Surveillance and outbreak report
An outbreak of chickenpox in an asylum seeker centre in Italy: outbreak investigation and validity of reported chickenpox history, December 2015–May 2016 Francesco Vairo1,2,3, Virginia Di Bari1,3, Vincenzo Panella⁴, Giuseppe Quintavalle⁵, Saul Torchia⁵, Maria Cristina Serra⁵, Maria Teresa Sinopoli⁵, Maurizio Lopalco6,7, Giancarlo Ceccarelli⁶, Federica Ferraro², Sabrina Valle², Licia Bordi¹, Maria Rosaria Capobianchi¹, Vincenzo Puro1,2, Paola Scognamiglio1,2, Giuseppe Ippolito¹, the Outbreak Investigation Group⁸ 1. National Institute for Infectious Diseases INMI ‘L. Spallanzani’ IRCCS, Rome, Italy 2. Regional Service for Infectious Diseases Surveillance and Response (SERESMI), Latium Region, Rome, Italy 3. These authors contributed equally to the manuscript 4. Directorate of Health and Social Welfare, Latium Region, Rome, Italy 5. Local Public Health Unit ASL Roma 4, Latium Region, Rome, Italy 6. Sanitary Bureau of Asylum Seekers Center of Castelnuovo di Porto, Rome, Italy 7. Auxilium Società Cooperativa Sociale, Senise (Potenza), Italy 8. The members of the Outbreak Investigation Group are listed at the end of the article Correspondence: Paola Scognamiglio (
[email protected]) Citation style for this article: Vairo Francesco, Di Bari Virginia, Panella Vincenzo, Quintavalle Giuseppe, Torchia Saul, Serra Maria Cristina, Sinopoli Maria Teresa, Lopalco Maurizio, Ceccarelli Giancarlo, Ferraro Federica, Valle Sabrina, Bordi Licia, Capobianchi Maria Rosaria, Puro Vincenzo, Scognamiglio Paola, Ippolito Giuseppe, the Outbreak Investigation Group. An outbreak of chickenpox in an asylum seeker centre in Italy: outbreak investigation and validity of reported chickenpox history, December 2015–May 2016. Euro Surveill. 2017;22(46):pii=17-00020. https://doi.org/10.2807/1560-7917.ES.2017.22.46.17-00020 Article submitted on 05 Jan 2017 / accepted on 23 May 2017 / published on 16 Nov 2017
An outbreak of chickenpox occurred between December 2015 and May 2016 among asylum seekers in a reception centre in Latium, Italy. We describe the epidemiological and laboratory investigations, control measures and validity of reported history of chickenpox infection. Serological screening of all residents and incoming asylum seekers was performed, followed by vaccine offer to all susceptible individuals without contraindication. Forty-six cases were found and 41 were associated with the outbreak. No complications, hospitalisations or deaths occurred. Serological testing was performed in 1,278 individuals and 169 were found to be susceptible, with a seroprevalence of 86.8%. A questionnaire was administered to 336 individuals consecutively attending the CARA health post to collect their serological result. The sensitivity, specificity and the positive and negative predictive value (PPV and NPV) of the reported history of chickenpox were 45.0%, 76.1%, 88.3% and 25.6%, respectively. We observed an increasing trend for the PPV and decreasing trend for the NPV with increasing age. Our report confirms that, in the asylum seeker population, chickenpox history is not the optimal method to identify susceptible individuals. Our experience supports the need for additional prevention and control measures and highlights the importance of national and local surveillance systems for reception centres.
