Mpox vs. Chickenpox: What Are the Differences?

Mpox (formerly known as monkeypox) and chickenpox are two contagious viral diseases. They both have "pox" in their names because they cause pockmark skin lesions. But mpox is caused by a virus similar to smallpox, while a type of herpesvirus causes chickenpox.

While they share similar symptoms (like fever, fatigue, headaches, and a blistering rash), mpox and chickenpox differ by how the viruses are spread, the locations of the rashes, the populations they most commonly affect, and how each is treated.

This article describes the differences between mpox and chickenpox in symptoms, causes, diagnosis, and treatment.

If you have a rash, be sure to see a healthcare provider for a diagnosis so that you can receive the appropriate treatment.

Symptoms

No less than three dozen viral diseases have "pox" in their names, the most familiar of which are chickenpox, smallpox, and mpox. All of these diseases share an itchy, blistering rash.

Mpox and chickenpox progress in a similar way. Flu-like symptoms, such as headache, fever, and fatigue, precede the outbreak of the rash. These are referred to as prodromal symptoms.

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Within days, a rash will appear as small dots or pimples that quickly enlarge and fill with a clear or yellowish fluid. This blistering rash, typically itchy and sometimes painful, erupts, scabs over, and begins to heal.

Despite these similarities, there are a number of key differences between mpox and chickenpox, including:

• Asymptomatic infection: Studies reveal that around 1 in 14 people with mpox are asymptomatic, meaning that they have no symptoms but can still transmit the virus to others. Chickenpox is rarely asymptomatic but can sometimes be so mild as to go unrecognized.
• Prodromal symptoms: Lymphadenopathy (swollen lymph nodes) is characteristic of mpox but not chickenpox. Also, many children with chickenpox have no prodromal symptoms.
• Distribution of rashes: Mpox may only cause a single lesion or a few lesions. But at other times it can cause thousands of lesions, most often on the face and extremities rather than the trunk. Chickenpox rashes tend to be more widespread, affecting the face, scalp, torso, upper arms, and legs.
• Location of rashes: With mpox, the rash can develop on the palms of the hands and soles of the feet, around the genitals and anus, and on the eyes (where they can cause corneal scarring). These are uncommon locations for chickenpox.
• Duration of symptoms: Mpox takes longer to resolve than chickenpox. Mpox rashes develop three to 17 days after exposure, with symptoms lasting two to three weeks. With chickenpox, the rash will appear within 10 to 21 days, with symptoms lasting four to seven days.

While mpox and chickenpox can be distressing and cause extreme discomfort, they are rarely life-threatening.

Causes

The main difference between mpox and chickenpox is the virus that causes them. Mpox is caused by the mpox virus (MPV), one of several viruses, along with smallpox, that are classified as Orthopoxviruses.

By contrast, chickenpox is caused by a herpesvirus known as the varicella-zoster virus (VZV), not by a true poxvirus. Chickenpox is also a much milder disease than smallpox was before it was eradicated (done away with completely).

VZV has many of the same characteristics as herpes simplex virus type 1 (HSV-1), commonly linked to cold sores, and herpes simplex virus type 2 (HSV-2), commonly linked to genital herpes. Chief among these is the risk of recurrence.

Mpox vs. Chickenpox Transmission

Because the two viruses are completely different, the ways in which mpox and chickenpox are transmitted (passed) also differ, as follows:

• Mpox transmission: The mpox virus is transmitted by direct contact with rashes and scabs as well as contact with saliva and respiratory secretions (saliva and mucus) of a person with the virus. Mpox can also be transmitted through oral, vaginal, or anal sex or by touching the genitals or anus of someone with mpox.
• Chickenpox transmission: VZV is spread by contact with the rash or scabs, but it can also be passed by inhaling aerosolized fluids from a chickenpox sore that contains the virus. It may also be possible for VZV to be passed through respiratory (airborne) droplets.

Of the two, chickenpox is far more contagious as the virus can be transmitted through the air. If you have not been vaccinated against chickenpox or haven't had the illness and spend time around someone with chickenpox, the chances are high that you will contract the virus.

Affected Populations

Mpox can affect people of any age, although adults 31 to 45 accounted for most infections during the 2022 outbreak in the United States. Intimate exposure, such as during sexual contact, appeared to be the primary mode of transmission in that outbreak.

Chickenpox most commonly affects children under age 10, most of whom have mild disease. Only around 7% of cases involve adults over age 20, who are far more likely to experience severe illness. Chickenpox is not sexually transmitted.

Diagnosis

The preferred means of testing both mpox and chickenpox is with a polymerase chain reaction (PCR) test. The test is performed on fluids taken from a sore with a cotton swab. A PCR can detect minute amounts of the virus's DNA (genetic makeup) and is currently the most accurate means of diagnosing both of these viral diseases.

When used correctly, both the mpox PCR and VZV PCR have a sensitivity rate (the ability to correctly detect when a person has a disease) of over 97% and a specificity rate (the ability to correctly detect when a person doesn't have a disease) of 100%.

Even so, healthcare providers can generally diagnose chickenpox based on the looks of the rash, particularly if the child is under 10 and has not been vaccinated. A healthcare provider may also consider whether the person has herpes simplex, a drug reaction, impetigo (a bacterial skin infection), or other viral rashes.

