Swine influenza viruses (SIVs) occur worldwide; they usually cause asymptomatic infection but occasionally cause outbreaks of varying intensity (1, 2).
Cystic fibrosis, for example, is caused by a spectrum of different mutations in the CFTR gene, each causing symptoms of varying severity in patients and responding differently to new experimental drugs.
Several poxviruses can infect humans and cause diseases of varying severity.
They may cause dysphonia of varying degrees, especially when associated with other laryngeal lesions such as vocal sulci and cysts.
Other viruses infect humans only as incidental hosts and cause epizootics of varying degrees.
Periodically, sylvatic transmission via Haemagogus or Sabethes vectors have caused outbreaks of varying magnitude and extent in tropical areas of Brazil.
Multiple Sclerosis (MS) is a neurodegenerative disease which runs its course for the remainder of the patient's life frequently causing disability of varying degrees.
The infection can either be asymptomatic or cause illness of varying severity, depending upon the serological status of the recipient and the donor.
The average age at onset of MS is 30 years, and the disease runs its course for the remainder of the patient's life frequently causing disability of varying degrees [ 1].
Some Salmonella serotypes can infect a broad range of domestic animals including poultry, sheep, cattle and pigs and cause symptoms of varying severity ranging from mild gastro-enteritis to death.
