Pathfinder
Editor, Senior Moderator
DISCLAIMER
This paper was submitted to the Bulletin of the World Health Organization and was posted to the
Zika open site, according to the protocol for public health emergencies for international concern as
described in Christopher Dye et al. (http://dx.doi.org/10.2471/BLT.16.170860).
The information herein is available for unrestricted use, distribution and reproduction in any
medium, provided that the original work is properly cited as indicated by the Creative Commons
Attribution 3.0 Intergovernmental Organizations licence (CC BY IGO 3.0).
RECOMMENDED CITATION
Craig AT, Butler MT, Pastore R, Paterson B, Durrheim DN. Update on Zika virus transmission in the
Pacific islands, 2007 to February 2016 and failure of acute flaccid paralysis surveillance to signal Zika
emergence in this setting [Submitted]. Bull World Health Organ E-pub: 19 Feb 2016. doi:
http://dx.doi.org/10.2471/BLT.16.171892
Update on Zika virus transmission in the Pacific islands,
2007 to February 2016 and failure of acute flaccid paralysis
surveillance to signal Zika emergence in this setting
Adam T Craig,a
Michelle T Butler,b
Roberta Pastmore,c
Beverley J
Paterson,a
David N Durrheima
a
Hunter Medical Research Institute, University of Newcastle, 20 Keir Avenue, Newtown, New South
Wales, 2193, Australia.
b
Population Health, Hunter New England Health, Tarree, Australia.
c
Division of Communicable Disease, Regional Office for the Western Pacific, World Health
Organization, Manila, Philippines.
Correspondence to Adam Craig (email: adam@adamcraig.com.au).
(Submitted: 18 February 2016 ? Published online: 19 February 2016)
ABSTRACT
Objective: To describe the distribution and magnitude of Zika virus (ZIKV) infections
reported in the Pacific islands from 2007 to February 2016; and explore the utility of
routine acute flaccid paralysis (AFP) surveillance to detect ZIKV emergence.
Method: We searched for evidence of ZIKV cases and outbreaks in the Pacific using
a PubMed search, reviewed Pacific peer communication channels and through
personal communication with relevant WHO staff. Routine acute flaccid paralysis
reporting data from 2000 to 2015 was reviewed to determine whether unexpected
surveillance exceedances correlated with ZIKV emergence in specific Pacific island
countries.
Findings: We report nine ZIKV outbreaks in eight Pacific islands countries and
areas (Yap State, Federal States of Micronesia (2007), French Polynesia (2013-14),
Cook Islands (2014), Easter Island (2014), New Caledonia (2014 and 2015),
Solomon Islands (2015) Tonga (2016) and American Samoa (2016), and a further
three Pacific countries that detected cases (but have not reported domestic
transmission): Vanuatu (2015), Fiji (2015), and Samoa (2015). Despite the reported
increase in Guillain-Barre syndrome (AFP) in Latin America, review of fluctuations in
detection rates in Pacific Islands found no correlation with ZIKV emergence.
Conclusion: Although no spatial correlation between AFP surveillance data and
reported Zika infections was found in the Pacific island context we recommend that
the utility of such a surveillance strategy be further tested in countries that are
vulnerable to ZIKV outbreak and have large populations under the age of 15 years.
INTRODUCTION
In the past weeks, the world has mobilised efforts to tackle Zika virus (ZIKV), the
latest threat to global health security, which is currently spreading rapidly in the
Americas [1,2]. Worldwide concern in response to increasing evidence that ZIKV
infection may be associated with congenital malformations and autoimmuneneurological
presentations, including microcephaly, cranial nerve dysfunction, and
Guillain-Barr? Syndrome (GBS) [1,3?11] has raised alarm among public health
authorities resulting on 1 February 2016 in the World Health Organization (WHO)
declaring the event a Public Health Emergency of International Concern [10].
