A Summer Outbreak of Influenza A Virus Infection among Young Children

Evidence for an increase in the intensity of inter-seasonal influenza, Queensland, Australia, 2009-2019

BACKGROUND

Inter-seasonal influenza cases have been increasing in Australia. Studies of influenza seasonality typically focus on seasonal transmission in temperate regions, leaving our understanding of inter-seasonal epidemiology limited. We aimed to improve understanding of influenza epidemiology during inter-seasonal periods across climate zones, and explored influenza intensity and strain dominance patterns over time.

METHODS

Queensland state-wide laboratory-confirmed influenza notifications and public laboratory influenza test data from 2009-2019 were described by demographics, time period, region and strain type. We compared influenza intensity over time using the WHO Average Curve method to provide thresholds for seasonal and inter-seasonal periods.

RESULTS

Among the 243 830 influenza notifications and 490 772 laboratory tests reported in Queensland between 2009 and 2019, 15% of notifications and 40% of tests occurred during inter-seasonal periods, with 6.3% of inter-seasonal tests positive. Inter-seasonal notifications and tests substantially increased over time and increases in weekly proportions positive and intensity classifications suggested gradual increases in virus activity. Tropical inter-seasonal activity was higher with periods of marked increase. Influenza A was dominant, although influenza B represented up to 72% and 42% of notifications during some seasonal and inter-seasonal periods, respectively.

CONCLUSIONS

Using notification and testing data, we have demonstrated a gradual increase in inter-seasonal influenza over time. Our findings suggest this increase results from an interplay between testing, activity and intensity, and strain circulation. Seasonal intensity and strain circulation appeared to modify subsequent period intensity. Routine year-round surveillance data would provide a better understanding of influenza epidemiology during this infrequently studied inter-seasonal time period.

An Epidemiological Analysis of Summer Influenza Epidemics in Okinawa

Objective This study evaluates the difference between winter influenza and summer influenza in Okinawa. Methods From January 2007 to June 2014, weekly rapid antigen test (RAT) results performed in four acute care hospitals were collected for the surveillance of regional influenza prevalence in the Naha region of the Okinawa Islands. Results An antigenic data analysis revealed that multiple H1N1 and H3N2 viruses consistently co-circulate in Okinawa, creating synchronized seasonal patterns and a high genetic diversity of influenza A. Additionally, influenza B viruses play a significant role in summer epidemics, almost every year. To further understand influenza epidemics during the summer in Okinawa, we evaluated the full genome sequences of some representative human influenza A and influenza B viruses isolated in Okinawa. Phylogenetic data analysis also revealed that multiple H1N1 and H3N2 viruses consistently co-circulate in Okinawa. Conclusion This surveillance revealed a distinct epidemic pattern of seasonal and pandemic influenza in this subtropical region.

Summer influenza outbreak in a home for the elderly: application of preventive measures

Influenza outbreaks occasionally occur in nursing homes (NHs) despite vaccination, but occurrence during summer is a rare event. We describe an influenza outbreak during a heatwave in 2005, and discuss the usefulness of rapid diagnosis in facilitating early intervention as well as appropriate infection control measures. An outbreak was observed in a single NH with 81 residents (mean age 88 years) and 48 healthcare workers (HCWs) and lasted seven days. Fever, cough and wheezing were reported as the main symptoms in 32 affected residents (39.5%) and 6 (12.5%) HCWs. Influenza was suspected and provisionally confirmed by a rapid diagnostic test performed on specimens from four patients. The outbreak was further confirmed by culture and reverse transcriptase-polymerase chain reaction in seven out of 10 residents. The strain was similar to the winter epidemic strain of the 2004-2005 season: H3N2A/New York/55/2004. As soon as the outbreak was confirmed, a crisis management team was set up with representatives of the local health authority and NH staff. A package of measures was implemented to control the outbreak, including patient isolation and the wearing of surgical masks by all residents and staff. A therapeutic course of oseltamivir was prescibed to 19/32 symptomatic patients and to 5/6 HCWs, and 47 residents and 42 remaining HCWs received a prophylactic post-exposure regimen. The outbreak ended within 48 h. Case fatality rate was 15.6% among residents. Pre-outbreak influenza vaccine coverage among the residents was 93.5% and 41.7% in HCWs. The rapid diagnostic test enabled prompt action to be taken, which facilitated infection control measures.

