tetano
Editor, Senior Moderator
Front Public Health. 2015 Nov 10;3:250.
[h=1]Seasonal Influenza Epidemics and El Ni?os.[/h] Oluwole OS[SUP]1[/SUP].
[h=3]Author information[/h]
[h=3]Abstract[/h] Seasonal influenza epidemics occur annually during the winter in the northern and southern hemispheres, but timing of peaks and severity vary seasonally. Low humidity, which enhances survival and transmission of influenza virus, is the major risk factor. Both El Ni?o and La Ni?a phases of El Ni?o-southern oscillation (ENSO), which determine inter-annual variation of precipitation, are putative risk factors. This study was done to determine if seasonality, timing of peak, and severity of influenza epidemics are coupled to phases of ENSO. Monthly time series of positive specimens for influenza viruses and of multivariate El Ni?o-Southern Oscillation Index from January 2000 to August 2015 were analyzed. Seasonality, wavelet spectra, and cross-wavelet spectra analyses were performed. Of 31 countries in the dataset, 21 were in the northern hemisphere and 10 in the southern hemisphere. The highest number of influenza cases occurred in January in the northern hemisphere, but in July in the southern hemisphere, p < 0.0001. Seasonal influenza epidemic was coupled to El Ni?o, while low occurrence was coupled to La Ni?a. The moderate La Ni?a of 2010-2011 was followed by weak seasonal influenza epidemic. The influenza pandemic of 2009-2010 followed the moderate El Ni?o of 2009-2010, which had three peaks. Spectrograms showed time-varying periodicities of 6-48 months for ENSO, 6-24 months for influenza in the northern hemisphere, and 6-12 months for influenza in the southern hemisphere. Cross spectrograms showed time-varying periodicities at 6-36 months for ENSO and influenza in both hemispheres, p < 0.0001. Phase plots showed that influenza time series lagged ENSO in both hemispheres. Severity of seasonal influenza increases during El Ni?o, but decreases during La Ni?a. Coupling of seasonality, timing, and severity of influenza epidemics to the strength and waveform of ENSO indicate that forecast models of El Ni?o should be integrated into surveillance programs for influenza epidemics.
[h=4]KEYWORDS:[/h] El Ni?o; La Ni?a; climate; epidemic; flu; influenza; pandemic; seasonal
PMID: 26618150 [PubMed - as supplied by publisher]
[h=1]Seasonal Influenza Epidemics and El Ni?os.[/h] Oluwole OS[SUP]1[/SUP].
[h=3]Author information[/h]
[h=3]Abstract[/h] Seasonal influenza epidemics occur annually during the winter in the northern and southern hemispheres, but timing of peaks and severity vary seasonally. Low humidity, which enhances survival and transmission of influenza virus, is the major risk factor. Both El Ni?o and La Ni?a phases of El Ni?o-southern oscillation (ENSO), which determine inter-annual variation of precipitation, are putative risk factors. This study was done to determine if seasonality, timing of peak, and severity of influenza epidemics are coupled to phases of ENSO. Monthly time series of positive specimens for influenza viruses and of multivariate El Ni?o-Southern Oscillation Index from January 2000 to August 2015 were analyzed. Seasonality, wavelet spectra, and cross-wavelet spectra analyses were performed. Of 31 countries in the dataset, 21 were in the northern hemisphere and 10 in the southern hemisphere. The highest number of influenza cases occurred in January in the northern hemisphere, but in July in the southern hemisphere, p < 0.0001. Seasonal influenza epidemic was coupled to El Ni?o, while low occurrence was coupled to La Ni?a. The moderate La Ni?a of 2010-2011 was followed by weak seasonal influenza epidemic. The influenza pandemic of 2009-2010 followed the moderate El Ni?o of 2009-2010, which had three peaks. Spectrograms showed time-varying periodicities of 6-48 months for ENSO, 6-24 months for influenza in the northern hemisphere, and 6-12 months for influenza in the southern hemisphere. Cross spectrograms showed time-varying periodicities at 6-36 months for ENSO and influenza in both hemispheres, p < 0.0001. Phase plots showed that influenza time series lagged ENSO in both hemispheres. Severity of seasonal influenza increases during El Ni?o, but decreases during La Ni?a. Coupling of seasonality, timing, and severity of influenza epidemics to the strength and waveform of ENSO indicate that forecast models of El Ni?o should be integrated into surveillance programs for influenza epidemics.
[h=4]KEYWORDS:[/h] El Ni?o; La Ni?a; climate; epidemic; flu; influenza; pandemic; seasonal
PMID: 26618150 [PubMed - as supplied by publisher]