Shingles can be confused with herpes simplex, dermatitis herpetiformis and impetigo, and skin reactions caused by contact dermatitis, candidiasis, certain drugs and insect bites.

If the rash has appeared, identifying this disease (making a differential diagnosis) requires only a visual examination, since very few diseases produce a rash in a dermatomal pattern (see map). However, herpes simplex virus (HSV) can occasionally produce a rash in such a pattern (zosteriform herpes simplex). The Tzanck smear is helpful for diagnosing acute infection with a herpes virus, but does not distinguish between HSV and VZV.

When the rash is absent (early or late in the disease, or in the case of zoster sine herpete), shingles can be difficult to diagnose. Apart from the rash, most symptoms can occur also in other conditions.

Laboratory tests are available to diagnose shingles. The most popular test detects VZV-specific IgM antibody in blood; this appears only during chickenpox or shingles and not while the virus is dormant. In larger laboratories, lymph collected from a blister is tested by polymerase chain reaction for VZV DNA, or examined with an electron microscope for virus particles. Molecular biology tests based on in vitro nucleic acid amplification (PCR tests) are currently considered the most reliable. Nested PCR test has high sensitivity, but is susceptible to contamination leading to false positive results. The latest real-time PCR tests are rapid, easy to perform, and as sensitive as nested PCR, and have a lower risk of contamination. They also have more sensitivity than viral cultures.

Primary orofacial herpes is readily identified by clinical examination of persons with no previous history of lesions and contact with an individual with known HSV-1 infection. The appearance and distribution of sores in these individuals typically presents as multiple, round, superficial oral ulcers, accompanied by acute gingivitis. Adults with atypical presentation are more difficult to diagnose. Prodromal symptoms that occur before the appearance of herpetic lesions help differentiate HSV symptoms from the similar symptoms of other disorders, such as allergic stomatitis. When lesions do not appear inside the mouth, primary orofacial herpes is sometimes mistaken for impetigo, a bacterial infection. Common mouth ulcers (aphthous ulcer) also resemble intraoral herpes, but do not present a vesicular stage.

Genital herpes can be more difficult to diagnose than oral herpes, since most HSV-2-infected persons have no classical symptoms. Further confusing diagnosis, several other conditions resemble genital herpes, including fungal infection, lichen planus, atopic dermatitis, and urethritis. Laboratory testing is often used to confirm a diagnosis of genital herpes. Laboratory tests include culture of the virus, direct fluorescent antibody (DFA) studies to detect virus, skin biopsy, and polymerase chain reaction to test for presence of viral DNA. Although these procedures produce highly sensitive and specific diagnoses, their high costs and time constraints discourage their regular use in clinical practice.

Until the 1980s serological tests for antibodies to HSV were rarely useful to diagnosis and not routinely used in clinical practice. The older IgM serologic assay could not differentiate between antibodies generated in response to HSV-1 or HSV-2 infection. However, a glycoprotein G-specific (IgG) HSV test introduced in the 1980s is more than 98% specific at discriminating HSV-1 from HSV-2.

It should not be confused with conditions caused by other viruses in the "herpesviridae" family such as herpes zoster, which is caused by varicella zoster virus. The differential diagnosis includes hand, foot and mouth disease due to similar lesions on the skin.

As with almost all sexually transmitted infections, women are more susceptible to acquiring genital HSV-2 than men. On an annual basis, without the use of antivirals or condoms, the transmission risk of HSV-2 from infected male to female is about 8–11%.

This is believed to be due to the increased exposure of mucosal tissue to potential infection sites. Transmission risk from infected female to male is around 4–5% annually. Suppressive antiviral therapy reduces these risks by 50%. Antivirals also help prevent the development of symptomatic HSV in infection scenarios, meaning the infected partner will be seropositive but symptom-free by about 50%. Condom use also reduces the transmission risk significantly. Condom use is much more effective at preventing male-to-female transmission than "vice versa". Previous HSV-1 infection may reduce the risk for acquisition of HSV-2 infection among women by a factor of three, although the one study that states this has a small sample size of 14 transmissions out of 214 couples.

However, asymptomatic carriers of the HSV-2 virus are still contagious. In many infections, the first symptom people will have of their own infections is the horizontal transmission to a sexual partner or the vertical transmission of neonatal herpes to a newborn at term. Since most asymptomatic individuals are unaware of their infection, they are considered at high risk for spreading HSV.

In October 2011, the anti-HIV drug tenofovir, when used topically in a microbicidal vaginal gel, was reported to reduce herpes virus sexual transmission by 51%.

