Monkeypox: CDC Raises Travel Alert, But How Much Threat Is it Really?

Kevin Kavanaugh, MD

Many individuals are wondering should they be concerned about monkeypox, or is it just a disease of the week, soon to pass and be forgotten. Current data indicates the former. Cases in the United States have quickly risen, now at 25 confirmed cases and many more cases are expected to have occurred but not been detected. Worldwide, the number of confirmed and suspected cases has risen to nearly 1000, and the spread is continuing. The virus is currently in 29 countries. The Centers for Disease Control and Prevention (CDC) issued raised the travel alert to a Level 2 today.
 
All of this sounds ominous, but this is a virus we know, and its spread should be able to be controlled. However, this epidemic will not stop by itself, and the public health agencies need to act. Last week the World Health Organization held a two day webinar which outlined what is known about the Monkeypox outbreak and the main questions which still need answering. Below is some of the information presented in the webinar:

Monkeypox is an orthopoxvirus and related to smallpox. There are two main strains: A Central African and Western African clade. The Central African has a fatality rate of up to 10%, and the West African has a fatality rate of between 2 to 3%. Luckily, the current virus circulating in Europe is related to the West African Clade.
 
The wild-type virus has relatively low transmissibility. Dr. Paul Fine from the London School of Hygiene and Tropical Medicine pointed out that unvaccinated individuals living in the same household with an active Monkeypox case have only a 10% to 15% chance of secondary transmission. This compares to smallpox which has a 40% to 50% intrahousehold attack rate.

Although human-to-human transmission has been reported in Africa, it has rarely, if ever, been previously reported in countries where the virus is not endemic. The first human case of monkeypox was detected in the Basankusu Villae, Equateur province in the Dominican Republic of the Congo in 1970. This followed the global smallpox eradication. At that time almost everyone had received the smallpox Vaccine which also has an 85% efficacy rate for monkeypox in recently vaccinated individuals. But in the 1980s, vaccination for smallpox stopped, and worldwide immunity since then has waned.
 
Dr. Emmanuel Nakoune-Yandoko, Institut Pasueur de Bangui, Central African Republic, presented data that after 2013, cases of monkeypox have steadily increased. Up to the year 2021, there were 40 outbreaks all consisting of between 1 to 25 confirmed and suspected cases.A suspected zoonotic (animal) source was able to be documented in 16 of the 40 outbreaks. Human transmission was described in 65.7% of the cases, but 95.2% of this transmission was intrahousehold (where there would be expected a high degree of close contact with the infected individual). 53% of the cases were female. However, young boys were at increased risk, presumably because they participated in hunting wild animals and thus, were at increased risk for zoonotic transmission. Dr. Ifedayo Adetifa from the Nigeria Centre for Disease Control, reported that In Nigeria, there has been a 50-year history of monkeypox, but there was a 40-year silent period with a resurgence of the disease in the last 5 years.

The virus frequently infects a wide range of mammals. Monkeypox was first detected in 1858 with 2 outbreaks in monkey colonies, hence its name “monkeypox.” However, the exact animal host is not known. Professor Dimie Ogoina, FACP, Niger Delta University reported that animal exposure was identified in 10 cases (8.2% of the total) and consisted of 2 monkeys, 2 rodents, 2 unidentified wild animals, and 4 domesticated animals. None of the animals were dead or appeared sick. Dr. William Karesh from the World Organization for Animal Health stressed the importance of rodents and that African Squirrels are the main suspect for a major monkeypox reservoir. This suggestion underscores the need for proper disposal of medical waste to prevent the disease from spreading to rodents which frequently inhabit dumps and waste disposal areas.
 
The clinical presentation of monkeypox is similar to chickenpox (which is not related to orthopoxviruses) and secondary syphilis. In the Central African Republic, there were just as many outbreaks from smallpox as from monkeypox. Dr. Professor Dimie Ogoina, FACP, Niger Delta University, reported that 100% of patients had skin lesions and 88% had fever. Lymphadenopathy and myalgia occurred in approximately 60% of cases, sore throat in 57%, cough in 30% and headaches in 21%. Of the skin lesions, 66% involved the genitalia (See figure). In Nigeria, the incubation period for monkeypox was reported to be 3 to 34 days, the mean is 9.5 days.
 
Monkeypox readily affects children. In some outbreaks, children have made up the majority of cases. In the Central African Republic children, the case fatality rate for monkeypox is 7.5% but in children it is 9.6%.
 
However, the current outbreak in Europe presents a very different picture. Dr. Gianfranco Spiteri from the European Center for Disease Control presented data on 373 cases which were reported to the European Union since May 18, 2022. Most cases had lesions on their genitalia or peri-genital areas at the time of presentation. So far, no case has resulted in death. In addition, epidemiological links to Western or Central Africa have not been identified. Of the 91 cases reported to EpiPulse, 88 (100% of those reporting data) were male and 45 (100% of those reporting data) reported MSM (Male sex with Males).

Similar findings were reported in the United Kingdom. Professor Isabel Oliver of the United Kingdom’s Health Security Agency reported three outbreaks. The first two were small, consisting of one and three cases. The first had one case of secondary transmission and the second was a family cluster. The third incident consisted of 190 cases. All cases were male except 2 which were associated with the two previous incidents. The age range was between 20 to 49 and 110 were known to be gay and bisexual men who have sex with men. Most cases were mild.

Currently, the cases of monkeypox appear to be caused by sexual activity at two recent “Raves” which took place in Europe.
 
Although it appears close contact is required for transmission, it is unclear if asymptomatic spread through body fluids can occur during the disease’s prodromal period. It is not known if the virus is in semen. It is not known if this is primarily a sexual disease. It is also not known if the virus can spread via fomites (environmental surfaces), but unlike SARS-CoV-2, orthopoxviruses are fairly stable in the environment. Unlike SARS-CoV-2, airborne transmission is not felt to be a major mode of spread. 

The orthopoxvirus is a DNA virus, which has a lower rate of mutations than RNA viruses. The WHO webinar reported that the strain circulating in Europe is related to the West African Strain but has 47 new mutations. However, the significance of these new mutations is not known. In the United States, two strains have been detected, suggesting the virus has been circulating in the community undetected for some time.
 
Where this disease came from will probably be a mystery. Already, there are theories of biolabs and germ warfare circulating on social media. However, the history of this disease shows an increasing incidence in Africa, presumably from waning immunity. At this point, we must be vigilant, but so far human-to-human spread of this virus appears to be related to risky behavior and very close physical contact. There are both vaccines and antiviral medications which are effective against orthopoxviruses. In addition, epidemiological case tracking and public education are expected to bring this outbreak under control.