Latest on Mpox: What to Know

The World Health Organization (W.H.O.) recently declared mpox a public health emergency of international concern, noting a rise in cases in the Democratic Republic of the Congo and a growing number of countries in Africa. It’s the second time since July 2022 that the W.H.O. has given this designation to mpox.

“Mpox is a viral disease that causes a skin rash similar to chickenpox or shingles,” says Dr. E. Yoko Furuya, chief epidemiologist and medical director of Infection Prevention and Control for NewYork-Presbyterian Hospital. There are two forms of mpox, the more serious clade I, which causes people to get severely sick or die, and clade II, which occurs more regularly.

The rise in cases has mainly been due to the spread of a new strain of clade I, called 1b, which has the potential to spread more across countries in Africa, according to the W.H.O., and possibly outside of the continent. Recently, Sweden reported a case — the first one to be detected outside the African continent — that was caused by the variant. To date, there have been no cases of mpox clade I in the United States and public health risk from this type of mpox strain remains low, said the Centers for Disease Control and Prevention (CDC).

In the past few years, there have been outbreaks of clade II in the U.S. While cases have declined, they continue, and the CDC recommends for people at risk of contracting the virus to follow protective measures. The Department of Health and Mental Hygiene in New York City, which has been the epicenter of the mpox outbreak in the past in the U.S., said they continue to emphasize the importance of vaccinations and encourages people at risk to get the vaccines, which consist of two doses, if they have not done so yet.

“There may risk for a resurgence in cases, so it is important for people to get vaccinated, to know that mpox is still out there, and to get tested if they have symptoms,” says Dr. Jason E. Zucker, an infectious disease physician at NewYork-Presbyterian/Columbia University Irving Medical Center.

Dr. Furuya and Dr. Zucker explain what to know about the vaccines and where people can get the shots. They also share what to know about the mpox virus, including its symptoms and available treatments.

What do we know about the status of cases in the U.S.?
Dr. Furuya: As of August 16, the U.S. has had over 30,000 confirmed cases, according to the CDC, of which 4,528 have been reported in New York, the state with the second highest number of cases.

Many of the cases happen to be spread 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 spread 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 the cases are occurring within these social networks.

Dr. Zucker: While the vast majority of those who have been diagnosed to date with the mpox virus are men who have sex with men, anyone can get and spread mpox.

What are the symptoms of mpox?
Dr. Furuya: People infected with human mpox 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.

Outbreaks in the past few years have shown that 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 effective is the vaccine for mpox, and where can someone get the two-dose shots? How can people get tested for mpox?
Dr. Furuya: Vaccines developed against smallpox are effective in preventing mpox infection. Data from the CDC shows that one of the vaccine formulations, called JYNNEOS, is 75% effective after one dose and 86% effective after the second dose.

JYNNEOS is available through local health departments, public health clinics, and hospitals. It is a series of two injections given four weeks apart. The New York City Department of Health and Mental Hygiene (NYCDOH) states that the JYNNEOS vaccine can be administered to:

• People of any sexual orientation or gender identity who have or may have multiple or anonymous sex partners or participate or may participate in group sex.
• People of any sexual orientation or gender identity whose sex partners are eligible per the criteria above.
• People who know or suspect they have been exposed to mpox in the last 14 days.
• Anyone who considers themselves to be at risk for mpox through sex or other intimate contact.

More information is available on the NYCDOH mpox site and people can find their nearest vaccination site in its vaccine location finder.

Dr. Zucker: If people are experiencing symptoms, they should contact their healthcare provider who can test for mpox. People in New York City can also call 311, where they can be connected to providers who can get check for symptoms and order tests for mpox. In addition, the NewYork-Presbyterian Comprehensive Health Program’s Sexual Health Clinic and New York City Department of Health Sexual Health Clinics are available for testing and vaccination.

It is important for people to get vaccinated and to know that it takes two to three weeks for the vaccines to work. Additionally, it is possible that some people may still get mpox even after vaccination, but it is likely that vaccination makes it less severe. It is also important to know that just being vaccinated does not necessarily mean people no longer have to worry about mpox.

How contagious is mpox?
Dr. Furuya: Mpox 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. Mpox 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.

How serious is it?
Dr. Furuya: Mpox 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 has spread in the U.S. is a relatively mild one.

Dr. Zucker: Mpox can cause extremely painful, uncomfortable, and unpleasant symptoms, but the virus has a very low hospitalization and mortality rate. So far there have been approximately 58 deaths reported out of 32,063 cases in the U.S.

How is mpox treated?
Dr. Furuya: Most people with mpox virus infection have a mild illness that resolves on its own without specific treatment. However, because mpox and smallpox belong to the same family of viruses, there are treatments that have been developed for smallpox that can be used to treat mpox 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. 

Dr. Zucker: An ongoing clinical trial is evaluating the effectiveness of the antiviral tecovirimat for the treatment of mpox in adults and children with mpox infection in the U.S. The clinical trial consists of 73 study locations, including NewYork-Presbyterian/Columbia University Irving Medical Center and NewYork-Presbyterian/Weill Cornell Medical Center, and aims to enroll more than 500 people nationwide.

How concerned should the public be?
Dr. Furuya: Mpox infections in the U.S. continue, but unlike COVID-19, the mpox 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.