A specific clinical diagnosis of HSV as the cause of dendritic keratitis can usually be made by ophthalmologists and optometrists based on the presence of characteristic clinical features. Diagnostic testing is seldom needed because of its classic clinical features and is not useful in stromal keratitis as there is usually no live virus. Laboratory tests are indicated in complicated cases when the clinical diagnosis is uncertain and in all cases of suspected neonatal herpes infection:

- Corneal smears or impression cytology specimens can be analyzed by culture, antigen detection, or fluorescent antibody testing. Tzanck smear, i.e.Papanicolaou staining of corneal smears, show multinucleated giant cells and intranuclear inclusion bodies, however, the test is low in sensitivity and specificity.

- DNA testing is rapid, sensitive and specific. However, its high cost limits its use to research centers.

- Demonstration of HSV is possible with viral culture.

- Serologic tests may show a rising antibody titer during primary infection but are of no diagnostic assistance during recurrent episodes.

Treatment of herpes of the eye is different based on its presentation: epithelial keratitis is caused by live virus while stromal disease is an immune response and metaherpetic ulcer results from inability of the corneal epithelium to heal:

Testing peoples blood, including those who are pregnant, who do not have symptoms for HSV is not recommended. This is due to concerns of greater harm than benefit such as relationship problems in the setting of a high rate of tests that may be falsely positive.

The likelihood of the infection being spread can be reduced through behaviors such as avoiding touching an active outbreak site, washing hands frequently while the outbreak is occurring, not sharing items that come in contact with the mouth, and not coming into close contact with others (by avoiding kissing, oral sex, or contact sports).

Because the onset of an infection is difficult to predict, lasts a short period of time and heals rapidly, it is difficult to conduct research on cold sores. Though famciclovir improves lesion healing time, it is not effective in preventing lesions; valaciclovir and a mixture of acyclovir and hydrocortisone are similarly useful in treating outbreaks but may also help prevent them.

Acyclovir and valacyclovir by mouth are effective in preventing recurrent herpes labialis if taken prior to the onset of any symptoms or exposure to any triggers. Evidence does not support L-lysine.

Herpes simplex virus is commonly found in humans, yet uncommonly results in systemic manifestations. Suppression of HIV with antiretroviral medications, careful monitoring of immunosuppressive medications are important means of prevention. Antiviral prophylaxis such as daily acyclovir in immunocompromised individuals may be considered.

Key measures to prevent outbreaks of the disease are maintaining hygiene standards and using screening to exclude persons with suspicious infections from engaging in contact sports. A skin check performed before practice or competition takes place can identify individuals who should be evaluated, and if necessary treated by a healthcare professional. In certain situations, i.e. participating in wrestling camps, consider placing participants on valacyclovir 1GM daily for the duration of camp. 10-year study has shown 89.5% reduction in outbreaks and probable prevention of contracting the virus. Medication must be started 5 days before participation to ensure proper concentrations exist.

About 16 percent of Americans between the ages of 14 and 49 are infected with genital herpes, making it one of the most common sexually transmitted diseases. More than 80% of those infected are unaware of their infection. Annually, 776,000 people in the United States get new herpes infections.

Tests for herpes are not routinely included among STD screenings. Performers in the pornography industry are screened for HIV, chlamydia, and gonorrhea with an optional panel of tests for hepatitis B, hepatitis C and syphilis, but not herpes. Testing for herpes is controversial since the results are not always accurate or helpful. Most sex workers and performers will contract herpes at some point in their careers whether they use protection or not.

CMV, VZV as well as HIV infections of the esophagus can have a similar presentation. Tissue culture is the most accurate means of distinguishing between the different viral causes. Caustic esophagitis, pill-induced esophagitis as well as yeast esophagitis can have a similar clinical presentation.

Docosanol, a saturated fatty alcohol, is a safe and effective topical application that has been approved by the United States Food and Drug Administration for herpes labialis in adults with properly functioning immune systems. It is comparable in effectiveness to prescription topical antiviral agents. Due to its mechanism of action, there is little risk of drug resistance. The duration of symptoms can be shortened a bit if an antiviral, anesthetic, zinc oxide or zinc sulfate cream is applied soon after it starts.

Effective antiviral medications include acyclovir and penciclovir, which can speed healing by as much as 10%. Famciclovir or valacyclovir, taken in pill form, can be effective using a single day, high-dose application and is more cost effective and convenient than the traditional treatment of lower doses for 5–7 days.

Herpes outbreaks should be treated with antiviral medications like Acyclovir, Valacyclovir, or Famcyclovir, each of which is available in tablet form.

Oral antiviral medication is often used as a prophylactic to suppress or prevent outbreaks from occurring. The recommended dosage for suppression therapy for recurrent outbreaks is 1,000 mg of valacyclovir once a day or 400 mg Acyclovir taken twice a day. In addition to preventing outbreaks, these medications greatly reduce the chance of infecting someone while the patient is not having an outbreak.

