Laboratory diagnosis of influenza virus infection

Establishment of a Pseudovirus Platform for Neuraminidase Inhibiting Antibody Analysis

Neuraminidase (NA)-based immunity to influenza can be useful for protecting against novel antigenic variants. To develop safe and effective tools to assess NA-based immunity, we generated a baculovirus-based pseudotyped virus, N1-Bac, that expresses the full-length NA of the influenza A/California/07/2009 (H1N1)pdm09 strain. We evaluated the level of NA-inhibiting (NI) antibodies in the paired blood sera of influenza patients by means of an enzyme-linked lectin assay (ELLA) using the influenza virus or N1-Bac. Additionally, we evaluated the level of NA antibodies by means of the enzyme-linked immunosorbent assay (ELISA) with an N1-expressing Sf21 culture. We detected a strong correlation between our results from using the influenza virus and NA-Bac pseudoviruses to detect NI antibodies and a medium-strong correlation between NI antibodies and NA antibodies determined by an N1-cell ELISA, indicating that baculovirus-based platforms can be successfully used to evaluate NI or NA antibodies. Furthermore, animal experiments showed that immunization with N1-Bac protected against infection with a drift variant of the A/H1N1pdm09 influenza virus. Our results demonstrate that recombinant baculovirus can be an effective influenza pseudotype to evaluate influenza serologic immunity and protect against influenza virus infection.

History and current trends in influenza virus infections with special reference to Sri Lanka

The World Health Organization (WHO) estimates that approximately one billion people are infected and up to 500,000 people die from influenza each year in the world. Influenza is considered to be the greatest killer of the human populations, due to the 1918 Spanish flu, which killed millions around the world. Despite the effective treatment available against influenza, it still contributes to significant morbidity and mortality. Currently circulating influenza strains in humans include influenza A (H1N1)pdm09, influenza A (H3N2) and influenza B viruses, (B/Victoria and B/Yamagata). Influenza has been prevalent in Sri Lanka from 1969, since then it continued to cause morbidity and mortality in children and adults. The current global influenza surveillance network monitors the global influenza activity through WHO collaborating centres. The Medical Research Institute monitors and diagnoses influenza cases in the country as part of the WHO network laboratories. Vaccinations to high risk groups and antiviral therapy for the successful prevention of influenza have been practiced in Sri Lanka. This review highlights the impact of influenza on public health in Sri Lanka including the historical aspects, current diagnostic practices and prevention approaches in high risk individuals in the country.

Molecular diagnosis of respiratory viruses

The increasing availability of nucleic acid amplification tests since the 1980s has revolutionised our understanding of the pathogenesis, epidemiology, clinical and laboratory aspects of known and novel viral respiratory pathogens. High-throughput, multiplex polymerase chain reaction is the most commonly used qualitative detection method, but utilisation of newer techniques such as next-generation sequencing will become more common following significant cost reductions. Rapid and readily accessible isothermal amplification platforms have also allowed molecular diagnostics to be used in a ‘point-of-care’ format. This review focuses on the current applications and limitations of molecular diagnosis for respiratory viruses.

Evaluation of the Sofia Influenza A + B fluorescent immunoassay for the rapid diagnosis of influenza A and B

Rapid influenza diagnostic tests (RIDTs) can facilitate the appropriate prescription of antivirals for influenza, obviate the need for unnecessary testing and antibacterial agents and allow the implementation of infection control measures. However, the reported sensitivities and specificities of different RIDTs vary widely in clinical settings, as does assay ability to distinguish between influenza types and subtypes. To evaluate the performance of the Sofia Influenza A + B fluorescent immunoassay (FIA) for the detection of influenza A and B during the 2013 Southern Hemisphere influenza season, a total of 209 consecutive respiratory tract swabs from adult patients with an influenza-like illness were tested by both Sofia Influenza A + B and an in-house real-time, reverse transcription-polymerase chain reaction (RT-PCR) assay. Compared to RT-PCR, the sensitivity and specificity of the Sofia Influenza A + B FIA for detection of influenza A was 72.4% and 98.3%, respectively. Too few influenza B positive samples were available during the study to accurately assess the Sofia's performance for influenza B detection. The sensitivity of Sofia Influenza A + B FIA for both influenza A and B detection correlated with the amount of influenza RNA present in the sample as indicated indirectly by the RT-PCR cycle threshold (Ct ). In conclusion, the Sofia Influenza A + B FIA continues to perform well as a RIDT with the circulating influenza strains of the 2013 Southern Hemisphere influenza season.

