Monkeypox – It's back - How dangerous is it, and what should we do about it ?

This blog was originally compiled at the time of the Monkeypox epidemic in 2022. A new and more infectious variant of MPox which also has a higher fatality rate, has now hit Africa, and looks as though it may be coming our way. Young children are particularly hard-hit by this variant of the virus.

Read on to find out more about how the last epidemic developed, and see also the update compiled this month at the end of the article....hopefully this will provide some insight into what we should expect in UK.

There has been much speculation in the media recently about the current Monkeypox outbreak – not surprisingly perhaps, in view of our recent experience with Covid…

Some pundits are even predicting that this could be the fore-runner of the next pandemic  - how realistic a view is this, and should we be worried ?

Looking at the evidence objectively, at present the answer to both questions is: Not very so far….but we should not be complacent.

First, let’s look at the nature of the virus that causes the illness, and its origins and recent epidemiology.

The causative agent is a close relative of the much more notorious smallpox virus, which caused widespread suffering and countless deaths throughout the world before its eradication in 1980 (1). It is an enveloped double-stranded DNA virus that belongs to the Orthopoxvirus genus of the Poxviridae family. Like the Covid virus, and probably most other existing human viruses, it origin is zoonotic  i.e. it was originally transmitted from animals to humans. 

Animal species so far identified as Monkeypox hosts are varied and include rope squirrels, tree squirrels, Gambian pouched rats, dormice, non-human primates and other species; there have been many outbreaks in the human population since the original one in 1970, but the exact origin of each specific outbreak is often difficult to determine. The disease was first identified in humans in the Democratic Republic of the Congo (DRC) in a region where smallpox had been eliminated in 1968, and it is not thought to have originated from the smallpox virus directly.

Monkeypox is a disease of global public health importance as it not only affects countries in west and central Africa, but the rest of the world. In 2003, the first Monkeypox outbreak outside of Africa was in the United States of America and was linked to contact with infected pet prairie dogs. These pets had been housed with infected Gambian pouched rats and dormice that had been imported into the country from Ghana.

More recently, outbreaks of Monkeypox have been reported in travellers from Nigeria to Israel in September 2018, to the United Kingdom in September 2018, December 2019, May 2021 and May 2022, to Singapore in May 2019, and to the United States of America in July and November 2021. In May 2022, multiple cases of Monkeypox were identified in several  countries where the virus was non-endemic. This was atypical for the virus, whose spread is normally associated with travel between continents. Studies are currently underway to  understand further the epidemiology, sources of infection, and transmission patterns. Although case numbers are relatively small to date, it is now evident that the disease is now spreading in a number of territories, including UK, independently of foreign travel.

Human-to-human transmission can result from close contact with respiratory secretions, skin lesions of an infected person or recently contaminated objects. Transmission via droplet respiratory particles usually requires prolonged face-to-face contact, which puts health workers, household members and other close contacts of active cases at greater risk. The incidence of human transmission has risen in recent years - this may reflect declining immunity in all communities due to cessation of smallpox vaccination. Close physical contact is a well-known risk factor for transmission. Although the disease isn’t exclusively a sexually-transmitted disease (STD), so far the incidence in homosexual males has been higher than in the general population, and heterosexual transmission may also turn out to be a key route of spread as the epidemic progresses.

How does the disease progress and how serious is it ?

The incubation period (interval from infection to onset of symptoms) of Monkeypox is usually from 6 to 13 days but can range from 5 to 21 days. The virus causes generally relatively mild disease in otherwise healthy individuals, with initial symptoms of fever and lymph node swelling giving way to rashes and skin eruptions, primarily on the face and extremities. The disease usually self-limiting without anti-viral treatment, with the symptoms generally lasting from 2 to 4 weeks.

Severe cases occur more commonly among children and are related to the extent of virus exposure, patient health status and nature of complications. Underlying immune deficiencies may lead to worse outcomes. Although vaccination against smallpox was protective in the past, those younger than 40 to 50 years of age now (depending on the country) may be more susceptible to Monkeypox due to cessation of smallpox vaccination campaigns globally after eradication of the disease.  Complications of Monkeypox can include secondary infections, broncho-pneumonia, sepsis, encephalitis, and infection of the cornea with ensuing loss of vision. The extent to which asymptomatic infection may occur is so far unknown.

The case fatality ratio of Monkeypox has ranged historically from 0 to 11 % in the general population and has been higher among young children. In recent times, the case fatality ratio has been around 3–6%. It should be noted that this is significantly higher than Covid (ca 1-2% in the general population, but much lower in the fully-vaccinated).

How likely is Monkeypox to progress to a full-blown pandemic ? Although, as already discussed, the fatality ratio is worryingly high as compared with Covid, salvation may lie in the nature of the virus and its relatively low infectivity compared with seasonal respiratory viruses like SARS-CoV-2 and influenza. The other big advantage over Covid is that symptomless transmission has not so far been identified - those infected always present with one or more of the classic symptoms, hence tracking is much more straightforward.

Thanks to the Smallpox eradication programme, we also have approved smallpox vaccines ‘on the shelf’ which we know are effective (against the current Monkeypox ‘variants’ at least) and can even be used to advantage within 5 days after first symptoms appear. Viral spread should also be restricted by pre-induced immunity in the over-40s, many of whom will have been vaccinated against smallpox as children. We also know a lot more about the nature of the virus and ways to manage it than we did about Covid at the start of the pandemic in early 2020.

The main concern is whether zoonotic transmission and the attendant risk of viral mutation will again raise its ugly head and increase the risk of creating another smallpox-like ‘monster’. Most Monkeypox outbreaks in recent years have originated from animal to human transmission. Fortunately double-stranded DNA viruses are far less subject to rapid variant evolution of the sort we saw with SARS-CoV-2. This is because the double-stranded DNA replication mechanism is much more efficient at correcting errors than that used by  the RNA viruses, so the spontaneous mutation rates which normally drive viral evolution are much lower for this genus. 

