Kernig's sign is observed in Aseptic meningitis. Kernig's sign is  positive when the thigh is bent at the hip and knee at 90 degree angles, and subsequent extension in the knee is painful. Aseptic meningitis, or sterile meningitis, is a condition in which the layers lining the brain, meninges, become inflamed caused by Herpes simplex virus 2.

Progressive Multifocal Leukoencephalopathy (PML) is a disease of the white matter of the brain, caused by JC (John Cunningham) virus infection that targets cells that make myelin - the material that insulates nerve cells (neurons).

Herpes simplex virus type 2 is associated with Aseptic meningitis. It is an inflammation of the meninges (the membranes covering the brain and spinal cord) caused by viral infection.

Ebola virus was the cause of the 2013–2015 epidemic in West Africa, which resulted in at least 28,638 suspected cases and 11,315 confirmed deaths. It causes fatal hemorrhagic fever in humans and other mammals.

Hepatitis A is transmitted by faecal-oral route and hence, causes acute hepatitis.

Bunyavirus, Flavivirus and Togavirus are exclusively transmitted by arthropods.

Hantaan river virus is the causative agent of Korean hemorrhagic fever in humans. Initial symptoms begin suddenly and include intense headaches, back and abdominal pain, fever, chills, nausea and blurred vision. Individuals may have flushing of the face, inflammation or redness of the eyes or a rash. Later symptoms can include low blood pressure, acute shock, vascular leakage and acute kidney failure, which can cause severe fluid overload.

HIV virus does not belong to risk group IV human pathogens. Risk Group 4 (RG4) agents are likely to cause serious or lethal human disease for which preventive or therapeutic interventions are not usually available. HIV is a group II virus because for it, preventative or therapeutic interventions are often available.

Human parainfluenza virus type 3 (HPIV-3) is associated with bronchiolitis and pneumonia.

Karl Landsteiner and Erwin Popper discovered poliovirus in 1908 by proving that it was not a bacterium that caused paralysis, but a much smaller entity - a virus.

Yellow fever is caused by yellow fever virus, which is spread by the bite of female mosquito. It spreads primarily by Aedes aegypti mosquito.

Coronavirus is the only enveloped causative agent of gastroenteritis.

Reye's syndrome is a rapidly progressive encephalopathy, which usually begins shortly after recovery from an acute infection of influenza virus.

Parvovirus B19 causes a childhood rash disease called fifth disease or erythema infectiosum, or slapped cheek syndrome. Symptoms are bright red rash of the cheeks, fever, diarrhea, nausea, exacerbation of rash by the sunlight, heat and stress.

The risk of Hodgkin's lymphoma increases in the presence of Epstein-Barr virus,  but the precise contribution of Epstein–Barr virus remains largely unknown. Epstein-Barr virus causes infectious mononucleosis. Both the diseases affect lymph nodes.

This is the correct match. Colt virus causes Colorado tick fever, Orbivirus causes blue tongue disease in sheep, cattle, goats and wild ungulates, Banna virus causes encephalitis and Rota virus is associated with diarrhoea in children.