The United States and Brazil have witnessed a surge in fresh cases of novel Coronavirus, according to reports on Sunday. Reuters quoted health researchers as saying that the decline in COVID-19 deaths in Manaus, Brazil, meant the city has reached herd immunity. But with a fresh spike in infections, they now believe that the antibodies are not lasting beyond a few months.

"Something that became evident in our study — and that is also being shown by other groups — is that antibodies against SARS-CoV-2 decay quickly, a few months after infection. This is clearly occurring in Manaus," Reuters quoted Leis Buss as saying. Buss is one of the authors of a study by University of Sao Paulo-s Institute of Tropical Medicine.