Comparing the use of, and considering the need for, lumbar puncture in children with influenza or other respiratory virus infections

BACKGROUND

The clinical presentation of influenza in infancy may be similar to serious bacterial infection and be investigated with invasive procedures like lumbar puncture (LP), despite very limited evidence that influenza occurs concomitantly with bacterial meningitis, perhaps because the diagnosis of influenza is very often not established when the decision to perform LP is being considered.

METHODS

A retrospective medical record review was undertaken in all children presenting to the Children's Hospital at Westmead, Sydney, Australia, in one winter season with laboratory-confirmed influenza or other respiratory virus infections (ORVIs) but excluding respiratory syncytial virus, to compare the use of, and reflect on the need for, the performance of invasive diagnostic procedures, principally LP, but also blood culture, in influenza and non-influenza cases. We also determined the rate of concomitant bacterial meningitis or bacteraemia.

FINDINGS

Of 294 children, 51% had laboratory-confirmed influenza and 49% had ORVIs such as parainfluenza viruses (34%) and adenoviruses (15%). Of those with influenza, 18% had a LP and 71% had a blood culture performed compared with 6·3% and 55·5% in the ORVI group (for both P<0·01). In multivariate analysis, diagnosis of influenza was a strong independent predictor of both LP (P=0·02) and blood culture (P=0·05) being performed, and, in comparison with ORVIs, influenza cases were almost three times more likely to have a LP performed on presentation to hospital. One child with influenza (0·9%) had bacteraemia and none had meningitis.

INTERPRETATION

Children with influenza were more likely to undergo LP on presentation to hospital compared with those presenting with ORVIs. If influenza is confirmed on admission by near-patient testing, clinicians may be reassured and less inclined to perform LP, although if meningitis is clinically suspected, the clinician should act accordingly. We found that the risk of bacterial meningitis and bacteraemia was very low in hospitalised children with influenza and ORVIs. A systematic review should be performed to investigate this across a large number of settings.

Treating and preventing influenza in aged care facilities: a cluster randomised controlled trial

BACKGROUND

Influenza is an important cause of morbidity and mortality for frail older people. Whilst the antiviral drug oseltamivir (a neuraminidase inhibitor) is approved for treatment and prophylaxis of influenza during outbreaks, there have been no trials comparing treatment only (T) versus treatment and prophylaxis (T&P) in Aged Care Facilities (ACFs). Our objective was to compare a policy of T versus T&P for influenza outbreaks in ACFs.

METHODS AND FINDINGS

We performed a cluster randomised controlled trial in 16 ACFs, that followed a policy of either "T"-oseltamivir treatment (75 mg twice a day for 5 days)-or "T&P"-treatment and prophylaxis (75 mg once a day for 10 days) for influenza outbreaks over three years, in addition to enhanced surveillance. The primary outcome measure was the attack rate of influenza. Secondary outcomes measures were deaths, hospitalisation, pneumonia and adverse events. Laboratory testing was performed to identify the viral cause of influenza-like illness (ILI) outbreaks. The study period 30 June 2006 to 23 December 2008 included three southern hemisphere winters. During that time, influenza was confirmed as the cause of nine of the 23 ILI outbreaks that occurred amongst the 16 ACFs. The policy of T&P resulted in a significant reduction in the influenza attack rate amongst residents: 93/255 (36%) in residents in T facilities versus 91/397 (23%) in T&P facilities (p=0.002). We observed a non-significant reduction in staff: 46/216 (21%) in T facilities versus 47/350 (13%) in T&P facilities (p=0.5). There was a significant reduction in mean duration of outbreaks (T=24 days, T&P=11 days, p=0.04). Deaths, hospitalisations and pneumonia were non-significantly reduced in the T&P allocated facilities. Drug adverse events were common but tolerated.

CONCLUSION

Our trial lacked power but these results provide some support for a policy of "treatment and prophylaxis" with oseltamivir in controlling influenza outbreaks in ACFs.

TRIAL REGISTRATION

[corrected] Australian Clinical Trials Registry ACTRN12606000278538.