Often, people have regular outbreaks of anywhere from 1 to 10 times per year, but stress (because the virus lies next to the nerve cells), or a weakened immune system due to a temporary or permanent illness can also spark outbreaks. Some people become infected but fail to ever have a single outbreak, although they remain carriers of the virus and can pass the disease on to an uninfected person through asymptomatic shedding (when the virus is active on the skin but rashes or blisters do not appear).

The use of antiviral medications has been shown to be effective in preventing acquisition of the herpes virus. Specific usage of these agents focus on wrestling camps where intense contact between individuals occur on a daily basis over several weeks. They have also been used for large outbreaks during seasonal competition, but further research needs to be performed to verify efficacy.

The majority of cases (85%) occur during birth when the baby comes in contact with infected genital secretions in the birth canal, most common with mothers that have newly been exposed to the virus (mothers that had the virus before pregnancy have a lower risk of transmission), an estimated 5% are infected in utero, and approximately 10% of cases are acquired postnatally. Detection and prevention is difficult because transmission is asymptomatic in 60% - 98% of cases.

Reductions in morbidity and mortality are due to the use of antiviral treatments such as vidarabine and acyclovir. However, morbidity and mortality still remain high due to diagnosis of DIS and CNS herpes coming too late for effective antiviral administration; early diagnosis is difficult in the 20-40% of infected neonates that have no visible lesions. A recent large scale retrospective study found disseminated NHSV patients least likely to get timely treatment, contributing to the high morbidity/mortality in that group.

Harrison's Principles of Internal Medicine, recommends that pregnant women with active genital herpes lesions at the time of labor be delivered by caesarean section. Women whose herpes is not active can be managed with acyclovir. The current practice is to deliver women with primary or first episode non primary infection via caesarean section, and those with recurrent infection vaginally, even in the presence of lesions because of the low risk (1-3%) of vertical transmission associated with recurrent herpes.

The diagnosis of chickenpox is primarily based on the signs and symptoms, with typical early symptoms followed by a characteristic rash. Confirmation of the diagnosis is by examination of the fluid within the vesicles of the rash, or by testing blood for evidence of an acute immunologic response.

Vesicular fluid can be examined with a Tzanck smear, or by testing for direct fluorescent antibody. The fluid can also be "cultured", whereby attempts are made to grow the virus from a fluid sample. Blood tests can be used to identify a response to acute infection (IgM) or previous infection and subsequent immunity (IgG).

Prenatal diagnosis of fetal varicella infection can be performed using ultrasound, though a delay of 5 weeks following primary maternal infection is advised. A PCR (DNA) test of the mother's amniotic fluid can also be performed, though the risk of spontaneous abortion due to the amniocentesis procedure is higher than the risk of the baby's developing fetal varicella syndrome.

Lab Studies:

- No laboratory work is usually necessary.

- Results of cerebrospinal fluid evaluation are abnormal in 61%.

- Pleocytosis is observed in 46%, elevated protein in 26%, and VZV DNA in 22%.

- These findings are not predictive of the clinical course of postherpetic neuralgia.

- Viral culture or immunofluorescence staining may be used to differentiate herpes simplex from herpes zoster in cases that are difficult to distinguish clinically.

- Antibodies to herpes zoster can be measured. A 4-fold increase has been used to support the diagnosis of subclinical herpes zoster (zoster sine herpete). However, a rising titer secondary to viral exposure rather than reactivation cannot be ruled out.

Imaging studies:

- Magnetic resonance imaging lesions attributable to herpes zoster were seen in the brain stem and cervical cord in 56% (9/16) of patients.

- At three months after onset of herpes zoster, 56% (5/9) of patients with an abnormal magnetic resonance image had developed postherpetic neuralgia.

- Of the seven patients who had no herpes-zoster-related lesions on the magnetic resonance image, none had residual pain.

The spread of chickenpox can be prevented by isolating affected individuals. Contagion is by exposure to respiratory droplets, or direct contact with lesions, within a period lasting from three days before the onset of the rash, to four days after the onset of the rash. The chickenpox virus is susceptible to disinfectants, notably chlorine bleach (i.e., sodium hypochlorite). Like all enveloped viruses, it is sensitive to desiccation, heat and detergents.

Diagnosis of FVR is usually by clinical signs, especially corneal ulceration. Definitive diagnosis can be done by direct immunofluorescence or virus isolation. However, many healthy cats are subclinical carriers of feline herpes virus, so a positive test for FHV-1 does not necessarily indicate that signs of an upper respiratory tract infection are due to FVR. Early in the course of the disease, histological analysis of cells from the tonsils, nasal tissue, or nictitating membrane (third eyelid) may show inclusion bodies (a collection of viral particles) within the nucleus of infected cells.

