National Polio Surveillance, Yemen Ministry of Public Health and Population, Sana'a, Yemen.
Field Epidemiology Training Program, Yemen Ministry of Public Health and Population, Sana'a, Yemen.
BMC Infect Dis. 2022 Apr 29;22(1):414. doi: 10.1186/s12879-022-07397-0.
Yemen has faced one of the worst humanitarian crises in the world since the start of the war in 2015. In 2020; 30 Vaccine Derived Polio Virus type 1 (VDPV1) isolates were detected in Saadah governorate. The aims are to characterize the outbreak and address the gaps predisposing the emergence and circulation of VDPV1 in Saadah governorate, Yemen.
A retrospective descriptive study of confirmed cases of VDPV1 between January and December 2020 was performed. Surveillance staff collected data from patient cases, contacts, as well as stool specimens that shipped to WHO accredited polio labs. Data of population immunity was also reviewed. The difference in days between the date of sample collection, shipment, and receiving lab result was used to calculate the average of delayed days for lab confirmation.
From January to December 2020, a total of 114 cases of acute flaccid paralysis (AFP) were reported from 87% (13/15) districts, and cVDPV1 was confirmed among 26% (30) AFP cases. 75% (21) were < 5 years, 73% (20) had zero doses of Oral Polio Vaccine (OPV). The first confirmed case (3%) was from Saadah city, with paralysis onset at the end of January 2020 followed by 5 cases (17%) in March from another four districts, 8 cases (27%) in April, and 13 (43%) up to December 2020 were from the same five districts in addition to 3 (10%) form three new districts. The lab confirmation was received after an average of 126 days (71-196) from sample collection. The isolates differ from the Sabin 1 type by 17- 30 VP1 nucleotides (nt) and were linked to VDPV1 with 13 (nt) divergence that isolated in July 2020 from stool specimens collected before one year from contacts of an inadequate AFP case reported from Sahar district.
The new emerging VDPV1 was retrospectively confirmed after one year of sample collection from Sahar district. Delayed lab confirmation, as well as the response and low immunization profile of children against polio, were the main predisposing factors for cVDPV1 outbreak. This outbreak highlights the need to maintain regular biweekly shipments to referral polio labs in the short-term, and the exploration of other options in the longer-term to enable the Yemen National Lab to fully process national samples itself.
自 2015 年战争爆发以来，也门一直面临着世界上最严重的人道主义危机之一。2020 年，在萨达省发现了 30 株疫苗衍生脊髓灰质炎病毒 1 型（VDPV1）。本研究旨在对此次暴发进行特征描述，并确定导致 VDPV1 在也门萨达省出现和传播的风险因素。
对 2020 年 1 月至 12 月间确诊的 VDPV1 病例进行回顾性描述性研究。监测人员从患者病例、接触者以及运往世界卫生组织认可的脊灰实验室的粪便标本中收集数据。还审查了人口免疫数据。利用样本采集日期、发货日期和实验室收到结果日期之间的天数差异，计算实验室确认的平均延迟天数。
2020 年 1 月至 12 月期间，87%（13/15）的 8 个区报告了 114 例急性弛缓性麻痹（AFP）病例，其中 26%（30 例）的 AFP 病例确认为 cVDPV1。75%（21 例）的患者年龄<5 岁，73%（20 例）未接种过口服脊髓灰质炎疫苗（OPV）。首例确诊病例（3%）来自萨达市，发病时间为 2020 年 1 月底，随后 3 月来自另外 4 个区的 5 例（17%）、4 月 8 例（27%）、2020 年 12 月前的 13 例（43%），均来自同一 5 个区，另外还有 3 例（10%）来自 3 个新的区。从样本采集到实验室确认的平均时间为 126 天（71-196 天）。这些分离株与 Sabin 1 型的差异为 17-30 个 VP1 核苷酸（nt），与 2020 年 7 月从 Sahar 区一名 AFP 病例接触者粪便标本中分离的 13 个（nt）差异的 VDPV1 有关，该病例发病前一年曾报告过一次。
在从 Sahar 区采集样本一年后，对新出现的 VDPV1 进行了回顾性确认。实验室确认的延迟，以及儿童对脊灰疫苗的反应和低免疫状况，是导致 cVDPV1 暴发的主要危险因素。此次暴发突显了在短期内需要定期每两周向脊灰参考实验室运送样本的必要性，并需要在长期内探索其他选择，以使也门国家实验室能够自行全面处理本国样本。
