottleneck encountered in preparation of H7N9 vaccine reagents. The combination of br‐HA and mammalian VLPs for sequential immunization represents the first use of an alternative approach for producing an influenza vaccine potency antiserum.     

Unusually high impact of influenza B during the early 2012–2013 influenza season in Wales – epidemiology and clinical analysis of the first 100 cases

Background

Influenza B is often regarded as the milder form of the disease. The early 2012–2013 season in Wales saw the highest rate of influenza B‐associated primary care consultations since 1994–1995 and considerable hospitalisations.

Objectives

This report summarises features of the first 100 confirmed cases during 2012–2013 in Wales.

Methods

Case information was sourced from routine laboratory testing and virological surveillance.

Results and conclusions

Influenza B (Yamagata lineage) viruses dominated, mainly affecting younger adults, admission to critical care was unexpectedly common. Low vaccine uptake amongst at‐risk patients may have contributed to the burden of influenza in secondary care in Wales.     

The impact of influenza and respiratory syncytial virus on hospitalizations for lower respiratory tract infections in young children: Slovenia, 2006–2011

Background

Influenza and respiratory syncytial viruses (RSV) are important viral pathogens in childhood.

Objectives

Our aim was to estimate the effect of influenza and RSV on excess hospitalizations for acute lower respiratory tract infections (ALRTI) in children aged ≤5.

Methods

Retrospective, population‐based study was performed for five seasons (2006–2011). Slovenian national hospital discharge data and surveillance data were used to estimate the effect of influenza and/or RSV on ALRTI hospitalizations (acute bronchiolitis, pneumonia, and acute bronchitis) using rate difference method.

Results

An excess was observed in average weekly ALRTI hospitalizations per 100 000 among children aged ≤5 in all five seasons during influenza and/or RSV active period. During three seasons, there was higher excess in ALRTI hospitalizations in the period when influenza/RSV cocirculated compared with the RSV period. In pandemic season (2009/2010), the only one without influenza/RSV overlap, excess hospitalization was higher in RSV period. The highest excess of hospitalizations was found among the youngest children (0‐5 months old). In all five seasons, acute bronchiolitis was the most common ALRTI recorded in hospitalized young children.

Conclusions

Respiratory syncytial viruses was leading viral pathogen associated with ALRTI hospitalizations in children aged ≤5. The cocirculation of influenza virus increased the burden of ALRTI hospitalizations especially in seasons with A(H3) predominance.     

Divergent seasonal patterns of influenza types A and B across latitude gradient in Tropical Asia

Introduction

Influenza circulation in tropics and subtropics reveals a complex seasonal pattern with year‐round circulation in some areas and biannual peaks in others.

Methods

We analyzed influenza surveillance data from nine countries around southern and southeastern Asia spanning latitudinal gradient from equatorial to temperate zones to further characterize influenza type‐specific seasonality in the region. We calculated proportion of positives by month out of positives during that year and adjust for variation in samples tested and positivity in these countries.

Results

Influenza A epidemics were identified between November and March during winters in areas lying above 30°N latitude, during monsoon months of June–November in areas between 10° and 30°N latitude, and no specific seasonality for influenza A virus circulation in areas lying closer to the equator. Influenza B circulation coincided with influenza A circulation in areas lying above 30°N latitude; however, in areas south of 30°N Asia, influenza B circulated year round at 3–8% of annual influenza B positives during most months with less pronounced peaks during post‐monsoon period.

Conclusion

Even though influenza B circulates round the year in most areas of the tropical regions of southern and southeastern Asia, the most appropriate time for influenza vaccination using the most recent WHO recommended vaccine would be prior to the monsoon season conferring protection against influenza A and B peaks.     

Improving the representativeness of influenza viruses shared within the WHO Global Influenza Surveillance and Response System

Background

Sharing influenza viruses within the WHO Global Influenza Surveillance and Response System is crucial for monitoring evolution of influenza viruses.

Objectives

Analysis of timeliness and geographic representativeness of viruses shared by National Influenza Centres (NICs) in the WHO European Region with the London WHO Collaborating Centre for Reference and Research on Influenza for the Northern Hemisphere''s 2010–2011 and 2011–2012 influenza seasons.

