This project is to characterize the climatic variables associated with the spring influenza introduction in Minnesota turkeys.

1. The influence of climate on influenza A virus
(IAV) introductions in Minnesota turkeys:
Spring 2007 - 2015
Xi Guo
1
, Nitipong Homwong
2
, Jeanette Munoz-Aguayo
3
, Cristian Flores
3
,
Carol J. Cardona
1

2. Introduction
• Climate affects the transmission cycle of infectious diseases
• The landscape that gives rise to the transmission of influenza A virus
(IAV) between wild and domesticated avian species is greatly impacted by
the climate.
• The behavior of the wild waterfowl, the natural host of IAV, is also
affected by the climate condition.
• In the spring of 2015, highly pathogenic avian influenza (HPAI)
H5N2 was introduced to turkeys in Minnesota (MN). Prior to
2015, there were seven low pathogenic avian influenza (LPAI)
introductions occurred in the same area and the same season in
the turkey flocks.

3. List of Spring introductions of IAV
*The dates were based on an estimation of the date of
infection from positive serological and virological findings
Case ID Year Date Subtype County
1 2007 03/22* H7N9 Brown
2 2009 05/06* H7N9 Redwood
3 2011 05/13* H7N9 Wright
4 2012 04/26* H8N4 Kandiyohi
5 2013 05/08* H3N2/H9N2 Kandiyohi
6 2014 05/09 H4N2 Kandiyohi
7 2015 02/27 H5N2 Pope
8 2015 03/22 H5N2 Lac Qui Parle
9 2015 04/08 H5N2 Kandiyohi
10 2016 03/14 H1N1 Kandiyohi

4. Objective
To characterize the climate conditions associated with the Spring
introductions of IAV in MN turkeys.

5. Data source
Daily climatic variables including maximum temperature,
minimum temperature and snow depths during 1960-2015
were retrieved from the National Climatic Data Center
(NCDC) archives.The weather stations selected for data
analysis were within 20 miles of the case sites, which were
clustered into five regions.

6. Weather data analysis
• Spearman correlation was performed between the week of the
introduction cases and the weather indicators including
temperature 7 to 9°C, heading degree days (HDD) 18 to 20
days, and the yearly average temperature.
• Wilcoxon Ranked-sum tests were performed to compare the
sum of introduction years and non-introduction years.
• Permutation tests were performed to validate the significance
between the mean difference of temperature and snow depth
between introduction years and non-introduction years.

7. Result - Temporal pattern of temperature

8. Result - Temporal pattern of temperature
• The relationship between Case 7 and the lowest point resembles the
temporal pattern illustrated by Liu et al (Plos one, 2007), recapitulating
the same climate condition for HPAI introductions.
• The temperature pattern of other LPAI cases is different from Case 7,
suggesting different mechanism of HPAI and LPAI introductions.

9. Result - Weather indicator correlation
Weather indicator
Spearman
correlation p value
Spearman
correlation
coefficient
The
week
when
weekly
average
temperature
was
the
closest
to
7
°C
0.2005 0.5062
The
week
when
weekly
average
temperature
was
the
closest
to
8
°C
0.0083* 0.8447
The
week
when
weekly
average
temperature
was
the
closest
to
9
°C
0.0532 0.7000
The week when weekly average
temperature was the closest to the
yearly average
0.1344 0.5768
The week in which weekly average HDD
was the closest to 18
0.0083* 0.8447
The week in which weekly average HDD
was the closest to 19
0.0137* 0.8149
The week in which weekly average HDD
was the closest to 20
0.2005 0.5062

10. Result - Weather indicator correlation
• The relationship between Case 7 and the lowest point resembles the
temporal pattern illustrated by Liu et al (Plos one, 2007), recapitulating
the same climate condition for HPAI introductions.
• The temperature pattern of other LPAI cases is different from Case 7,
suggesting different mechanism of HPAI and LPAI introductions.

11. Result - Snow depth analysis

12. Result - Snow depth analysis
Case
Rank
(From
low
to
high)
Wilcoxon
P
value
1 26
out
of
56
0.90
2 21
out
of
56
0.66
3 40
out
of
56
0.50
4 27
out
of
54
1.00
5 54
out
of
56
0.12
6 49
out
of
56
0.21
7 11
out
of
56
0.29
8 4
out
of
55
0.14
Case 7 and 8 have lower snow depths than non-introduction years.
Other cases have average level of snow depths among all the year.

13. Conclusion and future direction
• The similar temporal patterns of Case 7 and the HPAI cases
from other locations suggest a universal climatic condition
that drives the occurrence of HPAI outbreak.
• Several weather indicators correlate with the timing of the
introductions.These indicators could help to predict the
timing of the next IAV introduction in turkey flocks.