The first human outbreak of ZIKV was documented in the Pacific ? in Yap State,
Federal States of Micronesia (FSM) ? in April 2007 [12]. Since this outbreak 10 other
Pacific island countries and areas 1
have reported domestic transmission of Zika
including: French Polynesia (2013-14), Cook Islands (2014), Easter Island (2014),
New Caledonia (2014 and 2015), Solomon Islands (2015), Vanuatu (2015), Fiji
(2015), Samoa (2015), and - at the time of writing - the Kingdom of Tonga (2016),
and American Samoa (2016) [13?21].This paper provides an update on ZIKV
transmission in the Pacific islands from 2007 to February 2016. The paper adds
Pacific-specific detail to the recently published timeline of global Zika transmission by
Kindhauser et al (2006) and supplements earlier (mid-epidemic) reports by Roth et al
[14] and Musso et al [13,17]. In addition, routinely reported acute flaccid paralysis
(AFP) data from 2000 to 2015 was reviewed to determine whether unexpected
1
For the purpose of this paper we have adopted the Western Pacific Regional Office of the WHO?s grouping of
countries and areas that fall within the grouping of ?Pacific islands?. These include: American Samoa, the Cook
Islands, the Federal States of Micronesia, Fiji, French Polynesia, Guam, Kiribati, the Marshall Islands, Nauru,
New Caledonia, Niue, the Commonwealth of the Northern Marianas Islands, Palau, Samoa, the Solomon
Islands, Tokelau, Tonga, Tuvalu, Vanuatu and Wallis and Futuna. Further, for the purpose of this paper Easter
Island (an area of Chile) has been included.
surveillance exceedances correlated with ZIKV emergence in affected Pacific island
countries and areas.
METHODS
We sought to identify published and unpublished information on human Zika cases
and outbreaks in the Pacific island from 2007 to February 2016 (time of writing). We
conducted a literature search using the search terms ?Zika? and ?ZIKV? in PubMed
and reviewed identified papers for their relevance to events in the Pacific island; we
reviewed and extracted event-relevant information from PacNet 2
posts
(http://goo.gl/zSOaeO) and WHO?s Weekly Pacific Surveillance Reports
(lhttp://goo.gl/xrIStN); and to triangulate and update information on known events,
and to identify and collect information on undocumented events we consulted WHO?s
Division of Pacific Technical Support in Fiji.
We reviewed routinely reported AFP data for Pacific island countries and areas from
2000 to 2015 and compared unexpected surveillance exceedances with ZIKV
emergence in the islands to identify any correlation. We conducted a Poisson
probability test to calculate p-values at the 5% significance level for years where
more cases were reported than expected.
2
PacNet is the discussion listserv of the Pacific Public Health Surveillance Network. PacNet?s main function is
to serve as an outbreak communication and alert mechanism, and to support outbreak preparedness in the
Pacific region [18].
FINDINGS
Prior to 2007 sporadic human cases of ZIKV had been reported in countries
spanning equatorial Africa and Asia but no outbreaks in humans had been
documented [2]. Hayes (2009) and Kindhauser et al (2016) provide an account of
these cases [22,23].
In 2007, the first outbreak of ZIKV in humans was identified by physicians on Yap
Island in Yap State, FSM. The outbreak investigation identified 185 suspected cases
of which 49 were confirmed. Investigators estimated the outbreak attack rate to be
73% (95%CI: 68-77%). All cases experienced mild symptoms typically associated
with Zika infection ? rash (90%), fever (65%), arthralgia (65%), and conjunctivitis
(55%). No hospitalisation, haemorrhagic signs or associated deaths were reported
[12].
No further Zika cases were detected in the Pacific until October 2013 when an
explosive outbreak occurred in French Polynesia [20]. The French Polynesian
outbreak ? confirmed in 383 cases ? lasted six months (October 2013 to March
2014) and is estimated to have infected more than 32,000 cases or 86% (95% CI:
75-93%) of the population [24]. Kucharski and colleagues (2016) estimate the
outbreak Re at between 1.9 and 3.1 [24]. A number of cases infected with ZIKV
during the outbreak developed severe and rare neurological and auto-immune
conditions including 42 cases of GBS and 18 foetal or new born cases with unusual
and severe neurological conditions. Of the 18 foetal and new born cases ten were
diagnosed with microcephaly and severe brain lesions, and eight had anatomical or
dysfunctional neurological abnormalities [4,24,25]. Suspicion was raised (and the
hypothesis continues to be tested, although not yet proven) that ZIKV infection was
the cause of these sequelae. Phylogenetic analyses demonstrated that the outbreak
strain was closely related to the outbreak strain in Yap during 2007 [20].
