What is Monkeypox? How do you catch it? Is there a vaccine?

Reeti Khare, Ph.D., discusses pressing questions about monkeypox symptoms, transmission dynamics, prevention and treatment strategies, and basic virology.

Reeti Khare, Ph.D., discusses pressing questions about monkeypox symptoms, transmission dynamics, prevention and treatment strategies, and basic virology.

Reeti Khare, Ph.D., Clinical Microbiologist, National Jewish Health and author of the Guide to Clinical and Diagnostic Virology, joined the ASM Studio at ASM Microbe 2022 to discuss pressing questions about the symptoms, transmission dynamics, prevention and treatment strategies and basic virology of monkeypox.

What is Monkeypox?

Monkeypox is an infection caused by the Monkeypox virus. It is a cousin of the variola virus, the pathogen that causes smallpox.

How do monkeypox and smallpox compare?

Clinically, smallpox and monkeypox can be very similar. Both can cause fever, chills, headache, muscle aches, and fatigue. But there are a few differences between the 2 viruses that are really important to remember.

Smallpox has a higher death rate than Monkeypox

The biggest difference is the death rate. Smallpox has a mortality rate of up to 50%, while monkeypox comes nowhere close. There are 2 types of monkey pox. The strain implicated in the 2022 outbreak is the West African strain, with a mortality rate of about 1%. The other species, the Congo Basin Strain, has a higher mortality rate of up to 10%.

Monkeypox and smallpox produce similar rashes

One symptom shared by the 2 viruses is a characteristic rash that looks like raised bumps over the skin. Over the course of 4-5 days, the bumps fill with fluid and pus and become pustules. Monkeypox and smallpox pustules are both characteristically umbilical, meaning they have a small divot in the middle. Over the course of 2-3 weeks, pustules will ulcerate, crust over and fall off.

Another feature of these poxvirus pustules is that they all occur at the same stage. In other words, all monkeypox and smallpox lesions generally appear together, umbilical, ulcerate and fall off together. This can be especially useful when trying to distinguish between other smallpox viruses. For example, chickenpox, caused by the varicella zoster virus, causes lesions that develop at different stages of the disease. New lesions can form at the same time that others are already ulcerating.

Many viruses can cause skin rashes, so another way to distinguish them is to look at their distribution pattern across the body. Monkeypox and smallpox tend to be more centrifugal. That means the lesions usually appear on the extremities and face. Sometimes lesions even appear on the palms and soles of the feet and can spread all over the body.

Chickenpox is essentially the opposite. It has a more centripetal distribution, with most lesions occurring mostly on the trunk and face, and fewer lesions on the extremities. Measles and rubella have a bulk distribution, with most lesions appearing on the face and then decreasing in concentration as one moves further in the body.

Monkeypox infects both humans and animals

Although monkeypox can be acquired from other humans, the disease is generally acquired from animals. The virus can infect monkeys, rodents and other small animals, and this animal reservoir is really important because it makes the virus difficult to eradicate.

Smallpox has only one host: humans, and thanks to significant global public health efforts to vaccinate and reduce person-to-person transmission, we were able to eradicate smallpox in 1980. Poliovirus is another good example of this.

How Is Monkeypox Diagnosed?

Monkeypox lesions are actually the best way to test for the virus. Lesion fluid or tissue samples are collected with a swab or directly in viral transport media and then tested by PCR. Shole blood doesn’t work very well for diagnosis.

While some US labs are able to perform PCR analysis, using a general orthopoxvirus assay, positive samples are sent to the US Centers for Disease Control and Prevention (CDC) for confirmatory testing.

Where does Monkeypox come from?

Until recently, monkeypox was mainly restricted to a few West African and Central African countries. That doesn’t mean it wasn’t seen anywhere else. In 2003, there was even a major outbreak in the US, mainly in the upper states of the Midwest. Animals had been brought in from Africa to be sold as exotic pets, and monkeypox hitched a ride. The virus was then transmitted from the exotic animals to prairie dogs housed in the same facility, and when those prairie dogs were sold as pets, the virus was transmitted to humans through bites, handling and/or cleaning of the bedding and cages of infected animals.

How is Monkeypox transmitted?

Notably, none of the cases in the 2003 outbreak were attributed to human-to-human transmission, but on May 7, 2022, the World Health Organization (WHO) began reporting the spread of monkeypox in non-endemic countries. As of the date of this call, June 10, 2022, more than 1,000 cases had been reported in nearly 30 countries. Many infected individuals in this outbreak reported no travel or animal exposure, indicating a significant human-to-human transmission element.

Human-to-human transmission of monkeypox mainly occurs through direct contact with monkeypox pustules. However, the virus can be transmitted through other body fluids, for example, respiratory droplets and other aerosols, as well as fomites contaminated with that infected lesion fluid or body fluid.

Oral and anogenital lesions have been reported more frequently in this outbreak, and we have seen a higher frequency of infection in men who have sex with men. Still, we don’t really know whether this virus is transmitted through close intimate contact, or whether it is really transmitted through sexual bodily fluids, and this is a topic that is still being researched.

Will Monkeypox be the next pandemic?

Hopefully not. Monkeypox is a DNA virus, meaning it replicates much more slowly than RNA viruses, such as the flu or SARS-CoV-2. This slow evolution, along with viable treatment/prevention options, is likely to limit the spread of disease.

How is Monkeypox prevented and treated?

The story of the smallpox vaccine is a legend. Edward Jenner noted that milkmaids exposed to cowpox did not get the deadliest of smallpox, leading to the first vaccine. Fortunately, the smallpox vaccine is also cross-protective against monkeypox – about 85%.

A number of antivirals have also been tested against monkey pox. Tecovirimat is a smallpox-specific antiviral that prevents the poxviruses from leaving the cell, and cidofovir has been tested in animals and shown to be effective. If all these things are in place, before an outbreak starts to get crazy, we’re definitely in a better position than we were with the rise of COVID-19.

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