Herpesviral Encephalitis can be treated with high-dose intravenous acyclovir. Without treatment, HSE results in rapid death in approximately 70% of cases; survivors suffer severe neurological damage. When treated, HSE is still fatal in one-third of cases, and causes serious long-term neurological damage in over half of survivors. Twenty percent of treated patients recover with minor damage. Only a small population of survivors (2.5%) regain completely normal brain function. Indeed, many amnesic cases in the scientific literature have etiologies involving HSE. Earlier treatment (within 48 hours of symptom onset) improves the chances of a good recovery. Rarely, treated individuals can have relapse of infection weeks to months later. There is evidence that aberrant inflammation triggered by herpes simplex can result in granulomatous inflammation in the brain, which responds to steroids. While the herpes virus can be spread, encephalitis itself is not infectious. Other viruses can cause similar symptoms of encephalitis, though usually milder (Herpesvirus 6, varicella zoster virus, Epstein-Barr, cytomegalovirus, coxsackievirus, etc.).

Any potential ocular involvement should be assessed by an ophthalmologist as complications such as episcleritis and uveitis may occur.

Anterior uveitis develops in 40–50% of cases with HZO within 2 weeks of onset of the skin rashes. Typical HZO keratitis at least mild iritis, especially if Hutchinson's sign is positive for the presence of vescicles upon the tip of the nose.

Features:

This non-granulomatous iridocyclitis is associated with:

- Small keratic precipitates

- Mild aqueous flare

- Occasionally haemorrhagic hypopion.

HZO uveitis is associated with complications such as iris atrophy and secondary glaucoma are not uncommon. Complicated cataract may develop in the late stages of the disease.

In 1995, the Food and Drug Administration (FDA) approved the Varicella vaccine to prevent chickenpox. Its effect on postherpetic neuralgia is still unknown. The vaccine—made from a weakened form of the varicella-zoster virus—may keep chickenpox from occurring in nonimmune children and adults, or at least lessen the risk of the chickenpox virus lying dormant in the body and reactivating later as shingles. If shingles could be prevented, postherpetic neuralgia could be completely avoided.

In May 2006 the Advisory Committee on Immunization Practices approved a new vaccine by Merck (Zostavax) against shingles. This vaccine is a more potent version of the chickenpox vaccine, and evidence shows that it reduces the incidence of postherpetic neuralgia. The CDC recommends use of this vaccine in all persons over 60 years old.

Diagnosis starts by examining the patient's symptoms. Symptoms can vary. Symptoms can include headache, sensitivity to light, neck stiffness, nausea, and vomiting. In some patients, fever is absent. Neurological examination and MRI can be normal.

Mollaret's meningitis is suspected based on symptoms, and can be confirmed by HSV 1 or HSV 2 on PCR of Cerebrospinal fluid (CSF), although not all cases test positive on PCR. PCR is performed on spinal fluid or blood, however, the viruses do not need to enter the spinal fluid or blood to spread within the body: they can spread by moving through the axons and dendrites of the nerves.

During the first 24 h of the disease the spinal fluid will show predominant polymorphonuclear neutrophils and large cells that have been called endothelial (Mollaret’s) cells.

A study performed on patients who had diffuse symptoms, such as persistent or intermittent headaches, concluded that although PCR is a highly sensitive method for detection, it may not always be sensitive enough for identification of viral DNA in CSF, due to the fact that viral shedding from latent infection may be very low. The concentration of viruses in CSF during subclinical infection might be very low.

Investigations include blood tests (electrolytes, liver and kidney function, inflammatory markers and a complete blood count) and usually X-ray examination of the chest. The most important test in identifying or ruling out meningitis is analysis of the cerebrospinal fluid (fluid that envelops the brain and the spinal cord) through lumbar puncture (LP). However, if the patient is at risk for a cerebral mass lesion or elevated intracranial pressure (recent head injury, a known immune system problem, localizing neurological signs, or evidence on examination of a raised ICP), a lumbar puncture may be contraindicated because of the possibility of fatal brain herniation. In such cases, a CT or MRI scan is generally performed prior to the lumbar puncture to exclude this possibility. Otherwise, the CT or MRI should be performed after the LP, with MRI preferred over CT due to its superiority in demonstrating areas of cerebral edema, ischemia, and meningeal inflammation.

During the lumbar puncture procedure, the opening pressure is measured. A pressure of over 180 mm HO is suggestive of bacterial meningitis.

It is likely that Mollaret meningitis is underrecognized by physicians, and improved recognition may limit unwarranted antibiotic use and shorten or eliminate unnecessary hospital admission.

PCR testing has advanced the state of the art in research, but PCR can be negative in individuals with Mollaret's, even during episodes with severe symptoms. For example, Kojima et al. published a case study for an individual who was hospitalized repeatedly, and who had clinical symptoms including genital herpes lesions. However, the patient was sometimes negative for HSV-2 by PCR, even though his meningitis symptoms were severe. Treatment with acyclovir was successful, indicating that a herpes virus was the cause of his symptoms.