Given travel pathways and close geographic and cultural ties, the outbreak in French
Polynesia is suspected to have been the source of subsequent outbreaks on Easter
Island (January to May 2014; 89 suspected cases of which 51 were confirmed) [16],
in New Caledonia (January to July 2014, more than 1,385 confirmed cases [21] and
January to May 2015, 82 confirmed cases [19]); and on the Cook Islands (February
to May 2014; 932 suspected cases of which 54 were confirmed [15]). One case in
the 2013 New Caledonian outbreak was reported to have developed GBS [26]; no
other severe illness was reported from the outbreaks.
In 2015/16 two Pacific island countries reported autochthonous transmission of
ZIKV: Solomon Islands (February to May 2015; 324 suspected cases of which 5
have been confirmed) and Tonga (January 2016 and ongoing; 549 suspected of
which 2 have been confirmed). One case in the Solomon Islands outbreak was
reported to have developed probable GBS.
Five other Pacific islands reported sporadic (non-autochthonous) Zika cases in
2015/16: Vanuatu (February to March 2015, 1 confirmed case), Fiji (August 2015, 2
confirmed cases), Samoa (September to October 2015, 3 confirmed cases), and
American Samoa (February 2016 and ongoing; 99 suspected cases of which 4 are
confirmed) [15,18] (TABLE 1). A number of imported cases (mainly from the Pacific
islands) have been detected in Australia [27] and New Zealand [28] including one
traveller returning to New Zealand from Tonga that developed GBS symptoms [29].
To test a hypothesis that AFP data (routinely collected as a criterion for performance
of the Global Polio Eradication Initiative [30,31]) may serve as a useful surveillance
strategy for the detection of emergence of ZIKV in previously unaffected countries
we compared Pacific islands? data on AFP case from 2000 to 2015 with known Zika
transmission. While statically excess AFP cases were notified from aggregated
Pacific islands? data in 2000 (p=<0.004), 2006 (p=<0.001), 2009 (p=<0.008) and
2014 (p=<0.04) statistically significant country level case excesses was only found
for the Solomon Islands in 2015 (p=<0.001) (FIGURE 1).
DISCUSSION
We present an epidemiological review of ZIKV activity in the Pacific islands from
2007 to February 2016. As infection with ZIKV typically causes mild symptoms that
overlap with clinical features of dengue and chikungunya infection (both of which
have been circulating in the Pacific in past years [14]), and due to the limited
surveillance and diagnostic capacity of most Pacific islands we believe that ongoing
and undetected ZIKV transmission in other Pacific island countries and areas is
highly probable.
The observation in French Polynesia and the Americas that severe clinical
complications are possibly associated with Zika infection highlights the need to
strengthen surveillance for this emerging virus, and, in the event of outbreaks
establish rigorous clinical monitoring to detect neurological and other unusual clinical
manifestations.
Given the proposed link between ZIKV infection and GBS we hypothesised that AFP
surveillance, routinely conducted in all countries for children under the age of 15
years as part of the Global Polio Eradication Program?s quality monitoring activity
[30], may serve as a useful, convenient and cost-effective surveillance strategy for
detecting the emergence of ZIKV in previously unaffected areas. In the Americas
(Columbia and Venezuela) it appears that enhanced surveillance after ZIKV
introduction is finding an increased rate of GBS cases [32]; this should lead to an
increase in AFP reports. While we found this strategy was not effective in Pacific
islands countries where populations are small (and hence expected number of AFP
cases is low, often <1 per year) and surveillance data quality inadequate, we suggest
that the utility of this surveillance strategy be explored in countries vulnerable to Zika
transmission and that have large populations under 15 years of age.
The Solomon Islands was the only country where a statistically significant increase in
AFP cases correlated with the emergence of Zika virus. This could represent
confirmation of the utility of increased AFP detection for signalling the appearance of
Zika virus, or reflect more sensitive public health surveillance following a major
cyclone, or be a chance finding given that it was the only country where this
occurred. This observation reinforces the need to explore AFP surveillance as a
strategy for ZIKV detection in other settings.
