West Nile virus is a mosquito-borne flavivirus that is maintained in an enzootic cycle between mosquitoes and birds. Humans and horses are incidental dead-end hosts.
Poliovirus is highly contagious and infected individuals shed virus in the faeces and from oral secretions, thus the mode of transmission is person-to-person, both via the faecal-oral and the oral-oral routes.
Hantaviruses are rodent-borne viruses can be transmitted to humans by contact with faeces/urine from infected rodents or with dust containing infective particles. They may cause severe diseases. Eliminating contact with rodents is the best way to prevent infection.
The transmission of Clostridioides difficile can be patient-to-patient, via contaminated hands of healthcare workers or by environmental contamination.
West Nile virus (WNV) infection is a mosquito-borne zoonosis. The virus is transmitted among birds via the bite of infected mosquitoes and incidentally humans and other mammals may become infected.
Severe acute respiratory syndrome (SARS) is a life-threatening respiratory disease caused by a recently identified coronavirus; the SARS-associated coronavirus (SARS-CoV). This is believed to be an animal virus that recently crossed the species barrier to infect humans.
Poliomyelitis, also known as polio or infantile paralysis, is a vaccine-preventable systemic viral infection affecting the motor neurons of the central nervous system (CNS). Historically, it has been a major cause of mortality, acute paralysis and lifelong disabilities but large scale immunisation programmes have eliminated polio from most areas of the world.