A broad variety of viral agents may be the cause of conjunctivitis. While some species (e.g. adenovirus) directly infect the conjunctiva, other species cause
conjunctivitis in association with a systemic viral infection. We will briefly discuss the various etiologies.
Adenoviruses are the most common cause of viral conjunctivitis. They are medium-sized, nonenveloped, icosadhedral viruses composed of a nucleocapsid and double
stranded DNA genome. They are responsible for many infections in addition to conjunctivitis including upper and lower respiratory tract disease, gastroenteritis,
and hemorrhagic cystitis.3 Generally they are divided into 6 species (A-F) making up a total of 51 serotypes. Only a few of the serotypes are
responsible for most cases of conjunctivitis, notably serotypes 8, 19 and 37.4
Adenoviruses are extremely contagious and may be spread by direct or indirect contact with ocular or upper respiratory tract secretions.5 Public
spaces, in particularly eye clinics, are a major source of spread and even pools and hot tubs have been shown to be sources for virus transmission.6
It usually has an incubation between 2 days to 2 weeks following exposure, during which it is probably not contagious (studies suggest viral particles are not
detectable in the conjunctiva prior to symptom onset).5 Following symptom onset, the condition is often contagious for 2 weeks or longer.
Most cases of adenoviral conjunctivitis are benign. Generally, three patterns of disease are seen with adenoviral conjunctivitis, although differentiating
patterns in a clinical setting is often irrelevant.These include:
Epidemic keratoconjunctivitis: epidemic keratoconjunctivitis (EKC) is especially contagious and most frequently caused by serotypes 8, 19 and 37
(other possible serotypes being 2-5, 7, 10, 11, 21, 22, 29, and 342). It typically involves the cornea to some degree along with conjunctivitis,
and often occurs in epidemics, especially in crowded living conditions (e.g. schools, military bases, ophthalmic practices3).
Pharyngoconjunctival fever: pharyngoconjunctival fever is a common pattern of adenoviral conjunctivitis seen that is characterized by a mild
follicular reaction on the inferior tarsal conjunctiva in association with a systemic viral syndrome. It most commonly affects children and is
caused by serotypes 3 and 7.2
Nonspecific follicular conjunctivitis: may be caused by multiple serotypes including 1-11, 15-17, 19, 20, and 22.2
Acute hemorrhagic conjunctivitis
Acute hemorrhagic conjunctivitis describes a severe but often self-limited conjunctivitis of viral origin that often occurs in epidemics in developing countries or
communities of low socioeconomic status. It is caused primarily by enterovirus type 70 or coxsackie virus type A24 (both species of picornavirus) and is also very
contagious. Children and young adults are often affected. The disease is characterized by a conjunctivitis that is more severe than adenoviral conjunctivitis and
often accompanied by subconjunctival hemorrhages. It often has no long-term sequelae, but the viruses can cause neurological and systemic disease.7 No
treatment is often indicated, however studies have shown interferon to reduce interhousehold spread.8
Herpes simplex virus
A full discussion of ocular herpes simplex is beyond the scope of this module. However, it should be noted that both herpes simplex virus (HSV) 1 and less commonly
HSV 2 can cause conjunctivitis during primary or recurrent infection. Primary ocular HSV infection is common in infants and children and usually associated with a
Herpes zoster virus
Similarly, a full discussion of herpes zoster and the eye is beyond the scope of this module. However, herpes zoster infection may cause conjunctivitis during both
primary (i.e. chicken pox) and reactivation (i.e. zoster) infection, and may occur with or without skin lesions. Primary infection is contracted through direct contact
with skin lesions or respiratory secretions (may be airborne), and in addition to the characteristic rash (vesicular rash on body and head that becomes itchy with raw
pockmarks) may be associated with a mild conjunctivitis or episcleritis.9 There may also be pox (focal areas of necrosis) on the corneal stroma or conjunctiva.