The transmission of ZIKV in the resource-limited Pacific island context poses unique
challenges for public health preparedness and outbreak surveillance. Typically mild
symptoms similar to dengue and chikungunya, limited coverage and sensitivity of
existing early warning surveillance systems, limited capacity to investigate and verify
surveillance signals, widely dispersed populations, poor communication, and
inadequately resourced health systems all conspire to make timely and accurate
detection of ZIKV incursions problematic. Further investigation is required to
determine what factors ? in the islands? setting - influence the intensity and speed of
ZIKV transmission, and ability of early warning surveillance to detect cases. In this
context, it is possible that GBS cases, which remain relatively uncommon, have been
missed due to the small case numbers and poor surveillance quality.
WHO recommends that all countries maintain a heightened awareness and build
capacity to detect and confirm ZIKV cases; ensure health system preparedness to
respond to a possible increased demand for specialised care (for microcephaly and
neurological syndromes); strengthen antenatal care; and introduce public health
measures to reduce risk of ZIKV spread and infection [9,10].
CONCLUSION
Since the first transmission of ZIKV outside Africa and Asia was documented in an
outbreak in Yap State, FSM in 2007, transmission has been reported in 10 other
Pacific island countries and areas: French Polynesia (2013-14), Cook Islands (2014),
Easter Island (2014), New Caledonia (2014-15), Solomon Islands (2015), Vanuatu
(2015), Fiji (2015), Samoa (2015), and - at the time of writing - the Kingdom of Tonga
(2016) and American Samoa (2016) causing large outbreaks in some. Infection has
being associated with severe clinical complications in French Polynesia. We found
no spatial-temporal correlation between routinely collected AFP data and ZIKV
emergence in previously unaffected Pacific island countries. We suggest the utility of
such a surveillance strategy be further tested in countries that are vulnerable to ZIKV
outbreak and have large populations under the age of 15 years.
http://www.who.int/bulletin/online_first/16-171892.pdf?ua=1
This paper was submitted to the Bulletin of the World Health Organization and was posted to the
Zika open site, according to the protocol for public health emergencies for international concern as
described in Christopher Dye et al. (http://dx.doi.org/10.2471/BLT.16.170860).
The information herein is available for unrestricted use, distribution and reproduction in any
medium, provided that the original work is properly cited as indicated by the Creative Commons
Attribution 3.0 Intergovernmental Organizations licence (CC BY IGO 3.0).
RECOMMENDED CITATION
Craig AT, Butler MT, Pastore R, Paterson B, Durrheim DN. Update on Zika virus transmission in the
Pacific islands, 2007 to February 2016 and failure of acute flaccid paralysis surveillance to signal Zika
emergence in this setting [Submitted]. Bull World Health Organ E-pub: 19 Feb 2016. doi:
http://dx.doi.org/10.2471/BLT.16.171892
Update on Zika virus transmission in the Pacific islands,
2007 to February 2016 and failure of acute flaccid paralysis
surveillance to signal Zika emergence in this setting
Adam T Craig,a
Michelle T Butler,b
Roberta Pastmore,c
Beverley J
Paterson,a
David N Durrheima
a
Hunter Medical Research Institute, University of Newcastle, 20 Keir Avenue, Newtown, New South
Wales, 2193, Australia.
b
Population Health, Hunter New England Health, Tarree, Australia.
c
Division of Communicable Disease, Regional Office for the Western Pacific, World Health
Organization, Manila, Philippines.
Correspondence to Adam Craig (email: adam@adamcraig.com.au).
(Submitted: 18 February 2016 ? Published online: 19 February 2016)
ABSTRACT
Objective: To describe the distribution and magnitude of Zika virus (ZIKV) infections
reported in the Pacific islands from 2007 to February 2016; and explore the utility of
routine acute flaccid paralysis (AFP) surveillance to detect ZIKV emergence.
