What To Know About Human Monkeypox Virus

Infectious diseases experts explain the origins and symptoms of the viral disease and the latest on the current monkeypox outbreak.

monkeypox virus

In July, the World Health Organization (WHO) declared monkeypox a “public health emergency of international concern.” Since the first case of this outbreak was reported in May, more than 28,000 cases across 88 countries have been confirmed worldwide, according to the Centers for Disease Control and Prevention (CDC) as of August 5.

“Human monkeypox virus is a viral infection that can cause a skin rash similar to chickenpox or shingles,” says Dr. Yoko Furuya, chief epidemiologist and medical director of Infection Prevention and Control for NewYork-Presbyterian Hospital. “It was first identified in the 1950s from a colony of sick monkeys, hence the name.”

In the United States, cases have also continued to rise, and on August 4, the Biden administration declared monkeypox a public health emergency, allowing public health agencies to direct money toward vaccines and drug strategies and to utilize emergency funding.

Dr. Jason Zucker

Dr. Jason Zucker

“The declaration of the public health emergency is an important acknowledgement of just how serious things have become,” says Dr. Jason Zucker, infectious diseases specialist at NewYork-Presbyterian/Columbia University Irving Medical Center. “This will hopefully allow public health agencies at both the federal and local levels to have the resources needed to tackle this disease.”

Drs. Furuya and Zucker explain what to know about the current outbreak, including the symptoms, the treatments, and the availability of vaccines.

What is human monkeypox virus?
Dr. Furuya: Human monkeypox virus is part of the same family of viruses as the variola virus that causes smallpox. It has been known to cause infections in humans since the 1970s, and it has mostly been seen in Central and West Africa in people who had contact with animals like monkeys, squirrels, and other rodents. Up until this current outbreak, most infections outside of these African countries have been travel-related.

What do we know about the current rise in cases?
Dr. Furuya: As of August 9, the U.S. had about 9,500 confirmed cases, of which the greatest number have been reported in New York, at more than 2,100.

In this current outbreak, many of the cases happen to be spreading among social networks of people who self-identify as gay or bisexual and other men who have sex with men. Because many cases appear to be spreading through close, intimate contact within these social networks, people are often developing skin lesions localized to the genital, anal, and groin areas, and these can mimic sexually transmitted infections like syphilis and genital herpes. However, anyone in close contact with an infected person could get infected, and not all of the cases are occurring within these social networks.

Dr. Zucker: While the vast majority of those who have been diagnosed to date with human monkeypox virus are men who have sex with men, it is important to know that anyone can get and spread monkeypox. There have been a small number of secondary infections in children and women. In these cases, they were in close contact with someone who tested positive for human monkeypox virus. It is believed that the disease may be more severe in children under 8 and may lead to worse outcomes in pregnant women. For these reasons, we all have to pay attention and remain diligent.

Dr. Yoko Furuya, expert on Omicron subvariant BA.2 and monkeypox

Dr. Yoko Furuya

What are the symptoms of monkeypox?
Dr. Furuya: People infected with human monkeypox virus classically develop a skin rash that can appear anywhere on the body and can look just like red spots or bumps on the skin but can also then develop into fluid-filled skin lesions (what we call vesicles or pustules) like chickenpox or shingles. Sometimes before the rash develops, people can have a fever, chills, or swollen lymph nodes, and people can also have spots that appear inside the mouth and throat. That being said, in the current outbreak many people have had slightly different symptoms than what was seen historically, including sometimes very few skin lesions, sometimes just in one part of the body like the genital area. When this happens it can be mistaken for sexually transmitted infections like herpes or syphilis.

Dr. Zucker: The incubation period is up to 21 days, which means it can be up to 21 days after an exposure before you see any symptoms. Patients are no longer infectious only after their sores have scabbed over, those scabs have fallen off, and new skin has grown in its place. This process can take up to four weeks.

How contagious is monkeypox?
Dr. Furuya: Monkeypox can be spread from either infected people or infected animals, most commonly by direct contact with the rash, scabs, or body fluids. Alternatively, direct contact with material like clothing or linens that have been in contact with the infectious rash or body fluids can spread the viral disease. Monkeypox can also spread from respiratory secretions or saliva, but, unlike COVID-19, transmission requires more prolonged, face-to-face contact or intimate physical contact. Finally, infected pregnant people can spread the virus to their fetus through the placenta.


“People infected with human monkeypox virus classically develop a skin rash that can appear anywhere on the body and can look just like red spots or bumps on the skin but can also then develop into fluid-filled skin lesions (what we call vesicles or pustules) like chickenpox or shingles.”

— Dr. Yoko Furuya

How serious is monkeypox?
Dr. Furuya: Monkeypox generally causes a skin rash, and sometimes a fever, chills, and swollen lymph nodes. These are usually mild, but they can cause a lot of discomfort, and sometimes the skin lesions can be more significant. There are other strains of the virus that can cause more severe illness, but the one that is currently spreading in the U.S. and other countries is a relatively mild one. Most infected people do not need treatment and get better on their own.

Dr. Zucker: Monkeypox can cause extremely painful, uncomfortable, and unpleasant symptoms, but the virus has a very low hospitalization and mortality rate. So far there have only been approximately 10 deaths reported during this outbreak out of almost 27,000 reported cases.

How is monkeypox treated?
Dr. Furuya: Most people with monkeypox virus infection have a mild illness that resolves on its own without specific treatment. However, because monkeypox and smallpox belong to the same family of viruses, there are treatments that have been developed for smallpox that can be used to treat monkeypox if infections are more severe, or if the infected person has a weakened immune system and therefore is at higher risk of developing a more severe illness. These treatments include certain antiviral drugs such as tecovirimat. 

“My two most important messages to the public are: if you have lesions, get tested right away; and if you’re at risk, get vaccinated and check yourself regularly for any evidence of infection.”

— Dr. Jason Zucker

Is there a vaccine for monkeypox?
Dr. Furuya: Vaccines developed against smallpox are effective in preventing monkeypox infection as well, with previous data from Africa showing that they are at least 85% effective in preventing monkeypox infection. One of the vaccine formulations, called JYNNEOS, is available through the CDC and local health departments to be given to people if they have had a high-risk exposure to someone with monkeypox. It is a series of two injections given four weeks apart.

Additionally, the New York City Department of Health and Mental Hygiene (NYCDOH) has opened clinics to administer the vaccine (two-dose JYNNEOS) to gay, bisexual, transgender, gender-nonconforming, or gender-nonbinary people, and men who have sex with men who have had multiple or anonymous sex partners in the last 14 days and are age 18 and older. More information and online appointments are available on the NYCDOH Monkeypox site.

Dr. Zucker: The vaccine currently being distributed is approved for smallpox and human monkeypox virus. It takes 2 to 3 weeks to work, so it’s important that people know that just being vaccinated does not necessarily mean you no longer have to worry about monkeypox.

How concerned should the public be?
Dr. Furuya: Monkeypox infections in the U.S. are definitely on the rise, but unlike COVID-19, the monkeypox virus does not seem to spread easily between people without close contact, so the risk to the general U.S. population is still low at this time.

Dr. Zucker: My two most important messages to the public are: If you have lesions, get tested right away; and if you’re at risk, get vaccinated and check yourself regularly for any evidence of infection.

Like any other transmissible disease, we need to have open dialogue and conversations, share accurate information, and give people easy access to care so they can take the necessary steps to get tested and treated and help protect others.

We will overcome this public health challenge, but we will need everyone’s help and diligence to do so.