Emerging from the Orthopoxvirus genus of the Poxviridae family, monkeypox is a rare disease caused by the monkeypox virus (double-stranded DNA virus) which was first discovered in 1958 whereas, the first human case was recorded in 1970 and since then the infection has been reported in a few central and western African countries.
Monkeypox is a viral zoonosis with symptoms like smallpox (caused by the variola virus, part of the same family Poxviridae family) and chickenpox but it is currently less fatal.
Symptoms and Transmission
Fever, headache, myalgia, fatigue, and lymphadenopathy are initial symptoms of Monkeypox.
Additionally, some unexpected or unusual spots, ulcers, and blisters can develop anywhere on the body (including the face, hands, pubis, and genitals) which can be like chickenpox, anogenital herpes, or syphilis.
However, unlike chickenpox, the patient develops a rash within 1 or 3 days on the face and then spreads to other parts of the body. Sometimes, flu-like symptoms appear before the rash.
This can be transmitted from person to person (via direct contact with monkeypox skin lesions or scab), coughs or sneezes of a person with the monkeypox rash, or in contact with infected rodents (such as rats, mice, and squirrels).
Animal-to-person transmission occurs through broken skin, like from bites or scratches, or with an infected animal’s blood, bodily fluids, or pox lesions (sores).
The number of cases is increasing in Africa and countries with no sign of disease before.
Most of the confirmed monkeypox cases are subjects with travel history to countries in Europe and North America, rather than West or Central Africa where the monkeypox virus is endemic.
In 2003, the first outbreak outside of Africa was seen in Texas, USA.
2022 brought outbreaks to many countries in the Americas, Europe, North Africa, the Middle East, and Australia which had reported more than 350 cases of the disease (both suspected and confirmed).
Treatment and Vaccines Approval
The two commonly used vaccines during the monkeypox outbreak are ACAM2000 or Vaccinia and JYNNEOS or Modified Vaccinia Ankara (MVA) vaccine (approved by FDA and EMA, also known as Imvanex or Imvamune), both were originally developed for smallpox and made available to use for monkeypox since both share the same genetic code whereas no data is available on the clinical efficacy or effectiveness of these vaccines.
Recently, European Medicines Agency (EMA) has approved the usage of Imvanex (non-replicating smallpox vaccine) in Europe under exceptional circumstances to protect adults from catching the virus in all European Union Member States as well as in Iceland, Liechtenstein, Norway, and Bavarian Nordic.
The vaccine has also gained regulatory approvals in Canada (marketed as Imvamune) and the U.S. (marketed as Jynneos).
ACAM2000 delivers a live Vaccinia virus into the skin through skin pricking, whereas JYNNEOSTM transmits a non-replicating live virus over a period of four weeks (two subcutaneous injections).
However, people with one dose of JYNNEOSTM are not considered vaccinated until 2 weeks after receiving the second vaccination dose since it is considered as a two-dose vaccine.
The Advisory Committee on Immunization Practices (ACIP) decided to vote for JYNNEOS pre-exposure prophylaxis (PrEP) as an alternative to ACAM2000 for individuals at risk for orthopoxvirus exposure. ACAM2000 is a single-dose vaccine and has more side effects than JYNNEOS.
Imvanex must be injected subcutaneously (two 0.5 ml doses, with the second dose given at least 28 days after the first in case of no prior vaccination against the vaccinia virus). It contains modified vaccinia virus Ankara in an attenuated (weakened) form, hence helping the body resist variola (smallpox), monkeypox, and vaccinia virus infections.
It can cause side effects including headache, nausea, myalgia (muscle pain), fatigue, and adverse responses at the injection site (pain, redness, swelling, hardening, and itching). If an individual is still in danger of contracting smallpox, monkeypox, or other orthopoxviruses, a booster dosage is also advised every two to ten years.
With increasing cases of monkeypox, additional vaccines are approved by different regulatory bodies such as:
• NHS which is also offering smallpox (MVA) vaccination to people exposed to monkeypox
• U.S. Food and Drug Administration (FDA) which also licensed two vaccines manufactured by Emergent BioSolutions and Bavarian Nordic (uses a non-replicating form of vaccinia). Besides, there are some antiviral medications licensed by FDA for the treatment of
o Tecovirimat (also known as TPOXX, ST-246)
o Vaccinia Immune Globulin Intravenous (VIGIV)
o Cidofovir (also known as Vistide) and
o Brincidofovir (also known as CMX001 or Tembexa)
Monkeypox is yet another zoonosis affecting Mankind’s safe existence and welfare across the world. However, with the rapid approval and availability of the above treatments, it is possible that the exposure to harm from the current variants will be diminished.