United Nations Secretary-General General Antonio Guterres has expressed deep concern over the isolation of southern African countries after several nations imposed travel restrictions against them over the new Omicron coronavirus variant. In a statement on Monday, he commended the Government and science and health community of South Africa for acting early to identify the emergence of a new COVID-19 variant.   But the U.N. Secretary-General recalled that he and others have long warned about low vaccine rates being a breeding ground for variants.   Africa has some of the lowest COVID-19 vaccination rates worldwide due to a lack of access to doses.