A novel high-speed droplet-polymerase chain reaction can detect human influenza virus in less than 30 min

BACKGROUND

The polymerase chain reaction (PCR) has been widely used for diagnosis of infection. Rapid detection of influenza virus is useful for therapeutic decisions. We attempted to develop a novel assay by real-time droplet-PCR machine for influenza virus.

METHODS

RNA extracted from nasal swabs or primary swabs pretreated only were used for PCR analyses. We evaluated reaction time, amplification efficiency, sensitivity, and specificity of the novel droplet-PCR.

RESULTS

The reaction time of the novel droplet-PCR was 28 min, whereas that of PCR using the conventional PCR machine was 80 min. The standard curve constructed from the amplification plots by the novel droplet-PCR was: y=-3.6x+42.9; that by PCR using the conventional PCR machine was: y=-3.5x+37.8. The sensitivity and specificity of the novel droplet-PCR were 86.7% and 91.7% for the influenza A and 100.0% and 100.0% for the influenza B, respectively. The novel droplet-PCR provided the specific amplification when using primary swabs without RNA extraction.

CONCLUSIONS

Our novel droplet-PCR markedly reduced the reaction time while showing same reactivity as that by PCR using the conventional PCR machine. Thus, the novel droplet-PCR assay can be used as a rapid assay for detection of influenza virus.

Evaluation of two different swab transport systems in the detection of avian influenza virus excretion from infected Pekin ducks (Anas platyrhynchos)

The role of wild birds in the epidemiology and ecology of influenza A viruses has long been recognised (Alexander, 2007a). As a result of the emergence of a H5N1 highly pathogenic avian influenza (HPAI) virus and the apparent role of wild birds in its spread across Asia, Europe and Africa, avian influenza (AI) wild bird surveillance has been implemented in many countries including, since February 2006, a mandatory programme in the European Union (CEC, 2006a). In the present study the detection of virus excreted from Pekin ducks (Anas platyrhynchos) infected experimentally with A/mallard/England/2126/07 (H3N6) was investigated over a fourteen day period post-infection using cloacal and oropharyngeal swabs, with (wet) and without (dry) viral transport medium which were collected from each duck in alternating order. For influenza A virus matrix gene RNA detection, wet oropharyngeal swabs were significantly more sensitive than dry oropharyngeal on days 4-5 after infection. For cloacal samples, dry swabs were equivalent or superior to wet swabs throughout the study. Although differences in detection between dry and wet swabs were observed, the qualitative bird-level results were unaffected, meaning that the infection status of individual birds was correctly determined.

Clinical features, oseltamivir treatment and outcome in infants aged <12 months with laboratory-confirmed influenza A in 2009

BACKGROUND

Data on the use of oseltamivir in infants is limited. We documented the clinical presentations of infants aged <12 months hospitalized with laboratory-confirmed influenza A in the southern hemisphere winter of 2009 and compared outcomes in relation to oseltamivir therapy.

METHODS

Data were extracted from prospectively collected and collated influenza case reports (June-September 2009) ascertained through Paediatric Active Enhanced Disease Surveillance, an in-patient surveillance system operating at the Children's Hospital at Westmead (CHW), Sydney, NSW, Australia. Nosocomial cases were excluded.

RESULTS

Of 56 infants with definite influenza (35 pandemic H1N1 2009) admitted to the CHW, 20 were treated with oseltamivir. Overall, 12 (60%) of those treated with oseltamivir were aged <6 months. Cough, fever and coryza were the most common clinical features (≥70%). Vomiting was present on admission in 31.4%. All 7 cases presenting with vomiting then given antiviral treatment had reduction of vomiting and the other 13 did not develop vomiting on treatment. There were three infants with hypoxaemia (oxygen saturation ≤93%) on presentation in the treatment group compared with none in the control group (P=0.04). The median duration of hospital stay was the same in both groups (2.5 days).

CONCLUSIONS

The use of oseltamivir was well tolerated in hospitalized infants. Vomiting, one of the widely reported side effects of oseltamivir, was found to be more a presenting symptom of influenza than a side effect of oseltamivir. Based on pulse oximetry, oseltamivir-treated cases may have been more severe on presentation, but there was no significant difference in length of hospital stay.

