Washington, June 19 : US National Security Adviser Jake Sullivan has tested positive for Covid-19, the latest top official in President Joe Biden's administration to have contracted the virus. Sullivan, 45, is "asymptomatic" and has not been in close contact with Biden, Xinhua news agency quoted Adrienne Watson, a spokesperson for the National Security Council, as saying late Saturday. The NSA's positive result came just days after Anthony Fauci, the US' top infectious disease expert, had tested positive for Covid-19 on a rapid antigen test. An official statement released on Wednesday said that Fauci, director of the National Institute of Allergy and Infectious Diseases (NIAID) and the face of the country's fight against Covid-19, is "fully vaccinated and has been boosted twice" and "is currently experiencing mild symptoms". On June 13, Health and Human Services (HHS) Secretary Xavier Becerra announced he had contracted the virus, while Transportation Secretary Pete Buttigieg was infected on June 6 and Interior Secretary Deb Haaland on June 1. CIA chief William Burns and White House Press Secretary Karine Jean-Pierre also tested positive earlier this year. Covid-19 cases are again increasing across the US. As of Sunday morning, the country's Covid caseload and death toll stood at 87,981,568 and 1,038,289, respectively. The two tallies are the highest in the world, making the US the worst-hit country by the pandemic. /IANS