Recurrent zoster (or simplex) may occur following stress, fever, trauma, hormonal changes, reduced cell-mediated immunity or exposure to sunlight.10 11 Herpes
zoster ophthalmicus may in addition to corneal findings be associated with conjunctival hyperaemia, petechial hemorrhages, a papillary or follicular conjunctivitis, and
rarely a pseudomembrane.12 One study estimated that up to 25% of zoster cases occur along the ophthalmic branch of V1.11
Molluscum contagiosum is a viral infection caused by a poxvirus that produces benign, self-limiting papular eruptions of the skin and mucous membrane.13 It is most commonly seen in
children and immunocompromised individuals (e.g. AIDS, systemic steroids, etc.). Ocular lesions are not uncommon, and typically involve the eyelid. Such lesions can produce a follicular
conjunctivitis or keratoconjunctivitis, thought to be secondary to toxicity or hypersensitivity to viral proteins shed from the lesion onto the tear film.13 Associated findings may
include a punctuate keratopathy or epithelial/subepithelial infiltrates.14 15 Conjunctivitis can often be chronic in such cases. Rarely, molluscum may produce conjunctival lesions.
Molluscum contagiosum often runs a benign and self-limiting course. In cases associated with chronic anterior segment involvement such as conjunctivitis or keratoconjunctivitis,
removal of the cutaneous lesion should be considered as it usually improves the condition.15 Options include resection, curettage, cryotherapy, or cautery. The lesions
often recur. In patients with HIV infection, treatment with highly active anti-retroviral therapy (HAART) often results in complete regression of the lesions as well.
Human immunodeficiency virus
Human immunodeficiency virus (HIV), the agent responsible for AIDS, often has ocular manifestations which can
occasionally involve the anterior segment. Firstly, conjunctivitis (e.g. viral) is often more severe and prolonged
in patients with HIV due to reduced immune clearance of the virus. Also, many patients with HIV will have
occasional transient nonspecific conjunctivitis with irritation, hyperaemia and tearing. Such cases often
do not come to medical attention and if so, do not require treatment. Finally, patients with HIV and
especially those with low CD4 counts can have conjunctival or cornea infection from microsporidia, an
opportunistic fungal/protozoan species. Such infections often resolve with proper antimicrobial treatment.
It should also be noted that many patients with HIV display abnormal conjunctival vasculature secondary to
“conjunctival microvasculopathy” that may make the eye appear red.
Multiple other systemic viral infections can have an associated mild conjunctivitis.Examples include:
Measles: measles (aka rubeola) is a respiratory tract infection caused by a paramyxovirus.
The classic symptoms are cough, coryza (runny nose) and conjunctivitis, with other symptoms/signs including
fever, Koplik’s spots (inside the mouth) and a maculopapular, erythematous rash starting on the head
and becoming generalized. In its early stages, it may cause photophobia, conjunctivitis, and iritis. Because
of the widespread vaccination programs with the MMR vaccine, the disease is much less common but small cluster
still occur. Treatment is supportive with monitoring for complications.7
Mumps: mumps, another infection significantly decreased in incidence since MMR vaccination,
is an infection caused by the mumps virus that causes inflammation of salivary (often parotid) and other glands.
It often begins with prodromal symptoms of myalgias, anorexia, malaise, headache and fever that may occur with
dacroadenitis before parotitis becomes evident. Commonly an acute conjunctivitis with mucoid discharge or
episcleritis is present. Patients may have photophobia and tearing. Treatment is supportive.
Rubella: rubella (“German measles”) is an infection caused by the rubella virus
that is also rarely seen in developed countries since MMR vaccination. It is characterized by an often mild
disease with an erythematous rash starting on the head and spreading inferiorly. It often causes mild follicular
conjunctivitis appearing 2-3 days before the rash and lasting a few days. Recognition of rubella is especially
important in women of child-bearing age as infections during pregnancy can cause severe neonatal problems
(i.e. congenital rubella syndrome).
Influenza: influenza virus is occasionally associated with a mild conjunctivitis.17