Two additional cases of circulating vaccine-derived poliovirus type 1 (cVDPV1) have been reported from the Lao People’s Democratic Republic (PDR), Laos, according to UN health officials. This brings the number of cVDPV1 cases to seven since October.

Poliovirus  Image/CDC
Poliovirus Image/CDC

The newest cases were reported from Longsane district, Xaisomboun Province. The details of the cases are as follows:

The first new case is a 14-month-old male from Longsane district, Xaisomboun Province. He developed fever on 16 November, progressing to hyporeflexia and asymmetric paralysis in both legs by 18 November. Local health authorities reported the AFP case on 19 November. Vaccination history indicated that the child had received three doses of oral polio vaccine (OPV). On 1 and 3 December, samples of the patient were collected and shipped to the National Institute of Infectious Diseases (NIID) in Japan for testing. On 21 December, the samples tested negative for any polioviruses. However, a sample taken from his asymptomatic sister tested positive for VDPV1. The 14-month old AFP case was classified by the National Coordination Committee as VDPV1 case based on the epidemiological link with the positive contact and also as one additional AFP case from the same district tested positive for VDPV1 indicating the plausibility of VDPV1 circulation in the area.

The second new case is a 40-year-old male from Longsane district, Xaisomboun Province. The patient presented with symptoms on 18 December with hyporeflexia and symmetric paralysis in both legs, but no pulmonary involvement. No fever was reported. The patient had no recent history of any nervous system disease, recent trauma, or animal or insect bites. He had not received any OPV. The Vientiane Provincial Hospital informed the Provincial Health Department of an AFP case on 21 December and a case investigation was conducted on the same day, including stool specimen collection. On 9 January, NIID reported that this patient tested positive for VDPV1.

Since the detection of the first confirmed cVDPV1 in Lao PDR, outbreak response activities have been conducted nationwide, including the national round in December and the affected provinces (Bolikhamxay and Xaisomboun) and a neighbouring province (Xiengkhuang). The national Emergency Operations Centre has been activated to coordinate response efforts and a polio outbreak response plan was drafted. Enhanced surveillance is occurring throughout the country, including daily zero-reporting of AFP cases. Active case finding is ongoing in high risk districts, including retrospective review of hospital and health centre records.

Six rounds with trivalent OPV vaccine have been planned from October 2015 to March 2016 (4 sub-national and 2 national) with approximately 10 million doses to be administered to children younger than 15 years. Three rounds of supplementary immunization activity (SIA) with OPV vaccine were completed in October, November and the first nationwide round in December. The fourth round is planned for 25 January to 7 February in all 15 provinces which were targeted in December 2015 including 19 high risk districts targeting all ages. This age range was determined by the age distribution of the cases and their cVDPV1 positive contacts. Independent monitors have been recruited to assess the quality of these campaigns.