COVID-19 and other serious viral infections can activate dormant cancer in the lungs and increase the risk of it returning, even years after the original infection[1][2]. Researchers found that people who tested positive for COVID-19 had an 85 percent higher risk of dying from cancer and a 4.5 times higher risk of death compared to those who tested negative[1]. Women with breast cancer who survived COVID-19 had a 44 percent higher risk of developing cancer metastases to the lungs[1]. The mechanism of this process consists in the fact that COVID-19 causes the production of an inflammatory substance called interleukin-6 in the lungs, which awakens sleeping cancer cells and triggers their multiplication[1][2]. Scientists confirmed this with experiments on mice - when the mice could not produce interleukin-6, the COVID-19 virus was no longer able to wake up sleeping cancer cells[1]. The risk of death from cancer was highest in the first months after infection and gradually decreased[1]. A similar process also takes place with the flu[1].