The incubation period of EHF generally lasts for 2–21 days, commonly 5–12 days. The cases of EBOV infection can be asymptomatic or have mild symptoms. Non-critical cases gradually recover 2 weeks after the onset. The typical cases with EHF have an acute onset, with clinical manifestations of high fever, aversion to cold, headaches, muscle and joint pain (commonly major joints and lumbosacral region), vomiting, conjunctival congestion, and relatively slow pulse. Gastrointestinal symptoms occur 2–3 days after the onset, characterized by diarrhea (firstly watery and following dark) along with vomiting and angina. The cases develop into the climax stage 4–5 days after the onset, characterized by conscious change such as delirium and drowsiness. In serious cases, hemoptysis and bleeding in the nose, mouth, subconjunctiva, gastrointestinal tract, vagina, and skin as well as hematuria can be found several days after the onset. The bleeding peaks at day 10 after the onset. Due to necrosis and decomposition of the organs, patients continually vomit the necrotic tissue via their mouth. Above 50 % of the patients have serious bleeding, and death occurs due to bleeding as well as hepatic and renal failure. The prominent manifestations include hypotension, shock, and facial edema, DIC, as well as electrolytes and acid-base balance disturbances. After infection of EBOV by pregnant women, uterine bleeding and miscarrying occur. In the death cases, 90 % have its occurrence within 12 days after the onset. The early symptoms after the onset of EHF are deceptive and tend to be misdiagnosed as common cold, flu, measles, cholera, typhoid fever, malaria, and HIV/AIDS that are common in Africa. Thus, its early diagnosis is difficult to be defined. However, its definitive diagnosis after various bleedings is too late to save the life.

Complications in the acute stage include myocarditis and bacterial pneumonia. In not serious cases, patients gradually recover in 2 weeks after the onset. Most patients have asymmetrical joint pain that may be migratory that mainly involves major joints. Some patients show delayed symptoms, including myalgia, fatigue, suppurative parotitis, hearing loss or tinnitus, conjunctivitis, unilateral blindness, and uveitis. Due to the long-term survival of the virus in the seminal fluid, delayed diseases such as testitis and testicular atrophy can be induced. At day 5–7 during the course of the disease, measles-like macula may occur that is common on the shoulders, palms, and soles. The macula is absent with desquamation after several days. Some patients may have long-term residual skin changes.

Laboratory tests for the diagnosis of EHF mainly include etiological examination, serologic test, electron microscopy, and virus isolation. The serologic test and virus isolation are more commonly applied in clinical practice.