Presentation and diagnosis of an initial episode of oral mucocutaneous herpes

In neonates, infection with herpes simplex virus (HSV) can present as isolated skin or mucous membrane lesions, encephalitis, pneumonitis, or a disseminated infection. Management is complex and specialist advice is required; for more information on management of herpes simplex infection in neonates, see Neonatal herpes simplex infection in the Antibiotic guidelines.

In children and adults, the initial episode of oral mucocutaneous herpes is typically more severe than subsequent recurrent episodes—for presentation and treatment of recurrent oral mucocutaneous herpes, see hereThe Royal Children's Hospital (RCH), 2018.

In children, initial oral infection of HSV usually presents as herpetic gingivostomatitis (inflammation of the gums and lips); however, some children may not show any symptoms of initial infectionThe Royal Children's Hospital (RCH), 2018. In addition to painful intraoral lesions, signs and symptoms of herpetic gingivostomatitis include fever, irritability The Royal Children's Hospital (RCH), 2018, lethargy and cervical lymphadenopathy. Children may find eating and drinking difficult, leading to dehydration; refer children with signs of severe dehydration to the hospital emergency department. Also refer to hospital emergency department if a child with herpes simplex gingivostomatitis shows symptoms of encephalitis (a rare but serious complication)The Royal Children's Hospital (RCH), 2018.

In adults, initial oral infection of HSV often presents as severe pharyngitis. Herpetic gingivostomatitis is rare in adults, but can be severe. Adults can present with dehydration caused by severe odynophagia (painful swallowing).

Intraoral HSV lesions begin as blisters and ulcerate rapidly. Blisters and ulcers usually take 10 to 14 days to healThe Royal Children's Hospital (RCH), 2018.

When assessing a patient with a suspected initial episode of intraoral HSV lesions, consider other causes such as:

• other viruses (eg varicella zoster virus, coxsackie virus, cytomegalovirus)—HSV is the most common viral cause of mouth ulcers, but other viruses can also be a cause
• necrotising gingivitis—necrotising gingivitis is rare in children and is confined to the gingival tissues, while herpetic gingivostomatitis lesions are widespread and affect all soft tissues in the mouth.

Diagnosis of oral mucocutaneous herpes is usually clinical, but if confirmation is required (eg in an immunocompromised patient or contact), take a swab for polymerase chain reaction (PCR) or rapid immunofluorescence. Serology is rarely helpfulThe Royal Children's Hospital (RCH), 2020.

Oral mucocutaneous herpes infection may be the initial presentation of undiagnosed HIV infection—in severe presentations, consider HIV infection (see here).