Subtyping animal influenza virus with general multiplex RT-PCR and Liquichip high throughput (GMPLex)

This study developed a multiplex RT-PCR integrated with luminex technology to rapidly subtype simultaneously multiple influenza viruses. Primers and probes were designed to amplify NS and M genes of influenza A viruses HA gene of H1, H3, H5, H7, H9 subtypes, and NA gene of the N1 and N2 subtypes. Universal super primers were introduced to establish a multiplex RT-PCR (GM RT-PCR). It included three stages of RT-PCR amplification, and then the RT-PCR products were further tested by LiquiChip probe, combined to give an influenza virus (IV) rapid high throughput subtyping test, designated as GMPLex. The IV GMPLex rapid high throughput subtyping test presents the following features: high throughput, able to determine the subtypes of 9 target genes in H1, H3, H5, H7, H9, N1, and N2 subtypes of the influenza A virus at one time; rapid, completing the influenza subtyping within 6 hours; high specificity, ensured the specificity of the different subtypes by using two nested degenerate primers and one probe, no cross reaction occurring between the subtypes, no non-specific reactions with other pathogens and high sensitivity. When used separately to detect the product of single GM RT-PCR for single H5 or N1 gene, the GMPLex test showed a sensitivity of 10⁻⁵(= 280ELD₅₀) forboth tests and the Luminex qualitative ratio results were 3.08 and 3.12, respectively. When used to detect the product of GM RT-PCR for H5N1 strain at the same time, both showed a sensitivity of 10⁻⁴(=2800 ELD₅₀). The GMPLex rapid high throughput subtyping test can satisfy the needs of influenza rapid testing.

Influenza outbreaks during World Youth Day 2008 mass gathering

Influenza outbreaks during mass gatherings have been rarely described, and detailed virologic assessment is lacking. An influenza outbreak occurred during World Youth Day in Sydney, Australia, July 2008 (WYD2008). We assessed epidemiologic data and respiratory samples collected from attendees who sought treatment for influenza-like illness at emergency clinics in Sydney during this outbreak. Isolated influenza viruses were compared with seasonal influenza viruses from the 2008 influenza season. From 100 infected attendees, numerous strains were identified: oseltamivir-resistant influenza A (H1N1) viruses, oseltamivir-sensitive influenza A (H1N1) viruses, influenza A (H3N2) viruses, and strains from both influenza B lineages (B/Florida/4/2006-like and B/Malaysia/2506/2004-like). Novel viruses were introduced, and pre-WYD2008 seasonal viruses were amplified. Viruses isolated at mass gatherings can have substantial, complex, and unpredictable effects on community influenza activity. Greater flexibility by public health authorities and hospitals is required to appropriately manage and contain these outbreaks.

Rapid semi-automated quantitative multiplex tandem PCR (MT-PCR) assays for the differential diagnosis of influenza-like illness

BACKGROUND

Influenza A, including avian influenza, is a major public health threat in developed and developing countries. Rapid and accurate detection is a key component of strategies to contain spread of infection, and the efficient diagnosis of influenza-like-illness is essential to protect health infrastructure in the event of a major influenza outbreak.

METHODS

We developed a multiplexed PCR (MT-PCR) assay for the simultaneous diagnosis of respiratory viruses causing influenza-like illness, including the specific recognition of influenza A haemagglutinin subtypes H1, H3, and H5. We tested several hundred clinical specimens in two diagnostic reference laboratories and compared the results with standard techniques.

RESULTS

The sensitivity and specificity of these assays was higher than individual assays based on direct antigen detection and standard PCR against a range of control templates and in several hundred clinical specimens. The MT-PCR assays provided differential diagnoses as well as potentially useful quantitation of virus in clinical samples.

CONCLUSIONS

MT-PCR is a potentially powerful tool for the differential diagnosis of influenza-like illness in the clinical diagnostic laboratory.

Development of reverse transcription-loop-mediated isothermal amplification (RT-LAMP) assay for detection of avian influenza viruses in field specimens

Reverse transcription loop-mediated isothermal amplification (RT-LAMP) is an established gene amplification method for rapid diagnosis of various infectious diseases. In order to detect avian influenza viruses, particularly in field specimens, specific primers targeting the matrix gene were designed. Thirty-four virus samples, including isolates from wild and domestic avian hosts belonging to various geographical areas, were used to confirm the validity of the primers. All samples were confirmed to be positive in less than 1 hr. The RT-LAMP assay was also able to detect avian influenza virus in the various field samples, such as swabs, tissues, and feces. These results indicate that the developed RT-LAMP assay with uniquely designed primers is potentially useful in comprehensive avian influenza surveillance.