Background
The International Organisation for Migration estimated that 345,440 migrants and refugees entered Europe by sea in 2016 up to 22 November (171,264 in Greece www.eurosurveillance.org
and 168,542 in Italy) [1]. In March 2016, the Italian Ministry of Interior estimated that ca 111,000 migrants were living in Italy and most of them were asylum seekers living in collective housing facilities [2]. The term ‘migrant’ as used in this paper covers also refugees and asylum seekers. The migrant population is usually made up of young and healthy people, who are at risk for infectious diseases as a consequence of the difference in infectious disease prevalence between their countries of origin and the hosting countries as well as the conditions they experience during migration [3]. An additional risk is posed by the specific challenges faced by collective housing facilities in preventing and controlling communicable disease transmission in ‘semi-open’ communities [4] with an often higher than affordable number of people entering the facilities. Among the infectious diseases potentially affecting the migrant population, chickenpox (mainly transmitted through the airborne route) is characterised by a high potential of spread in closed and semi-open communities, and by a slightly lower seroprevalence in tropical compared with temperate areas: In temperate regions, ca 95% of people 12 years and older are immune [5,6] while in tropical areas, seroprevalence in adults varies from 93.5% to 70%, with a proportion of susceptible individuals ranging from 6.5% to 30% [7,8]. Several outbreaks of chickenpox among asylum seeker populations have been reported in the literature [7,9-11]. Vaccination of susceptible individuals was a key intervention for outbreak control [6,7].
1
Figure Epidemiological curve and outbreak control measures, Italy, December 2015−May 2016 (n = 46) Patients isolation
7
Serological screening 6
VD 1
Number of cases
5
VD 2
VD 3
4
3
2
1
0 18 Jul
11 Jul
04 Jul
27 Jun
20 Jun
13 Jun
06 Jun
30 May
23 May
16 May
09 May
02 May
25 Apr
11 Apr
18 Apr
04 Apr
28 Mar
21 Mar
14 Mar
07 Mar
29 Feb
22 Feb
15 Feb
08 Feb
01 Feb
25 Jan
18 Jan
11 Jan
04 Jan
28 Dec
21 Dec
14 Dec
07 Dec
23 Nov
2015
2016 Week of symptom onset
VD: vaccination day. Green dots: cases involved in two probably separate cases in early December 2015; yellow dots: probably imported cases.
In 2011, the Italian Ministry of Health (MoH) has implemented a syndromic surveillance system in collective housing facilities in order to rapidly detect potential public health emergencies [12]. The syndromic surveillance system works in parallel with the surveillance system for notifiable infectious diseases which was strengthened in 2015 in the Latium region to respond to the expected high influx of people visiting Rome for the one-year Jubilee 2015–16, one of the most important Catholic events that sees pilgrims gather in Rome to pray) [13]. Within the framework of the enhanced surveillance, the Lazio Regional Service for the epidemiology and control for infectious diseases (SERESMI) was alerted in January 2016 by the syndromic surveillance system of a cluster of ‘fever with rash syndrome’ among the population living in an asylum seekers centre (CARA), followed by notifications of five cases of chickenpox. The CARA health staff and the local public health authority promptly implemented all routine control measures (isolation of cases, contact tracing and vaccination of close contacts with negative chickenpox history). Despite these control interventions, 25 more cases were notified during the following 3 months. In April 2016, new control measures were recommended and implemented: serological screening of all residents 2
and incoming asylum seekers followed by vaccine offer to all susceptible individuals without contraindications (immunodepression, pregnancy, etc). During the implementation phase of the additional control measures, 16 new cases were notified. The last case was notified on 17 May 2016. This report describes the epidemiological and laboratory investigations and the control measures implemented during the outbreak. In order to evaluate the performance of reported history to assess immune status, a questionnaire was administered to a subgroup of serologically screened individuals.