By contrast, if mpox is suspected, a healthcare provider may simultaneously test for other illnesses with similar symptoms, such as chickenpox, herpes, shingles, scabies, syphilis, molluscum contagiosum ( an infection caused by a poxvirus), and hand, foot, and mouth disease (a mild, contagious infection common in children).

Treatment

The treatment approach for mpox and chickenpox are similar. For people with mild disease, the treatment is mainly focused on managing symptoms.

This may include using oral pain relievers, topical steroids, and topical anesthetics to help ease the pain. Oral antihistamines, calamine lotion, petroleum jelly, and colloidal oatmeal may help relieve itching.

If a person is at risk of severe illness or complications, antiviral drugs may be used. With that said, the types of antiviral drugs and indications for treatment vary significantly for mpox and chickenpox.

Mpox Treatment

When needed, mpox is treated with an antiviral drug known as Tpoxx (tecovirimat). The drug was first used to treat smallpox and comes in both an oral formulation (taken by mouth) and an intravenous formulation (delivered into a vein).

Tpoxx is generally reserved for these two groups with a high incidence:

• People with severe symptoms, including those with encephalitis (brain inflammation), mpox eye infections, or widespread severe outbreaks of lesions (in which the risk of bacterial infections and sepsis is high)
• People in whom scarring may be harmful, including those with lesions on the pharynx (windpipe) who may develop swallowing or feeding problems, or those with genital or rectal lesions that may interfere with urination or bowel movements

Chickenpox Treatment

When needed, chickenpox is most commonly treated with the antiviral drug Zovirax (acyclovir). It is typically given in an oral form and works best if taken within 24 hours of the rash outbreak. This is especially true in adults who tend to have more severe symptoms.

Zovirax is recommended for the following groups with chickenpox:

• Otherwise healthy people older than 12
• People with chronic skin diseases like psoriasis or eczema
• People with chronic lung diseases like chronic obstructive pulmonary disease (COPD)
• People on long-term salicylate therapy for arthritis
• People on long-term steroid therapy for autoimmune or inflammatory diseases
• People who are pregnant
• People with weakened immune systems

Prevention

Vaccines are generally the best ways to prevent infectious viral diseases like mpox and chickenpox. And, while there are vaccines for both, they are used differently.

For those who are unvaccinated, other preventive measures are needed.

Mpox Vaccination

JYNNEOS is a two-dose vaccine that can protect against mpox. The shots are given four weeks apart. Both shots are needed to provide optimal protection.

Because the duration of JYNNEOS is unknown, it is generally recommended for adults at the greatest risk of exposure. In the United States, that includes:

• Men who have sex with men (MSM) or transgender, nonbinary, or gender-diverse people who have had more than one sex partner in the past two weeks
• Men who have sex with men (MSM) or transgender, nonbinary, or gender-diverse people who have had a sexually transmitted infection (STI) in the past six months
• Anyone who has had sex with someone with mpox in the past two weeks
• Anyone who anticipates being among the above populations

Note that while Verywell aims to use inclusive language, when citing health authorities or research, the terms for sex or gender from those sources are used.

Chickenpox Vaccine

The chickenpox vaccine is a common childhood vaccine given in two doses to children under age 13. Anyone over 13 who hasn't been vaccinated should also get two shots.

There are two vaccines: Varivax (varicella virus vaccine live), which protects against chickenpox alone, and ProQuad, which protects against chickenpox as well as measles, mumps, and rubella. When used as directed, chickenpox vaccines are up to 98% effective in preventing the disease.

While the chickenpox vaccine can provide lifelong protection against chickenpox, another two-dose vaccine called Shingrix (recombinant zoster vaccine) is recommended for adults age 50 and over to prevent the reactivation of VZV and an outbreak of shingles.

Other Prevention Tips

Beyond vaccines, the best way to avoid mpox and chickenpox is to avoid people with mpox and chickenpox. This is sometimes easier said than done.

With mpox, it is important to avoid skin-to-skin contact with someone who has a rash that looks like mpox, including sex partners. You also need to avoid sharing utensils, personal care items, clothing, bedding, and towels with someone who has mpox and to wash your hands frequently with soap and water or an alcohol-based hand sanitizer.

With chickenpox, the same rules apply. But because the virus is so much more contagious, people with chickenpox need to be isolated until the symptoms fully resolve. Disposable gloves and face masks should be worn around the sick individual, and all surfaces (including door knobs) should be regularly sanitized.

Summary

Mpox and chickenpox may look the same but are caused by two different viruses. While both can be passed by skin-to-skin contact, chickenpox can also be spread via the air, and mpox is commonly spread through sexual contact.

The symptoms of mpox and chickenpox are also similar, but mpox tends to be longer-lasting and causes swollen lymph nodes.

Mpox and chickenpox are treated with different antiviral drugs, which are typically reserved for people with severe symptoms or at risk of severe complications. While there are vaccines for both mpox and chickenpox, the mpox vaccine is reserved for adults who have a high prevalence toward acquiring the infection. The chickenpox vaccine is recommended for everyone, especially as part of childhood vaccinations.