Surveillance for outbreaks of influenza-like illness in the institutionalized elderly

Respiratory outbreaks are common in aged-care facilities (ACFs), are both underreported and frequently identified late, and are often associated with considerable burden of illness and death. There is emerging evidence that active surveillance coupled with early and systematic intervention can reduce this burden. Active surveillance for influenza-like illness and rapid diagnosis of influenza were established in 16 ACFs in Sydney, Australia, prior to the winter of 2006. A point-of-care influenza test and laboratory direct immunofluorescence tests for common respiratory viruses were used for diagnosis. We achieved early identification of seven respiratory disease outbreaks, two of which were caused by influenza. For the influenza outbreaks, antiviral treatment and prophylaxis were initiated 4–6 days from symptom onset in the primary case. A simple active surveillance system for influenza was successfully implemented and resulted in early detection of influenza and other respiratory disease outbreaks. This enabled earlier implementation of prevention and control measures and increased the potential effectiveness of anti-influenza chemoprophylaxis.

Evaluation of twenty rapid antigen tests for the detection of human influenza A H5N1, H3N2, H1N1, and B viruses

Twenty rapid antigen assays were compared for their ability to detect influenza using dilutions of virus culture supernatants from human isolates of influenza A H5N1 (clade 1 and 2 strains), H3N2 and H1N1 viruses, and influenza B. There was variation amongst the rapid antigen assays in their ability to detect different influenza viruses. Six of the 12 assays labeled as distinguishing between influenza A and B had comparable analytical sensitivities for detecting both influenza A H5N1 strains, although their ability to detect influenza A H3N2 and H1N1 strains varied. The two assays claiming H5 specificity did not detect either influenza A H5N1 strains, and the two avian influenza-specific assays detected influenza A H5N1, but missed some influenza A H3N2 virus supernatants. Clinical trials of rapid antigen tests for influenza A H5N1 are limited. For use in a pandemic where novel influenza strains are circulating (such as the current novel influenza A H1N1 09 virus), rapid antigen tests should ideally have comparable sensitivity and specificity for the new strains as for co-circulating seasonal influenza strains.

Comparison of a rapid antigen test with nucleic acid testing during cocirculation of pandemic influenza A/H1N1 2009 and seasonal influenza A/H3N2

The rapid diagnosis of influenza is critical in optimizing clinical management. Rapid antigen tests have decreased sensitivity in detecting pandemic influenza A/H1N1 2009 virus compared to seasonal influenza A subtypes (53.4% versus 74.2%, P < 0.001). Nucleic acid tests should be used to detect pandemic influenza virus when rapid antigen tests are negative.

Influenza outbreak during Sydney World Youth Day 2008: the utility of laboratory testing and case definitions on mass gathering outbreak containment

BACKGROUND

Influenza causes annual epidemics and often results in extensive outbreaks in closed communities. To minimize transmission, a range of interventions have been suggested. For these to be effective, an accurate and timely diagnosis of influenza is required. This is confirmed by a positive laboratory test result in an individual whose symptoms are consistent with a predefined clinical case definition. However, the utility of these clinical case definitions and laboratory testing in mass gathering outbreaks remains unknown.

METHODS AND RESULTS

An influenza outbreak was identified during World Youth Day 2008 in Sydney. From the data collected on pilgrims presenting to a single clinic, a Markov model was developed and validated against the actual epidemic curve. Simulations were performed to examine the utility of different clinical case definitions and laboratory testing strategies for containment of influenza outbreaks. Clinical case definitions were found to have the greatest impact on averting further cases with no added benefit when combined with any laboratory test. Although nucleic acid testing (NAT) demonstrated higher utility than indirect immunofluorescence antigen or on-site point-of-care testing, this effect was lost when laboratory NAT turnaround times was included. The main benefit of laboratory confirmation was limited to identification of true influenza cases amenable to interventions such as antiviral therapy.

