TABLE 2. Number of circulating wild polioviruses and circulating vaccine-derived polioviruses detected through environmental surveillance — worldwide, January 1, 2019–June 30, 2021*.
| Country | Jan 1–Dec 31, 2019 | Jan 1–Dec 31, 2020 | Jan 1–Jun 30, 2020 | Jan 1–Jun 30, 2021 | ||||
|---|---|---|---|---|---|---|---|---|
| No. of samples | No. (%) with isolates | No. of samples | No. (%) with isolates | No. of samples | No. (%) with isolates | No. of samples | No. (%) with isolates | |
| Countries with reported WPV1-positive samples (no. and percentage of isolates refer to WPV1) | ||||||||
| Afghanistan | 264 | 57 (22) | 418 | 35 (8) | 172 | 22 (13) | 213 | 1 (1) |
| Iran | 71 | 3 (4) | 43 | 0 (—) | 0 | 0 (—) | 0 | 0 (—) |
| Pakistan | 854 | 379 (44) | 830 | 434 (52) | 414 | 238 (57) | 444 | 59 (13) |
| Countries with reported cVDPV-positive samples (cVDPV type) (no. and percentage of isolates refer to cVDPVs) | ||||||||
| Afghanistan (2) | 264 | 0 (—) | 418 | 175 (42) | 172 | 46 (27) | 213 | 40 (19) |
| Angola (2) | 106 | 17 (16) | 98 | 0 (—) | 47 | 0 (—) | 15 | 0 (—) |
| Benin (2) | 37 | 0 (—) | 70 | 5 (7) | 31 | 0 (—) | 52 | 1 (2) |
| Cameroon (2) | 602 | 4 (1) | 273 | 9 (3) | 134 | 4 (3) | 187 | 0 (—) |
| Central African Republic (2) | 149 | 10 (7) | 97 | 2 (2) | 43 | 2 (5) | 48 | 0 (—) |
| Chad (2) | 198 | 10 (5) | 77 | 3 (4) | 55 | 3 (5) | 26 | 0 (—) |
| China (3) | 0 | 0 (—) | 0 | 0 (—) | 0 | 0 (—) | 1 | 1 (100) |
| Republic of the Congo (2) | 0 | 0 (—) | 12 | 1 (8) | 0 | 0 (—) | 213 | 1 (1) |
| Cote d’Ivoire (2) | 154 | 7 (5) | 130 | 91 (70) | 88 | 62 (70) | 42 | 0 (—) |
| Democratic Republic of the Congo (2) | 294 | 0 (—) | 170 | 1 (1) | 78 | 1 (1) | 145 | 0 (—) |
| Egypt (2) | 703 | 0 (—) | 550 | 1 (0) | 267 | 0 (—) | 313 | 10 (3) |
| Ethiopia (2) | 159 | 3 (2) | 51 | 2 (4) | 33 | 0 (—) | 15 | 0 (—) |
| Gambia (2) | 0 | 0 (—) | 0 | 0 (—) | 0 | 0 (—) | 9 | 2 (22) |
| Ghana (2) | 202 | 17 (8) | 184 | 20 (11) | 100 | 19 (19) | 99 | 0 (—) |
| Guinea (2) | 103 | 0 (—) | 67 | 1 (1) | 38 | 0 (—) | 61 | 0 (—) |
| Iran (2) | 74 | 0 (—) | 43 | 3 (7) | 12 | 0 (—) | 25 | 1 (4) |
| Kenya (2) | 317 | 0 (—) | 193 | 1 (1) | 92 | 0 (—) | 101 | 1 (1) |
| Liberia (2) | 0 | 0 (—) | 34 | 6 (18) | 15 | 0 (—) | 47 | 12 (26) |
| Madagascar (1) | 520 | 0 (—) | 351 | 0 (—) | 232 | 0 (—) | 134 | 12(9) |
| Malaysia (1, 2) | 13 | 12 (92) | 76 | 12 (16) | 50 | 12 (24) | 22 | 0 (—) |
| Mali (2) | 48 | 0 (—) | 44 | 4 (9) | 22 | 2 (9) | 27 | 0 (—) |
| Niger (2) | 293 | 0 (—) | 157 | 7 (4) | 93 | 1 (1) | 73 | 0 (—) |
| Nigeria (2) | 2071 | 60 (3) | 1294 | 5 (0) | 625 | 0 (—) | 868 | 34 (4) |
| Pakistan (2) | 855 | 36 (4) | 830 | 135 (16) | 414 | 35 (8) | 444 | 32 (7) |
| Philippines (1, 2) | 67 | 32 (48) | 80 | 4 (5) | 50 | 4 (8) | 18 | 0 (—) |
| Senegal (2) | 56 | 0 (—) | 27 | 1 (4) | 14 | 0 (—) | 10 | 4 (40) |
| Somalia (2) | 92 | 5 (5) | 88 | 26 (30) | 52 | 18 (35) | 52 | 1 (2) |
| South Sudan (2) | 111 | 0 (—) | 85 | 6 (7) | 57 | 0 (—) | 24 | 0 (—) |
| Sudan (2) | 65 | 0 (—) | 50 | 14 (28) | 20 | 3 (15) | 30 | 0 (—) |
| Tajikistan (2) | 0 | 0 (—) | 0 | 0 (—) | 0 | 0 (—) | 14 | 13 (93) |
| Uganda (2) | 56 | 0 (—) | 58 | 0 (—) | 24 | 0 (—) | 36 | 2 (6) |
Abbreviations: cVDPV = circulating vaccine-derived poliovirus; WPV1 = Wild poliovirus type 1.
* Data are current as of August 3, 2021.