Emergence of oseltamivir-resistant influenza A/H3N2 virus with altered hemagglutination pattern in a hematopoietic stem cell transplant recipient

BACKGROUND

Persistent influenza virus replication during antiviral therapy in patients undergoing hematopoietic stem cell transplantation (HSCT) could promote the emergence of antiviral drug resistance.

OBJECTIVES

To follow the viral genotypic and drug susceptibility changes in a patient who developed progressive influenza A/H3N2 pneumonia despite oseltamivir therapy after haploidentical HSCT.

STUDY DESIGN

Direct genotypic analysis of the neuraminidase (NA) and hemagglutinin (HA) genes in successive bronchoalveolar lavage specimens was employed in combination with hemagglutination and NA enzymatic activity assays of the corresponding viral isolates.

RESULTS

The emergence of NA oseltamivir-resistance mutation R292K was detected by 12 days of oseltamivir treatment with 44,286-fold increase in oseltamivir IC50. Resurgence of wild type viral population was identified by 7 days after cessation of oseltamivir. Sequential HA mutations R228S and A138S were identified and associated with a shift in the HA receptor binding pattern reflected by loss of the ability to agglutinate chicken erythrocytes.

CONCLUSIONS

These rapid evolutionary changes warrant close virologic monitoring of immunocompromised patients treated for influenza infection, and raise concern about the efficacy of mono-drug therapy for influenza-associated disease in HSCT recipients.

Potential for early warning of viral influenza activity in the community by monitoring clinical diagnoses of influenza in hospital emergency departments

BACKGROUND

Although syndromic surveillance systems are gaining acceptance as useful tools in public health, doubts remain about whether the anticipated early warning benefits exist. Many assessments of this question do not adequately account for the confounding effects of autocorrelation and trend when comparing surveillance time series and few compare the syndromic data stream against a continuous laboratory-based standard. We used time series methods to assess whether monitoring of daily counts of Emergency Department (ED) visits assigned a clinical diagnosis of influenza could offer earlier warning of increased incidence of viral influenza in the population compared with surveillance of daily counts of positive influenza test results from laboratories.

METHODS

For the five-year period 2001 to 2005, time series were assembled of ED visits assigned a provisional ED diagnosis of influenza and of laboratory-confirmed influenza cases in New South Wales (NSW), Australia. Poisson regression models were fitted to both time series to minimise the confounding effects of trend and autocorrelation and to control for other calendar influences. To assess the relative timeliness of the two series, cross-correlation analysis was performed on the model residuals. Modelling and cross-correlation analysis were repeated for each individual year.

RESULTS

Using the full five-year time series, short-term changes in the ED time series were estimated to precede changes in the laboratory series by three days. For individual years, the estimate was between three and 18 days. The time advantage estimated for the individual years 2003-2005 was consistently between three and four days.

CONCLUSION

Monitoring time series of ED visits clinically diagnosed with influenza could potentially provide three days early warning compared with surveillance of laboratory-confirmed influenza. When current laboratory processing and reporting delays are taken into account this time advantage is even greater.

Influenza A/Fujian/411/02(H3N2)-lineage viruses in Finland: genetic diversity, epidemic activity and vaccination-induced antibody response

The first sporadic cases of Fujian/411/02-lineage viruses were recorded in Finland in winter 2001-2002. The first protracted but low-intensity outbreak occurred here during the first half of 2003, and the second outbreak early in autumn 2003, after detection of sporadic influenza A cases in the summer. The calculated incidence of influenza A in the Finnish army was 515/10000 during the first outbreak and 2066/10000 during the second outbreak. During the 2003-2004 epidemic season, the isolates fell into three groups for their haemagglutinin (HA1) sequences. In groups I and II, the strains were reassortants which differed for their neuraminidase (NA) sequences from the viruses of the previous spring. Group II viruses, which predominated in Finland during the 2003-2004 season, were characterized by loss of the glycosylation site at position 126 in HA1. The relevance of this loss to the epidemiology is discussed, as well as the frequent appearance of codominant amino acid mixtures at position 151 lining the catalytic cavity of the NA. Group III viruses, genetically related to Wellington/1/2004, the drift variant predominant in 2004 in the southern hemisphere, caused some localized outbreaks in Finland towards the end of the 2003-2004 epidemic. The antigenic match between the vaccine virus (Panama/2007/99) and the Fujian-lineage epidemic viruses in winter 2003-2004 was far from optimal. Nevertheless, high levels of prevaccination and postvaccination antibodies to the predomi- nant group II virus were recorded. Lower antibody levels were detected to the group III virus, which turned out to be a herald strain that reappeared in Finland during the following epidemic season.