CONCLUSIONS

Continuous re-evaluation of case definitions and laboratory testing strategies are essential for effective management of influenza outbreaks during mass gatherings.

The use of oseltamivir during an influenza B outbreak in a chronic care hospital

BACKGROUND

Residents of nursing homes and long-term care facilities are at a higher risk of outbreaks of influenza and of serious complications of influenza than those in the community. In late July 2005, a 90-bed chronic care psycho-geriatric hospital in Sydney, Australia, reported cases of influenza-like illness (ILI) occurring amongst its residents.

METHODS

An investigation to confirm the outbreak, and its cause, was undertaken. Influenza vaccination levels amongst residents, and the effects of antiviral drugs used for prevention and treatment, were assessed. Oseltamivir was only given to the residents, in the form of both treatment and prophylaxis.

RESULTS

A total of 22 out of 89 residents met the clinical case definition of ILI with onset on or after 27 July 2005. This represents an attack rate of 25%. Oseltamivir was commenced on day 9 of the outbreak. Influenza B was identified in six residents as the causative agent of the outbreak. No deaths or acute hospitalization were recorded for this outbreak and there were no further reported cases after the introduction of oseltamivir. Vaccine effectiveness was 75% and the strain of influenza B isolated was well matched to that year's vaccine.

CONCLUSIONS

There are few data on the use of oseltamivir in influenza B outbreaks. Early antiviral intervention appeared to curtail this outbreak of influenza B in a chronic care facility. We found high vaccine effectiveness in this frail, institutionalized population, highlighting the importance of influenza vaccination for residents of chronic care facilities.

Rapid subtyping of H9N2 influenza virus by a triple reverse transcription polymerase chain reaction

The aim of this study was to develop a rapid, cost-saving triple reverse transcription polymerase chain reaction (triple RT-PCR) for subtyping H9N2 avian influenza viruses (AIVs). The three primer pairs for amplification of target sequences of nucleoprotein (NP), hemagglutinin (HA) and neuraminidase (NA) genes, respectively, were designed for subtyping the viruses in the triple RT-PCR. The sensitivity of triple RT-PCR was found to be 10(2) copies per reaction for each of NP, H9 and N2 gene. The specificity tests indicated that all of NP, HA and NA genes were positive for H9N2, only NP gene was positive for H5N1 and H1N1 AIVs, and the results were negative for the other avian viruses including Newcastle disease virus, infectious bronchitis virus, infectious bursal disease virus, duck hepatitis virus and avian encephalomyelitis virus. A total of 112 clinical samples were evaluated by the assay and the results showed that the sensitivity and specificity of triple RT-PCR were in accordance with the virus isolation. In conclusion, this method is rapid and cost-effective making it feasible and attractive for large-scale epidemiological investigation of H9N2 influenza virus.

Guillain-Barré syndrome and influenza virus infection

BACKGROUND

In Western countries, the cause of 60% of all Guillain-Barré syndrome (GBS) cases remains unidentified. The number of cases of unidentified cause peaks in winter, and these cases are commonly preceded by respiratory tract infection or influenza-like illness. We investigated the triggering role of influenza virus infection.

METHODS

Of 405 patients with GBS who were admitted to a French reference center during 1996-2004, 234 had cases caused by an unidentified agent. We used time-series methods to study the correlation between the monthly incidence of such cases and influenza-like illnesses reported by the Sentinelles surveillance network. We analyzed anti-influenza antibodies using complement fixation testing and hemagglutination-inhibition assays. We studied etiological subgroups using Wilcoxon and Fisher's exact tests.

RESULTS

We found a positive association between the monthly incidence of GBS caused by an unidentified agent and reported influenza-like illnesses. Of 73 patients whose cases occurred during periods in which there was a possible link to influenza, 10 (13.7%) had serological evidence of recent influenza A, and 4 (5.5%) had serological evidence of influenza B. Eight of 10 influenza A-related cases occurred during "major" influenza seasons, and antibodies specific to the current epidemic strain were found in 9 cases. Most patients with influenza A-related cases were aged < 65 years, and none had antiganglioside antibodies. Influenza-related cases differed both from Campylobacter jejuni-related cases, with regard to the lack of need for mechanical ventilation (P = .014), and from the cases caused by an unidentified agent, with regard to the presence of preceding influenza-like illness or respiratory tract infection (P = .015) and longer time from the infectious event to GBS onset (P = .04).

