tetano
Editor, Senior Moderator
Clin Microbiol Infect. 2019 Nov 21. pii: S1198-743X(19)30617-2. doi: 10.1016/j.cmi.2019.11.018. [Epub ahead of print] [h=1]Association between type-specific influenza circulation and incidence of severe laboratory-confirmed cases; which subtype is the most virulent?[/h]
Lytras T[SUP]1[/SUP], Andreopoulou A[SUP]2[/SUP], Gkolfinopoulou K[SUP]2[/SUP], Mouratidou E[SUP]2[/SUP], Tsiodras S[SUP]3[/SUP].
[h=3]Author information[/h] 1 National Public Health Organization, Athens, Greece. Electronic address: thlytras@gmail.com. 2 National Public Health Organization, Athens, Greece. 3 National Public Health Organization, Athens, Greece; 4th Department of Internal Medicine, Attikon University Hospital, University of Athens Medical School, Athens, Greece.
[h=3]Abstract[/h] [h=4]OBJECTIVES:[/h] Excess population mortality during winter is most often associated with influenza A(H3N2), though susceptibility differs by age. We examined differences between influenza types/subtypes in their association with severe laboratory-confirmed cases, overall and by age group, to determine which type is the most virulent.
[h=4]METHODS:[/h] We used nine seasons of comprehensive nationwide surveillance data from Greece (2010-2011 to 2018-2019) to examine the association, separately for influenza A(H1N1)pdm09, A(H3N2) and B, between the number of laboratory-confirmed severe cases (intensive care hospitalizations or deaths) per type/subtype and the overall type-specific circulation during the season (expressed as a cumulative incidence proxy). Quasi-Poisson models with identity link were used, and multiple imputation to handle missing influenza A subtype.
[h=4]RESULTS:[/h] For the same level of viral circulation and across all ages, influenza A(H1N1)pdm09 was associated with twice as many intensive care hospitalizations as A(H3N2) (Rate Ratio [RR] 1.89, 95%CI 1.38-2.74) and three times more than influenza B (RR 3.27, 95%CI 2.54-4.20). Similar associations were observed for laboratory-confirmed deaths. A(H1N1)pdm09 affected adults over 40 years at similar rates, whereas A(H3N2) affected the elderly at a much higher rate than younger persons (>=65 vs 40-64 years, RR for intensive care 5.42, 95%CI 3.45-8.65, and RR for death 6.19, 95%CI 4.05-9.38). Within the 40-64 years age group, A(H1N1)pdm09 was associated with an approximately five times higher rate of severe disease compared to both A(H3N2) and B.
[h=4]CONCLUSIONS:[/h] Influenza A(H1N1)pdm09 is associated with many more severe laboratory-confirmed cases, likely due to a more typical clinical presentation and younger patient age, leading to more testing. A(H3N2) affects older people more, with cases less often recognized and confirmed.
Copyright ? 2019 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.
[h=4]KEYWORDS:[/h] infectious disease surveillance; influenza; influenza complications; influenza types/subtypes; intensive careunits; mortality; virulence
PMID: 31760112 DOI: 10.1016/j.cmi.2019.11.018
Lytras T[SUP]1[/SUP], Andreopoulou A[SUP]2[/SUP], Gkolfinopoulou K[SUP]2[/SUP], Mouratidou E[SUP]2[/SUP], Tsiodras S[SUP]3[/SUP].
[h=3]Author information[/h] 1 National Public Health Organization, Athens, Greece. Electronic address: thlytras@gmail.com. 2 National Public Health Organization, Athens, Greece. 3 National Public Health Organization, Athens, Greece; 4th Department of Internal Medicine, Attikon University Hospital, University of Athens Medical School, Athens, Greece.
[h=3]Abstract[/h] [h=4]OBJECTIVES:[/h] Excess population mortality during winter is most often associated with influenza A(H3N2), though susceptibility differs by age. We examined differences between influenza types/subtypes in their association with severe laboratory-confirmed cases, overall and by age group, to determine which type is the most virulent.
[h=4]METHODS:[/h] We used nine seasons of comprehensive nationwide surveillance data from Greece (2010-2011 to 2018-2019) to examine the association, separately for influenza A(H1N1)pdm09, A(H3N2) and B, between the number of laboratory-confirmed severe cases (intensive care hospitalizations or deaths) per type/subtype and the overall type-specific circulation during the season (expressed as a cumulative incidence proxy). Quasi-Poisson models with identity link were used, and multiple imputation to handle missing influenza A subtype.
[h=4]RESULTS:[/h] For the same level of viral circulation and across all ages, influenza A(H1N1)pdm09 was associated with twice as many intensive care hospitalizations as A(H3N2) (Rate Ratio [RR] 1.89, 95%CI 1.38-2.74) and three times more than influenza B (RR 3.27, 95%CI 2.54-4.20). Similar associations were observed for laboratory-confirmed deaths. A(H1N1)pdm09 affected adults over 40 years at similar rates, whereas A(H3N2) affected the elderly at a much higher rate than younger persons (>=65 vs 40-64 years, RR for intensive care 5.42, 95%CI 3.45-8.65, and RR for death 6.19, 95%CI 4.05-9.38). Within the 40-64 years age group, A(H1N1)pdm09 was associated with an approximately five times higher rate of severe disease compared to both A(H3N2) and B.
[h=4]CONCLUSIONS:[/h] Influenza A(H1N1)pdm09 is associated with many more severe laboratory-confirmed cases, likely due to a more typical clinical presentation and younger patient age, leading to more testing. A(H3N2) affects older people more, with cases less often recognized and confirmed.
Copyright ? 2019 European Society of Clinical Microbiology and Infectious Diseases. Published by Elsevier Ltd. All rights reserved.
[h=4]KEYWORDS:[/h] infectious disease surveillance; influenza; influenza complications; influenza types/subtypes; intensive careunits; mortality; virulence
PMID: 31760112 DOI: 10.1016/j.cmi.2019.11.018