Methods Setting
CARA centres are facilities hosting newly arriving migrants who seek international protection; they were established following the reform of the asylum law, enacted to implement two European Union (EU) directives [14,15]. They are under the authority of the Ministry of Interior through the Prefectures which entrust the management to private or non-governmental bodies. The CARA involved in the outbreak is located in Rome and is the largest in the Latium Region. Before the outbreak, the population residing in the centre was made www.eurosurveillance.org
Table 1 Socio-demographic characteristics of serologically screened individuals, by chickenpox immune status, Italy, December 2015−May 2016 (n = 1,278) Immune (n = 1,109)
Susceptible (n = 169)
Total population (n = 1,278)
n
%
n
%
n
%
Male
909
82.0
139
82.2
1,048
82.0
Female
198
17.8
30
17.8
228
17.8
Missing
2
0.2
0
0
2
0.2
p value
Sex
Age (years) as mean (± SD) Length of stay in the centre in days, median (IQR)
0.96 a
25 (± 7)
24 (± 5)
25 (± 7)
0.02 b
5 (1 – 222)
4 (1 – 222)
5 (1 – 222)
0.81
Country of birth Eritrea
646
58.3
109
64.5
755
59.1
Nigeria
71
6.4
14
8.3
85
6.7
The Gambia
65
5.9
4
2.4
69
5.4
Mali
59
5.3
9
5.3
68
5.3
Pakistan
47
4.2
11
6.5
58
4.5
Senegal
53
4.8
5
3.0
58
4.5
Guinea
35
3.2
2
1.2
37
2.9
Bangladesh
30
2.7
4
2.4
34
2.7
Ghana
26
2.3
4
2.4
30
2.3
Syria
23
2.1
1
0.6
24
1.9
Côte d’Ivoire
12
1.1
2
1.2
14
1.1
Sudan
9
0.8
2
1.2
11
0.9
Ethiopia
10
0.9
0
0
10
0.8
Togo
6
0.5
0
0
6
0.5
Guinea-Bissau
4
0.4
0
0
4
0.3
Burkina Faso
2
0.2
0
0
2
0.2
Palestine c
2
0.2
0
0
2
0.2
Benin
1
0.1
0
0
1
0.1
Cameroon
1
0.1
0
0
1
0.1
Congo
1
0.1
0
0
1
0.1
India
0
0
1
0.6
1
0.1
Iraq
1
0.1
0
0
1
0.1
Liberia
1
0.1
0
0
1
0.1
Central African Republic
0
0
1
0.6
1
0.1
Sierra Leone
1
0.1
0
0
1
0.1
Sri Lanka
1
0.1
0
0
1
0.1
Missing
2
0.2
0
0
2
0.2
0.65 a
Geographic region East Africa
656
59.2
109
64.5
756
59.9
West Africa
336
30.3
40
23.7
376
29.4
South Asia
78
7.0
16
9.5
94
7.4
West Asia
26
2.3
3
1.8
27
2.1
Central Africa
11
1.0
1
0.6
14
1.1
Missing
2
0.2
0
0
2
0.2
0.06 a
IQR: interquartile range; SD: standard deviation. Chi-squared test. b t-test. c This designation shall not be construed as recognition of a State of Palestine and is without prejudice to the individual positions of the Member States on this issue. a
www.eurosurveillance.org
3
Table 2 Characteristics of individuals included in the validity analysis, by chickenpox serological immune status and chickenpox history, Italy, December 2015−May 2016 (n = 336) Questionnaire
Serological test Total
Immune n
%
Susceptible n
pa
%
Immune n
Susceptible
%
n
%
106
39.6
162
60.4
30
44.8
37
55.2
1
100
0
0
pa
Sex Male
268
79.8
221
82.5
47
17.5
Female
67
19.9
47
70.2
20
29.9
Missing
1
0.3
1
100
0
0
24.5
6.1
25.5 (6.3)
East Africa
223
66.4
177
79.4
46
20.6
100
44.8
123
55.2
West Africa
79
23.5
67
84.8
12
15.2
23
29.1
56
70.9
South Asia
18
5.4
11
61.1
7
38.9
7
38.9
11
61.1
West Asia
5
1.5
5
100
0
0
3
60.0
2
40.0
Central Africa
10
3.0
8
80.0
2
20.0
3
30.0
7
70.0
Missing
1
0.3
1
100
0
0
1
100
0
0
Urban
155
46.1
132
85.2
23
14.8
82
52.9
73
47.1
Rural
165
49.1
122
73.9
43
26.1
49
29.7
116
70.3
Missing
16
4.8
15
93.7
1
6.3
6
37.5
10
62.5
Age (years) as mean (± SD)
23.3(4.7)
0.02 0.001
26.6(6.8)
23.9(5.2)
0.36