CONCLUSIONS

Influenza viruses are infrequent triggering agents of GBS but may play a significant role during major influenza outbreaks. Influenza-related GBS displays specific features and is not associated with antiganglioside antibody response, which suggests the presence of underlying immune mechanisms.

Early diagnosis of lower respiratory tract infections (point-of-care tests)

PURPOSE OF REVIEW

Respiratory tract infections are a common reason for prescribing antibiotics, although not all of these infections require such therapy. Rapid diagnosis of etiology using point-of-care tests is a potentially useful way of reducing prescriptions of both unnecessary and unnecessarily broad-spectrum antibiotics. This can also lead to the facilitation of appropriate infection control measures to prevent spread of respiratory viruses within institutions.

RECENT FINDINGS

Point-of-care tests are available for diagnosing influenza, respiratory syncytial virus, Streptococcus pneumoniae, and Legionella infections using easily obtainable specimens. Their main benefit is that results can be obtained in about 15 min with reasonable accuracy. In many situations, however, it is still important to confirm diagnosis with more accurate but slower tests such as bacterial cultures with antibacterial susceptibility testing or viral polymerase chain reaction testing.

SUMMARY

Although the sensitivities of many of the rapid diagnostic tests are moderate, when used at the time of initial consultation, they have the potential to reduce costs, length of stay, secondary spread of respiratory viruses, and inappropriate antibiotic prescribing.

Development of reverse transcription loop-mediated isothermal amplification for rapid detection of H9 avian influenza virus

Reverse transcription loop-mediated isothermal amplification (RT-LAMP) is a unique gene amplification method that can be completed within 45 min at 63 degrees C. In this study, RT-LAMP was used to develop a rapid and sensitive laboratory diagnostic system for the H9 subtype of avian influenza virus (AIV). The experiment results from the reference strains demonstrated that the established RT-LAMP sensitivity was 10-fold higher than that of RT-PCR, with the detection limit of 10 copies per reaction, and no cross-reactivity was observed from the samples of other related viruses including H5N1, H3N2 subtype of AIV and Newcastle disease virus. Furthermore, a total of 112 clinical samples were tested by RT-LAMP, RT-PCR, and virus isolation, respectively. All of the 85 positive specimens identified by virus isolation were also positive by RT-LAMP, while 7 of these samples were missed by RT-PCR. These results suggest that the present RT-LAMP system may provide a new avenue for the recognition of H9 subtype virus, and may be employed to screen for potential carriers in wild and domestic birds.

Influenza infection and risk of acute pulmonary embolism

BACKGROUND

Influenza infections have been associated with procoagulant changes. Whether influenza infections lead to an increased risk of pulmonary embolism remains to be established.

METHODS

We conducted a nested case control study in a large cohort of patients with a clinical suspicion of having pulmonary embolism. Blood samples were collected to investigate the presence of influenza A and B by complement fixation assay (CFA). We compared case patients, in whom pulmonary embolism was proven (n = 102), to controls, in whom pulmonary embolism was excluded (n = 395). Furthermore, we compared symptoms of influenza-like illness in both patient groups 2 weeks prior to inclusion in the study, using the influenza-like illness (ILI) score, which is based on a questionnaire. We calculated the risk of pulmonary embolism associated with influenza infection.

RESULTS

The percentage of patients with influenza A was higher in the control group compared to the case group (4.3% versus 1.0%, respectively, odds ratio 0.22; 95% CI: 0.03-1.72). Influenza B was not detectable in any of the cases and was found in 3 of the 395 controls (0.8%). The ILI score was positive in 24% of the cases and 25% in the control persons (odds ratio 1.16, 95% CI: 0.67-2.01). We did not observe an association between the ILI score and proven influenza infection.

CONCLUSION

In this clinical study, influenza infection was not associated with an increased risk of acute pulmonary embolism. The ILI score is non-specific in this clinical setting.

Point‐of‐care testing for community‐acquired pneumonia: do we have all the answers?

