Hypothesis on a possible role of El Niño in the occurrence of influenza pandemics

Abstract

The El Niño phenomenon is the Earth’s strongest climatic fluctuation on an inter-annual time-scale and has a quasi-global impact although originating in the tropical Pacific Ocean. A very strong El Niño is recognized to cause extreme dryness and wetness in different parts of the world. We show that all the eight well documented influenza pandemics, starting from the first certain one documented in AD 1580, originated in China and in Russia, a few years after the occurrence of a very strong or after a prolonged strong/moderate El Niño event. At present, the next El Niño will probably occur at the beginning of 2013 (Mazzarella et al., 2010) and this forecast may suggest to be well prepared to take appropriate precautionary epidemiological measures

The El Niño–Southern Oscillation (ENSO)–pandemic Influenza connection: Coincident or causal?

“…A recent paper by Mazzarella et al (27), published while this paper was in initial review, has posited that influenza pandemics have been preceded by moderate to strong El Niño events rather than La Niña events. We disagree with these findings and conclusions.…”

“…We disagree with these findings and conclusions. The work by Mazzarella et al (27) includes five pandemic events that occurred before the 20th century, for which onset dating is uncertain, but excludes the best-documented and most recent 2009 pandemic from the analysis. Inclusion of all well-dated pandemics and only well-dated pandemics is needed so that conditions during the appropriate time period-before the emergence of the virus in humans-are used in analysis.…”

“…Ultimately, omissions, errors in attribution, and errors in the ENSO reconstruction used (28) invalidate the findings and conclusions in the work by Mazzarella et al (27). Specifically, the 2009 pandemic is omitted, the 1957 and 1968 pandemics do not follow El Niño events, which Mazzarella et al (27) mistakenly claim, and conditions preceding the 1918 pandemic are incorrectly labeled El Niño in the dataset by Quinn et al (28) used in the work by Mazzarella et al (27).…”

“…Specifically, the 2009 pandemic is omitted, the 1957 and 1968 pandemics do not follow El Niño events, which Mazzarella et al (27) mistakenly claim, and conditions preceding the 1918 pandemic are incorrectly labeled El Niño in the dataset by Quinn et al (28) used in the work by Mazzarella et al (27). Furthermore, the work by Mazzarella et al (27) uses data from before 1850 for which the dating of both pandemic emergence and ENSO are less precise. As a result of these problems in their analysis, the work by Mazzarella et al (27) misses the association between La Niña phase events and subsequent pandemic emergence.…”

“…Furthermore, the work by Mazzarella et al (27) uses data from before 1850 for which the dating of both pandemic emergence and ENSO are less precise. As a result of these problems in their analysis, the work by Mazzarella et al (27) misses the association between La Niña phase events and subsequent pandemic emergence.…”