1. Epidemiology Of Influenza Infection Among Pregnant Women And Children Under 6 Months In Mongolia, 2013/14 Season: A Prospective Cohort Study
L Chaw1, A Burmaa2, T Kamigaki1, Ch Urtnasan2, I Od3, G Nyamaa2, P Nymadawa2,4, H Oshitani1
1 Department of Virology, Tohoku University Graduate School of Medicine, Sendai, Japan
2 National Influenza Center, National Center of Communicable Diseases, Ulaanbaatar, Mongolia
3 Baganuur District, Ulaanbaatar, Mongolia
4Mongolian Academy of Medical Sciences, Ulaanbaatar, Mongolia

2. Introduction
Pregnant women and children under 6 months are known to have high risk for developing severe complications due to influenza, leading to hospitalizations
Maternal influenza vaccination could be one of the possible preventive measure for both groups
Important to know the disease burden at the community level, especially in countries with limited resources
Objective: To assess the influenza disease burden for the pregnant women and children under 6 months old in a community, by:
- Calculating incidence rate
- Identifying risk factors for infection
- Detecting hospitalised cases
Most of the previous studies on these 2 gps tend to focus on hospitalised cases
Few studies done at community level

3. Method Design: Prospective cohort study
Period: October 1st 2013 – April 30th 2014
Participants: All women, and children who are pregnant and less than 6 months old, respectively, during the study period
Place: Baganuur District, Ulaanbaatar, Mongolia
A mining town with quite high population density
Population: 27,440 (2012)  ½ are of reproductive age (15-44years)
4 FGPs (Family General Practitioner) provide free primary health care
Baganuur

4. Work flow in the field Baseline data collection Active follow-up
Pregnant women  Demographic, household member, O&G
Children <6 months  Demographic, newborn
End:
Apr 30th 2014
Start:
Oct 1st 2013
Oct 28th
Active follow-up
Via phone calls every 2 to 5 days
Naso-pharyngeal swabs collected and tested with rapid test kits (QuickNaviTM – Flu+RSV)
≥ 74% of samples were collected within 3 days of symptom onset
Eligible participants identified & enrolled at all 4 FGPs
Follow-up stops when:
Woman is not pregnant anymore,
Child reaches 6 months old,
Moves out of the district
ILI case definition: The sudden onset of fever of >38°C or feverish, with or without cough within the past 7 days

5. Temporal distribution of confirmed cases
Routine ILI surveillance
Pregnant women
Children <6 months
Title + x-axis & y-axis (+ note y-axis scale)
Distribution for preg women & children
For comparison, the case distribution among the general pop of Baganuur  epidemic start from early Jan till mid-Apr
Cases among preg women occur before Mar
Cases among infants occur till early April
Shows the general picture of the cases detected for both groups, now will talk in detail about each group separately..

6. Pregnant women
Result 1

7. Population Characteristics
Total pregnant women
ILI cases
p-value^
Mean age at enrolment
27.7 years
29.3 years
0.01*
(range)
( )
( )
Household structure (%)
0.03*
Apartment
298 (46.3)
67 (59.8)
Ger
235 (36.5)
33 (29.5)
Private house
110 (17.1)
12 (10.7)
Marital status (%)
0.02*
Married
355 (55.2)
77 (68.8)
Never married
270 (42.0)
34 (30.4)
Divorced/Separated
18 (2.8)
1 (0.9)
Education (%)
0.007*
Secondary school
14 (2.2)
4 (3.6)
High school
198 (30.8)
18 (16.1)
College
165 (25.7)
36 (32.1)
University
264 (41.1)
54 (48.2)
Trimester at enrolment(%)
<0.001*
1st
265 (41.2)
68 (60.7)
2nd
217 (33.7)
38 (33.9)
3rd
161 (25.0)
6 (5.4)
Reason for leaving study (%)
Gave birth
289 (44.9)
37 (33.0)
Medical complication
30 (4.7)
2 (1.8)
Moved out of Baganuur
31 (4.8)
Enrolled 643 women
112 ILI cases detected (17.4%)
Significant differences between total population & ILI cases observed in:
>85% of them stayed mainly in Baganuur throughout the study period
^All p-values calculated with Fisher’s Exact test, except for age (Student’s t-test used)

8. Virus positivity and Incidence rate
Pregnant women
ILI
Flu A
Flu B
RSV
Cases detected (n)
112 12 2
Virus positivity rate
12.1%
2.2%
Incidence rate
(per 1000 person-weeks)
13.1
1.4
0.2
Total person-weeks: 8561
(of follow-up)

