A 35-year-old patient has been suffering from an illness for 3 days. 5 days ago he returned from a trip to Africa. The onset of disease was accompanied by fever up to 40°C, chills, acute headache, myalgia. In the axillary region the lymph node enlarged up to 3x6 cm can be palpated. The lymph node is dense, intensely painful, slightly mobile, without clear margins; the skin over the node is hyperenic and tight. Tachycardia is present. Make the preliminary diagnosis: