Table 1. Absolute and relative frequency of symptomatic and asymptomatic Plasmodium vivax infections diagnosed by conventional microscopy among members of index, neighbor, and control households (HHs) in four rounds of reactive case detection (RCD) in Acrelândia, Brazil, 2013.
| RCD round | Type of infection | Index HHs | Neighbor HHs | Control HHs | P-valuea | |||
|---|---|---|---|---|---|---|---|---|
| Number of infections | % | Number of infections | % | Number of infections | % | |||
| 1 (Day 0) | Symptomatic | 7 | 4.8% | 5 | 0.7% | 0 | 0.0% | < 0.001 |
| Asymptomatic | 5 | 3.4% | 0 | 0.0% | 1 | 0.2% | < 0.001 | |
| Totalb | 12 | 8.2% | 5 | 0.7% | 1 | 0.2% | < 0.001 | |
| No. tested | 147 | 688 | 634 | |||||
| 2 (Day 30) | Symptomatic | 7 | 4.9% | 8 | 1.2% | 0 | 0.0% | < 0.001 |
| Asymptomatic | 0 | 0.0% | 5 | 0.8% | 0 | 0.0% | 0.05 | |
| Totalc | 7 | 4.9% | 13 | 2.0% | 0 | 0.0% | < 0.001 | |
| No. tested | 143 | 647 | 627 | |||||
| 3 (Day 60) | Symptomatic | 6 | 4.3% | 15 | 2.2% | 0 | 0.0% | < 0.001 |
| Asymptomatic | 4 | 2.8% | 15 | 2.2% | 0 | 0.0% | < 0.001 | |
| Totalc | 10 | 7.1% | 30 | 4.4% | 0 | 0.0% | < 0.001 | |
| No. tested | 141 | 679 | 647 | |||||
| 4 (Day 180) | Symptomatic | 3 | 2.0% | 10 | 1.4% | 2 | 0.3% | 0.038 |
| Asymptomatic | 3 | 2.0% | 12 | 1.7% | 0 | 0.0% | 0.002 | |
| Totalc | 6 | 4.1% | 22 | 3.2% | 2 | 0.3% | < 0.001 | |
| No. tested | 146 | 689 | 678 | |||||
aTwo-tailed P-values for χ2 tests on 3 × 2 contingency tables testing the null hypothesis of similar proportions of positive results across rows.
bPairwise comparisons of positivity rates across row with Fisher exact test (at 5% significance): index HHs > neighbor and control HHs; neighbor HHs = control HHs.
cPairwise comparisons of positivity rates across row with Fisher exact test (at 5% significance): index and neighbor HHs > control HHs; index HHs = neighbor HHs.