Estimated global incidence of Japanese encephalitis: a systematic review
Grant L Campbell, Susan L Hills, Marc Fischer, Julie A Jacobson, Charles H Hoke, Joachim M Hombach, Anthony A Marfin, Tom Solomon, Theodore F Tsai, Vivien D Tsu & Amy S Ginsburg
Volume 89, Number 10, October 2011, 766-774E
Table 2. Summary of the 12 primary references used to estimate the incidence of Japanese encephalitis (JE) in Asia, by incidence group
| IG | Country | Reference | Study type | Laboratory-confirmed |
Study period | Study area | Study age group | Estimated study population | Estimated annual incidencea | Relative quality of study data | |
|---|---|---|---|---|---|---|---|---|---|---|---|
| No. | % | ||||||||||
| A | Japan | Arai et al. (2008) |
Routine (passive) national surveillance | 53 | 100 | 1992–2004 (13 years) | Entire country | All | 126.4 million (approx. mid-interval population) | 0.003 | Medium-quality data from national surveillance system based on physician reports of laboratory-confirmed cases; caveats include that laboratory methods used have evolved over time. |
| Hashimoto et al. (2007) |
Routine (passive) national surveillance | 33 | 100 | 2000–2005 (6 years) | Entire country | All | 126.55 million | 0.004 | Medium-quality data from national surveillance, based on laboratory confirmation of physician-reported, clinically suspected cases. | ||
| C1 | China | Yin et al. (2010) |
Multiple hospital-based surveillance | 121 | 100 | Apr. 2007 to Sept. 2008 (17 months) or Sept. 2006 to Sept. 2008 (25 months), depending on prefecture | Guigang prefecture, Guangxi province; Yichang prefecture, Hubei province; Jinan prefecture, Shandong province | All | 14.13 million | 0.6b | Medium-quality data from 6 carefully selected sentinel hospitals in each prefecture; caveats include that not all hospitals in each prefecture were included. |
| Xufang et al. (2010) |
Multiple hospital-based surveillance | 1609 | 75 | 2006 (1 year)c | Guizhou province | All | 37.6 million | 4.3 | Medium-quality data; all hospitals in the province were included in surveillance, but samples were unavailable for testing in 25% (455/1837) of clinically suspected cases, so incidence estimate was adjusted upward, based on seropositivity rate among those tested. | ||
| C2 | China | Yin et al. (2010) |
Multiple hospital-based surveillance | 18 | 100 | Apr. 2007 to Sept. 2008 (17 months) | Shijiazhuang prefecture, Hebei province | All | 5.06 million | 0.01d | See above. |
| D | Cambodia | Touch et al. (2009) |
Multiple hospital-based surveillance | 583e | 19 | 2007 (1 year) | Entire country | 0–14 years | 5.25 million | 11.1 | Medium-quality data from 6 carefully selected sentinel hospitals distributed throughout the country. |
| Indonesia | Kari et al. (2006) |
Multiple hospital- and clinic-based enhanced (active) surveillance | 90 | 100 | July 2001 to Dec. 2003 (2.5 years) | Bali province | 0–11 years | 599 120 | 6.0 | High-quality data; all health care facilities in the province providing care for the study population were included in active surveillance system. | |
| Thailand | Hoke et al. (1988) |
Vaccine trial; enhanced (active) local public health surveillance | 11 | 100 | 1985–1986 (2 years) | Kampangphet province | 1–14 years | 21 516 | 25.6 | High-quality data; all health care facilities in the province providing care for the study population were included in active surveillance system. | |
| F | Nepal | Partridge et al. (2007) |
Multiple hospital-based surveillance | 225 | (100) | 2006 (1 year) | Terai & Inner Terai districts (n = 24) | All | 12.46 milliong | 1.8 | Medium-quality data from national surveillance system, based on laboratory confirmation of clinically suspected cases using an incomplete network of 93 hospitals and clinics; caveats include that specimens for laboratory testing were unavailable in 16% of clinically suspected cases, with no adjustment for this potential source of underdiagnosis. |
| Wierzba et al. (2008) |
Multiple hospital-based surveillance | 951 | 100 | May 2004 to Apr. 2006 (2 years) | Terai & Inner Terai districts (n = 24) | All | 12.46 milliong | 3.8 | Medium-quality data from national surveillance system, based on laboratory confirmation of clinically suspected cases using an incomplete network of 64 hospitals; caveats include that specimens for laboratory testing were unavailable in 31% of clinically suspected cases, with no adjustment for this potential source of underdiagnosis. | ||
| G | Bangladesh | Paul et al. (in press) |
Multiple hospital-based surveillance | 472d | 8 | Oct. 2007 to Dec. 2008 (15 months) | Bagerhat, Chittagong, Cox's Bazar, Jessore, Jhenaidah, Khulna, Naogaon, Narail, Nawabganj, Rajshahi, & Satkhira districts | All | 27.5 million | 1.4d | Relatively lower quality data because incidence was not directly measured, but rather extrapolated retrospectively from hospitalized, laboratory-confirmed cases to non-hospitalized, clinically suspected but laboratory-untested patients. |
| Nepal | Partridge et al. (2007) |
Multiple hospital-based surveillance | 67 | 100 | 2006 (1 year) | Mountain and hill (non-Terai) districts (n = 51) | All | 10.69 milliong | 0.6 | See above. | |
| Wierzba et al. (2008) |
Multiple hospital-based surveillance | 84 | 100 | May 2004 to Apr. 2006 (2 years) | Mountain and hill (non-Terai) districts (n = 51) | All | 10.69 milliong | 0.4 | See above. | ||
| Bhattachan et al. (2009) |
Multiple hospital-based surveillance | 90 | 100 | 2007 (1 year) | Mountain and hill (non-Terai) districts (n = 51) | All | 10.69 milliong | 0.8 | Medium-quality data from national surveillance system, based on laboratory confirmation of clinically suspected cases using an incomplete network of hospitals; specimens for laboratory testing were available in 96% of clinically suspected cases. | ||
| H | Malaysia | Wong et al. (2008) |
Single hospital-based surveillance | 49 | 100 | July 2001–2006 (post-vaccine programme) (5.5 years) | Sibu Hospital, Sarawak state | All | 600 000 (in catchment area) | 1.5 | Medium-quality data from a single, central, large, sentinel hospital; caveats include that incidence estimates were apparently based on the assumption that 100% of JE cases in this hospital’s catchment area would present to this hospital, and that none from outside the catchment area would do so. |
IG. incidence group.
a Per 100 000.
b Weighted average of results from all three prefectures (using raw incidence data, as data used in their adjustment of incidence rates were not provided).
c April to November, but because this timeframe brackets the JE transmission season in the region, 1 year was used.
d Using raw incidence data, as data used in their adjustment of incidence rates were not provided.
e 100% of study cases were laboratory-confirmed; the study's authors then extrapolated their results to a larger geographic area, proportionate to the total number of acute encephalitis syndrome cases reported.
f These historical, pre-vaccination-era data from Thailand were used, in part, to estimate incidence in Incidence Group D, but present-day Thailand was included in Incidence Group H.
g 2001 census data.