An example of a latent bacterial infection is latent tuberculosis. Rarely is it due to a bacterial infection. Acute cases usually occur as part of a viral upper respiratory tract infection. Mild pneumonia should be differentiated from upper respiratory tract infection (URTI). The hospital diagnosed a severe digestive tract infection. Risk factors include diabetes, a recent upper respiratory tract infection, and pregnancy. Often, symptoms are similar to those of a urinary tract infection. Urinary tract infection (UTI) can occur. Pharyngitis is a type of inflammation caused by an upper respiratory tract infection. Syphilis is difficult to diagnose clinically during early infection. Pharyngitis is a type of upper respiratory tract infection. Giardiasis is the most common pathogenic parasitic infection in humans. Diagnosis of heartworm infection in cats is problematic. Antibiotics may be required in those with an underlying infection. Croup is usually deemed to be due to a viral infection.