Point-of-care tests (POCTs) are available for rapid, "bedside" diagnosis of some causes of community-acquired pneumonia. POCTs complement other laboratory investigations for pneumonia. Although their sensitivity and specificity are improving, they are generally less sensitive than nucleic acid amplification and culture techniques. Questions remain as to the most cost-effective use of POCTs in clinical practice. To ensure their maximum value for both individual patients and the public health system, POCTs are probably best used as part of laboratory-designed algorithms for investigating pneumonia. POCTs are a valuable tool for surveillance, for rapid investigation of outbreaks, and for use in laboratories with limited diagnostic facilities.

Laboratory diagnosis of human seasonal and pandemic influenza virus infection

Laboratory diagnosis is important to distinguish influenza from other respiratory virus infections. It will be especially important in detecting the first cases of pandemic influenza.

Good quality respiratory tract sampling is needed to maximise diagnostic yield in influenza infection.

In the appropriate clinical setting, pandemic strain‐specific nucleic acid testing is the initial test of choice for suspected pandemic influenza. It is more sensitive than virus isolation, and more sensitive and specific than serology, immunofluorescence and other antigen detection methods.

Virus isolation is needed to monitor new influenza strains and for vaccine development. Analysis of influenza isolates is undertaken by the World Health Organization Global Influenza Surveillance Network.

Monitoring for antiviral resistance will be needed with widespread use of neuraminidase inhibitors for treatment and prophylaxis during a pandemic.

Review of Human Infections with Avian Influenza H5N1 and Proposed Local Clinical Management Guideline

Introduction: The current avian and human H5N1 influenza epidemic has been in resurgence since 2004. We decided to evaluate published evidence in relation to epidemiology, clinical features and course, laboratory diagnosis, treatment and outcome of human H5N1 influenza, and develop institutional clinical management guidelines. Methods: A search of PubMed was conducted for all English language articles with search terms “avian”, “influenza” and “H5N1”. The bibliography of articles was searched for other references of interest. Results: Published case series from Hong Kong in 1997, and Thailand and Vietnam since 2004 have indicated a rapidly progressive primary viral pneumonia resulting in acute respiratory distress syndrome. The majority of human H5N1 infections can be linked to poultry exposure. Hitherto there has been no evidence of efficient human-to-human transmission. Case fatality rates have varied from 71% in Thailand to 100% in Cambodia. Oseltamivir appears to be the only potentially effective antiviral therapy. H5N1 isolates in Vietnam have become resistant to oseltamivir, resulting in persistent viral replication and death. There is as yet no effective human H5N1 vaccine. Conclusions: National and international preparedness plans are well advised. Clinical trials to evaluate higher dose oseltamivir therapy and immunomodulatory treatment are urgently needed. Key words: H5N1 subtype, Influenza A, Influenza in birds, Literature review

Detection of human influenza A viruses by loop-mediated isothermal amplification

Here we describe the use of the loop-mediated isothermal amplification (LAMP) method to detect human influenza viruses (H1 to H3). Our results were correlated 100% with results deduced from routine clinical diagnostic tests. In addition, we also developed a LAMP assay specific for human beta-actin cDNA as a quality control test.

Microsphere-based duplexed immunoassay for influenza virus typing by flow cytometry

We have developed a rapid, duplexed microsphere-based immunoassay for the characterization of influenza virus types that has the potential to overcome many of the limitations of current detection methods. The assay uses microspheres of two sizes, each coupled to an influenza type A- or type B-specific monoclonal antibody (MAb), to capture influenza viruses in the sample. A cocktail of fluorescently labeled, influenza-specific polyclonal antibodies then binds the captured viruses. The sandwich complexes are measured using a multiparameter flow cytometer. The assay can distinguish between influenza types A and B in a single reaction with good reproducibility and high sensitivity. Detection sensitivity is much higher than that of commercially available influenza diagnosis quick kits: the FLU OIA (Thermo Biostar) kit and the Directigen Flu A+B kit (Becton Dickinson). The multiplexing capabilities of the current assay, which are not possible with enzyme-linked immunosorbent assay (ELISA) and the commercially available kits, reduce sample handling and consume fewer costly reagents. This assay represents a more efficient and sensitive method of characterizing influenza types. With inclusion of influenza subtype-specific antibodies as capture antibodies, this microsphere-based immunoassay can be expanded to differentiate among influenza types and subtypes in a single reaction to improve world-wide influenza surveillance.