Materials and methods

Data from NICs on influenza‐positive specimens shared with WHO CC London for the above‐mentioned influenza seasons were analyzed for timeliness of sharing with respect to the February deadline (31 January) for inclusion in the WHO consultations on the composition of influenza virus vaccines for the Northern Hemisphere and geographic representativeness.

Results

The 2010–2011 and 2011–2012 seasons were different in terms of the seasonal pattern, the timing of the epidemic, and the dominant virus. Consistent patterns of virus sharing across the seasons were observed. Approximately half the viruses collected before the deadline were not shared within the deadline; the average delay between date of specimen collection and shipment receipt was 3 and 1·5 months for the first and second season, respectively.

Conclusion

A baseline was provided for future work on enhancement of specimen sharing in the WHO European Region and improving the vaccine virus selection process. Greater insight into virus selection criteria applied by countries and the causes of delays in shipment are needed to understand the representativeness of viruses shared and to assess the importance of this for vaccine strain selection.     

Mortality burden of the 2009‐10 influenza pandemic in the United States: improving the timeliness of influenza severity estimates using inpatient mortality records

Background

Delays in the release of national vital statistics hinder timely assessment of influenza severity, especially during pandemics. Inpatient mortality records could provide timelier estimates of influenza‐associated mortality.

Methods

We compiled weekly age‐specific deaths for various causes from US State Inpatient Databases (1990–2010) and national vital statistics (1990–2009). We calculated influenza‐attributable excess deaths by season based on Poisson regression models driven by indicators of respiratory virus activity, seasonality, and temporal trends.

Results

Extrapolations of excess mortality from inpatient data fell within 11% and 17% of vital statistics estimates for pandemic and seasonal influenza, respectively, with high year‐to‐year correlation (Spearman''s rho = 0·87–0·90, P < 0·001, n = 19). We attribute 14 800 excess respiratory and cardiac deaths (95% CI: 10 000–19 650) to pandemic influenza activity during April 2009–April 2010, 79% of which occurred in people under 65 years.

Conclusions

Modeling inpatient mortality records provides useful estimates of influenza severity in advance of national vital statistics release, capturing both the magnitude and the age distribution of pandemic and epidemic deaths. We provide the first age‐ and cause‐specific estimates of the 2009 pandemic mortality burden using traditional ‘excess mortality’ methods, confirming the unusual burden of this virus in young populations. Our inpatient‐based approach could help monitor mortality trends in other infectious diseases.     

Epidemiological and virological findings during multiple outbreaks of equine influenza in South America in 2012

Background

In 2012, equine influenza (EI) virus was confirmed as the cause of outbreaks of respiratory disease in horses throughout South America. In Uruguay and Argentina, hundreds of vaccinated thoroughbred horses in training and racing facilities were clinically affected.

Objective

To characterise the EI viruses detected during the outbreak in Uruguay and Argentina.

Methods

Virus was detected in nasopharyngeal swabs by a pan‐reactive influenza type A real‐time RT‐PCR. The nucleotide sequence of the HA1 gene was determined and analysed phylogenetically using mega 5 software. Amino acid sequences alignments were constructed and virus was antigenically characterised with specific ferret antisera. Paired serum samples were tested by haemagglutination inhibition and single radial haemolysis.

Results

The diagnosis of EIV was confirmed by real‐time RT‐PCR, virus isolation and serological testing. The phylogenetic analysis of HA1 gene sequences of 18 EI viruses indicated that all of them belong to clade 1 of the Florida sublineage of the American lineage and are closely related to viruses isolated in the United States in 2012. The HA1 of viruses identified in horses in racing facilities in Maroñas, Uruguay, and in Palermo, Argentina, displayed 100% amino acid sequence identity and were identical to that of a virus isolated in Dubai in 2012, from vaccinated endurance horses recently imported from Uruguay.

Conclusions

The surveillance data reported illustrate the international spread of EI viruses and support the recommendations of the OIE expert surveillance panel to include viruses of the Florida sublineage in vaccines.