We also identify selection signals at the SLC22A4 (rs35260072: C; P = 8.49 × 10−20; s = 0.0172) locus, associated with increased itch intensity from mosquito bites (OR 1.049; ref. 52), protection against childhood and adult asthma (OR 0.902 and 0.909; ref. 48) and asthma-related infections (OR 0.913; ref. 48) and we find that the derived variant has been steadily rising in frequency since around 9,000 years ago (Extended Data Fig. 9). The gene discussed is SLC22A4; the disease is infection.