Method: We searched for evidence of ZIKV cases and outbreaks in the Pacific using
a PubMed search, reviewed Pacific peer communication channels and through
personal communication with relevant WHO staff. Routine acute flaccid paralysis
reporting data from 2000 to 2015 was reviewed to determine whether unexpected
surveillance exceedances correlated with ZIKV emergence in specific Pacific island
countries.
Findings: We report nine ZIKV outbreaks in eight Pacific islands countries and
areas (Yap State, Federal States of Micronesia (2007), French Polynesia (2013-14),
Cook Islands (2014), Easter Island (2014), New Caledonia (2014 and 2015),
Solomon Islands (2015) Tonga (2016) and American Samoa (2016), and a further
three Pacific countries that detected cases (but have not reported domestic
transmission): Vanuatu (2015), Fiji (2015), and Samoa (2015). Despite the reported
increase in Guillain-Barre syndrome (AFP) in Latin America, review of fluctuations in
detection rates in Pacific Islands found no correlation with ZIKV emergence.
Conclusion: Although no spatial correlation between AFP surveillance data and
reported Zika infections was found in the Pacific island context we recommend that
the utility of such a surveillance strategy be further tested in countries that are
vulnerable to ZIKV outbreak and have large populations under the age of 15 years.
INTRODUCTION
In the past weeks, the world has mobilised efforts to tackle Zika virus (ZIKV), the
latest threat to global health security, which is currently spreading rapidly in the
Americas [1,2]. Worldwide concern in response to increasing evidence that ZIKV
infection may be associated with congenital malformations and autoimmuneneurological
presentations, including microcephaly, cranial nerve dysfunction, and
Guillain-Barr? Syndrome (GBS) [1,3?11] has raised alarm among public health
authorities resulting on 1 February 2016 in the World Health Organization (WHO)
declaring the event a Public Health Emergency of International Concern [10].
The first human outbreak of ZIKV was documented in the Pacific ? in Yap State,
Federal States of Micronesia (FSM) ? in April 2007 [12]. Since this outbreak 10 other
Pacific island countries and areas 1
have reported domestic transmission of Zika
including: French Polynesia (2013-14), Cook Islands (2014), Easter Island (2014),
New Caledonia (2014 and 2015), Solomon Islands (2015), Vanuatu (2015), Fiji
(2015), Samoa (2015), and - at the time of writing - the Kingdom of Tonga (2016),
and American Samoa (2016) [13?21].This paper provides an update on ZIKV
transmission in the Pacific islands from 2007 to February 2016. The paper adds
Pacific-specific detail to the recently published timeline of global Zika transmission by
Kindhauser et al (2006) and supplements earlier (mid-epidemic) reports by Roth et al
[14] and Musso et al [13,17]. In addition, routinely reported acute flaccid paralysis
(AFP) data from 2000 to 2015 was reviewed to determine whether unexpected
1
For the purpose of this paper we have adopted the Western Pacific Regional Office of the WHO?s grouping of
countries and areas that fall within the grouping of ?Pacific islands?. These include: American Samoa, the Cook
Islands, the Federal States of Micronesia, Fiji, French Polynesia, Guam, Kiribati, the Marshall Islands, Nauru,
New Caledonia, Niue, the Commonwealth of the Northern Marianas Islands, Palau, Samoa, the Solomon
Islands, Tokelau, Tonga, Tuvalu, Vanuatu and Wallis and Futuna. Further, for the purpose of this paper Easter
Island (an area of Chile) has been included.
surveillance exceedances correlated with ZIKV emergence in affected Pacific island
countries and areas.
METHODS
We sought to identify published and unpublished information on human Zika cases
and outbreaks in the Pacific island from 2007 to February 2016 (time of writing). We
conducted a literature search using the search terms ?Zika? and ?ZIKV? in PubMed
and reviewed identified papers for their relevance to events in the Pacific island; we
reviewed and extracted event-relevant information from PacNet 2
posts
(http://goo.gl/zSOaeO) and WHO?s Weekly Pacific Surveillance Reports
(lhttp://goo.gl/xrIStN); and to triangulate and update information on known events,
and to identify and collect information on undocumented events we consulted WHO?s
Division of Pacific Technical Support in Fiji.