9. Hospitalisation & risk factors for infection
No hospitalisations was observed among confirmed cases
No significant differences were found when compared with total population
Characteristics  
Total pregnant women
(n = 643)
Flu A +
(n = 11)
Flu B +
(n = 2)
RSV +
Mean age, years
27.7
30.2
33.1
28.7
(range)
( )
( )
( )
( )
Trimester stage at symptom onset 
1st
265 3 1
2nd
217 6
3rd
161 2
Hospitalised
6/11 Flu A cases got infected during their 2nd trimester
^All p-values calculated with Fisher’s Exact test, except for age (Student’s t-test used)

10. Children < 6 months
Result 2

11. Total children <6 months
Population Characteristics
Mainly healthy group of children
96.4% with normal birth weight
95.3% with no medical condition at birth
98.7% breastfed for >6 months
Enrolled 686 children
165 ILI cases detected (24.1%)
ILI cases were significantly older
Characteristics  
Total children <6 months
ILI cases
p-value^
Mean age
1.86 months
3.69 months
<0.001*
(range)
days
days
Male (%)
359 (52.3)
90 (54.5)
0.66
Reason for leaving study (%)
Reached 6 months old
377 (55.0)
81 (49.1)
Moved out of Baganuur
5 (0.7)
^All p-values calculated with Fisher’s Exact test, except for age (Student’s t-test used)

12. Virus positivity and Incidence rate
Children <6 months
ILI
Flu A
Flu B
RSV
Cases detected (n)
165 8 5 7
Virus positivity rate
4.8% 3%
4.2%
Incidence rate
(per 1000 person-weeks)
17.1
0.8
0.5
0.7
Total person-weeks: 9646
(of follow-up)

13. Hospitalisation & risk factors for infection
Characteristics 
Total children <6months
Flu A (n=8)
p-value^
Flu B+ (n=5)
RSV+ (n=7)
Mean age, months
1.86
4.8
<0.001*
4.6
0.043*
4.1
0.002*
(range, days)
Birthweight
0.26
1.0
0.027*
<2500g 25 1 2
>2500g
661 7 5
Term pregnancy
1.00
0.60
0.03*
Preterm 6
Early term
109 4
Full term
571 3
Medical condition at birth
0.31
0.038* No
654
Yes 30
Hospitalised
Mean age for confirmed cases were significantly higher
RSV cases tend to:
Have low birth weight,
Be from early term pregnancy,
Have medical condition at birth
No hospitalisations observed among confirmed cases
^All p-values calculated with Fisher’s Exact test, except for age (Student’s t-test used)

14. Summary & Discussion #1
Calculated the incidence rate among the 2 specific groups for one influenza season
Risk factors of infection:
For pregnant women,
Did not observe any significant differences among the confirmed cases
However, the ILI cases tend to have higher mean age, live in apartments, are married, and have higher education
For children < 6 months,
Confirmed cases were significantly older (i.e months old)
RSV cases tend to have low birth weight, of early term pregnancy, and have medical condition at birth
Incidence rate
(per 1000 person-weeks)
ILI
Flu A
Flu B
RSV
Pregnant women
13.1
1.4
0.2
Children < 6 months
17.1
0.8
0.5
0.7
Lower than what is found among children in Navajo & White Mountain Apache Indian reservations (Eick, et. al, 2011)
Our study = 2.44 per 1000 person-days (ILI IR)
Eick et. al = 7.2 per 1000 person-days (ILI IR) for infants born to unvaccinated women

15. Summary & Discussion #2
No hospitalisation from confirmed cases (for both groups)
Hence, no apparent severe outcomes for this influenza season
Positivity rate for the non-pregnant females in the reproductive age group were quite similar to our pregnant women group
Limitations:
Detecting symptomatic cases only
Use of rapid test kits
Unable to subtype influenza positive cases
Few number of cases detected
Passive surveillance of year old women in Baganuur,
ILI
Flu A
Flu B n
113 12 5
Positivity rate
10.6%
4.4%

16. Future direction Plan to also do multivariate analysis
May continue this study for another season
Comparing results from 2 seasons may provide more insight

17. Thank you!

18. Definitions Trimester stage: BMI Term pregnancy
1st : 0 to wks
2nd : to wks
3rd : to 42~ wks
BMI
<18.5 underweight
18.5 – normal
25.0 – 29.9 obese
>=30 very obese
Term pregnancy
Preterm <37 0/7 wks
Early term 37 0/7 – 38 6/7 wks
Full term >39 0/7 wks
Increase in birth rate for last 10 years (importance on maternal & child care)
¼ of all fatal A(H1N1)2009 pandemic cases in Mongolia were pregnant2
Nationwide surveillance detected mainly flu B (48%), followed by pandemic A/H1N1 (32%) and A/H3N2 (20%)