We reviewed routinely reported AFP data for Pacific island countries and areas from
2000 to 2015 and compared unexpected surveillance exceedances with ZIKV
emergence in the islands to identify any correlation. We conducted a Poisson
probability test to calculate p-values at the 5% significance level for years where
more cases were reported than expected.
2
PacNet is the discussion listserv of the Pacific Public Health Surveillance Network. PacNet?s main function is
to serve as an outbreak communication and alert mechanism, and to support outbreak preparedness in the
Pacific region [18].
FINDINGS
Prior to 2007 sporadic human cases of ZIKV had been reported in countries
spanning equatorial Africa and Asia but no outbreaks in humans had been
documented [2]. Hayes (2009) and Kindhauser et al (2016) provide an account of
these cases [22,23].
In 2007, the first outbreak of ZIKV in humans was identified by physicians on Yap
Island in Yap State, FSM. The outbreak investigation identified 185 suspected cases
of which 49 were confirmed. Investigators estimated the outbreak attack rate to be
73% (95%CI: 68-77%). All cases experienced mild symptoms typically associated
with Zika infection ? rash (90%), fever (65%), arthralgia (65%), and conjunctivitis
(55%). No hospitalisation, haemorrhagic signs or associated deaths were reported
[12].
No further Zika cases were detected in the Pacific until October 2013 when an
explosive outbreak occurred in French Polynesia [20]. The French Polynesian
outbreak ? confirmed in 383 cases ? lasted six months (October 2013 to March
2014) and is estimated to have infected more than 32,000 cases or 86% (95% CI:
75-93%) of the population [24]. Kucharski and colleagues (2016) estimate the
outbreak Re at between 1.9 and 3.1 [24]. A number of cases infected with ZIKV
during the outbreak developed severe and rare neurological and auto-immune
conditions including 42 cases of GBS and 18 foetal or new born cases with unusual
and severe neurological conditions. Of the 18 foetal and new born cases ten were
diagnosed with microcephaly and severe brain lesions, and eight had anatomical or
dysfunctional neurological abnormalities [4,24,25]. Suspicion was raised (and the
hypothesis continues to be tested, although not yet proven) that ZIKV infection was
the cause of these sequelae. Phylogenetic analyses demonstrated that the outbreak
strain was closely related to the outbreak strain in Yap during 2007 [20].
Given travel pathways and close geographic and cultural ties, the outbreak in French
Polynesia is suspected to have been the source of subsequent outbreaks on Easter
Island (January to May 2014; 89 suspected cases of which 51 were confirmed) [16],
in New Caledonia (January to July 2014, more than 1,385 confirmed cases [21] and
January to May 2015, 82 confirmed cases [19]); and on the Cook Islands (February
to May 2014; 932 suspected cases of which 54 were confirmed [15]). One case in
the 2013 New Caledonian outbreak was reported to have developed GBS [26]; no
other severe illness was reported from the outbreaks.
In 2015/16 two Pacific island countries reported autochthonous transmission of
ZIKV: Solomon Islands (February to May 2015; 324 suspected cases of which 5
have been confirmed) and Tonga (January 2016 and ongoing; 549 suspected of
which 2 have been confirmed). One case in the Solomon Islands outbreak was
reported to have developed probable GBS.
Five other Pacific islands reported sporadic (non-autochthonous) Zika cases in
2015/16: Vanuatu (February to March 2015, 1 confirmed case), Fiji (August 2015, 2
confirmed cases), Samoa (September to October 2015, 3 confirmed cases), and
American Samoa (February 2016 and ongoing; 99 suspected cases of which 4 are
confirmed) [15,18] (TABLE 1). A number of imported cases (mainly from the Pacific
islands) have been detected in Australia [27] and New Zealand [28] including one
traveller returning to New Zealand from Tonga that developed GBS symptoms [29].
To test a hypothesis that AFP data (routinely collected as a criterion for performance
of the Global Polio Eradication Initiative [30,31]) may serve as a useful surveillance
strategy for the detection of emergence of ZIKV in previously unaffected countries
we compared Pacific islands? data on AFP case from 2000 to 2015 with known Zika
transmission. While statically excess AFP cases were notified from aggregated
Pacific islands? data in 2000 (p=<0.004), 2006 (p=<0.001), 2009 (p=<0.008) and
2014 (p=<0.04) statistically significant country level case excesses was only found
for the Solomon Islands in 2015 (p=<0.001) (FIGURE 1).
DISCUSSION
We present an epidemiological review of ZIKV activity in the Pacific islands from
2007 to February 2016. As infection with ZIKV typically causes mild symptoms that
overlap with clinical features of dengue and chikungunya infection (both of which
have been circulating in the Pacific in past years [14]), and due to the limited
surveillance and diagnostic capacity of most Pacific islands we believe that ongoing
and undetected ZIKV transmission in other Pacific island countries and areas is
highly probable.
The observation in French Polynesia and the Americas that severe clinical
complications are possibly associated with Zika infection highlights the need to
strengthen surveillance for this emerging virus, and, in the event of outbreaks
establish rigorous clinical monitoring to detect neurological and other unusual clinical
manifestations.
Given the proposed link between ZIKV infection and GBS we hypothesised that AFP
surveillance, routinely conducted in all countries for children under the age of 15
years as part of the Global Polio Eradication Program?s quality monitoring activity
[30], may serve as a useful, convenient and cost-effective surveillance strategy for
detecting the emergence of ZIKV in previously unaffected areas. In the Americas
(Columbia and Venezuela) it appears that enhanced surveillance after ZIKV
introduction is finding an increased rate of GBS cases [32]; this should lead to an
increase in AFP reports. While we found this strategy was not effective in Pacific
islands countries where populations are small (and hence expected number of AFP
cases is low, often <1 per year) and surveillance data quality inadequate, we suggest
that the utility of this surveillance strategy be explored in countries vulnerable to Zika
transmission and that have large populations under 15 years of age.
The Solomon Islands was the only country where a statistically significant increase in
AFP cases correlated with the emergence of Zika virus. This could represent
confirmation of the utility of increased AFP detection for signalling the appearance of
Zika virus, or reflect more sensitive public health surveillance following a major
cyclone, or be a chance finding given that it was the only country where this
occurred. This observation reinforces the need to explore AFP surveillance as a
strategy for ZIKV detection in other settings.
The transmission of ZIKV in the resource-limited Pacific island context poses unique
challenges for public health preparedness and outbreak surveillance. Typically mild
symptoms similar to dengue and chikungunya, limited coverage and sensitivity of
existing early warning surveillance systems, limited capacity to investigate and verify
surveillance signals, widely dispersed populations, poor communication, and
inadequately resourced health systems all conspire to make timely and accurate
detection of ZIKV incursions problematic. Further investigation is required to
determine what factors ? in the islands? setting - influence the intensity and speed of
ZIKV transmission, and ability of early warning surveillance to detect cases. In this
context, it is possible that GBS cases, which remain relatively uncommon, have been
missed due to the small case numbers and poor surveillance quality.
WHO recommends that all countries maintain a heightened awareness and build
capacity to detect and confirm ZIKV cases; ensure health system preparedness to
respond to a possible increased demand for specialised care (for microcephaly and
neurological syndromes); strengthen antenatal care; and introduce public health
measures to reduce risk of ZIKV spread and infection [9,10].
CONCLUSION
Since the first transmission of ZIKV outside Africa and Asia was documented in an
outbreak in Yap State, FSM in 2007, transmission has been reported in 10 other
Pacific island countries and areas: French Polynesia (2013-14), Cook Islands (2014),
Easter Island (2014), New Caledonia (2014-15), Solomon Islands (2015), Vanuatu
(2015), Fiji (2015), Samoa (2015), and - at the time of writing - the Kingdom of Tonga
(2016) and American Samoa (2016) causing large outbreaks in some. Infection has
being associated with severe clinical complications in French Polynesia. We found
no spatial-temporal correlation between routinely collected AFP data and ZIKV
emergence in previously unaffected Pacific island countries. We suggest the utility of
such a surveillance strategy be further tested in countries that are vulnerable to ZIKV
outbreak and have large populations under the age of 15 years.
http://www.who.int/bulletin/online_first/16-171892.pdf?ua=1