Set against that, however, is the heightened risk of transmission of the virus to and from pet animal species. The UK, in common with many countries in the developed world, harbours many millions of pet cats and dogs, and these could become a significant problem if cat/dog to human transmission becomes prevalent. This is due to the close contact we naturally have with these animals as pets, and hence the sheer volume of potential transmission events.

So far, mercifully, this issue does not seem to have arisen in UK, but we should not become complacent about the risk, given the implication of pet species in the 2003 USA outbreak. We should remember that viruses are highly adaptable and have a habit of taking advantage of the propensities and behavioural 'weaknesses' of their chosen hosts – in particular their habitual close contacts with animal species, and of course our renewed obsession with personal air travel post-Covid. Their potential to do us harm should never be under-estimated.

What precautions should we take at this stage ?

Much epidemiological research is ongoing regarding the origins of the virus and methods of control. We need urgently to identify what factors are responsible for the switch to more frequent human to human transmission and counter them before the virus gets a chance to spread out of control. Existing smallpox vaccines are being investigated for efficacy against Monkeypox, and new vaccines specific to it are being developed. 

Individuals showing symptoms themselves or who have had recent contacts with confirmed cases, are already recommended by the health authorities to self-isolate for at least 21 days. Pet owners should keep a close eye on their pets’ health and report any symptoms which might indicate pox infection. If the epidemic progresses, it may become necessary to classify the disease as legally notifiable, and this should apply both to humans and to pet species to minimise further zoonotic transmission.

Only time will tell how well we are able to control this outbreak.

Hopefully it will turn out to be an epidemiological ‘damp squib’ and fizzle out in due course….

Update 8.6.22: It has just been announced that the UK authorities have now classified Monkeypox as a notifiable disease, as I suggested they might in yesterday's blog. This demonstrates significant concern that the epidemic could spread out of control. There has been no mention as yet of any requirement for pet species surveillance.

Update 12.6.22: The Monkeypox epidemic does now appear to be spreading quite widely, The progress of the epidemic remains atypical, and this currently defies any satisfactory explanation. 

Vaccination is already recommended in some territories following close exposure to infected individuals, and 'ring' vaccination is also being tested as a way of restricting spread. 

There is an active debate underway as to whether mass vaccination should be implemented to help control the epidemic. Apart from the cost, the main problem with this is that, although we have good stocks of smallpox vaccines, and these are approved for use in the general population, they have not been tested exhaustively against Monkeypox. There are also known side effects, particularly with the 1st and 2nd generation vaccines, which make them unsuitable for children and certain other at risk groups. Supplies of 3rd generation vaccines are at present limited. 

An additional problem is that the disease now has a stigma attached, particularly in 3rd world countries, as a result of its higher incidence among homosexual men. This may hinder efforts at persuading individuals to come forward for vaccination.

Update 23.6.22: Vaccination against Monkeypox using existing smallpox vaccines has now been recommended in UK for some at risk groups, notably homo- and bi-sexual men who are sexually active. The epidemic is still progressing, though not yet out of control.

Update 25.7.22: WHO have just declared the Monkeypox epidemic to be a world health emergency. Although this is largely because of the unexpectedly high rate of spread, (which has to some extent surprised epidemiologists), and the disease remains relatively benign and self-limiting in most cases, it is a worrying development nevertheless. I suspect one of WHO's main concerns is development of new and more Smallpox-like variants. Although this is less likely for a ds-DNA virus than for RNA viruses like Covid, the likelihood of it occurring will inevitably increase with increasing case load. Hence the need for more decisive action....

Update 2.10.22: Looks like we may be winning the fight against this particular epidemic. Case numbers have fallen steadily since the summer peak, due in part by all accounts to changes in behaviour, particularly in the gay and bisexual male community which are the most prone to transmission. We must however remain vigilant to ensure things don't flare up again, and health authorities need to ensure adequate supplies of vaccine remain available. 

See this link for more details.

Update 16.8.24: After a gap of almost 2 years, the Mpox virus (as it's now called) seems to have returned in equatorial Africa with a vengeance. What's more, it has done so in a new and more virulent form with a higher fatality rate, and is starting to trouble the authorities in other states including Kenya and Uganda. There have been over 500 deaths so far and many thousands of identified cases. Young children have been particularly hard hit, especially in areas where nutrition is poor.

The new variant, designated 1B, is of the Clade 1 type. The 2022 outbreak was caused by the Clade 2 type, which is less infectious and also has a significantly lower fatality rate. Infections in Europe and the US in 2022 were mainly spread as an STD by male homosexual and bisexual contact. The new variant is significantly more infectious, and can be transmitted easily by other forms of close contact via body fluids. The greatest concern at present is that the disease is already spreading to large population centres, and risks enveloping the whole continent. Vaccines are in short supply in Africa, and insufficient to control the epidemic in its present form. There are already exhortations to European and US vaccine stock holders to share their current stocks, in order to avoid the issues we saw with Covid vaccine hoarding in the early stages of the pandemic. 

Until a few days ago, there were no reports of the new variant spreading beyond Africa, but several cases have come to light in Pakistan, and one in Sweden. All seem to be in individuals who have recently visited Africa. The rapid spread is now a major concern, given the more infectious nature of this variant of the virus, and uptick in international travel and immigration from Africa to Europe since the Covid pandemic. 

The outbreak has prompted the Africa Centres for Disease Control and Prevention (Africa CDC) to declare its first-ever public-health emergency on 13 August, and the World Health Organization (WHO) made a similar global declaration following its meeting on 14 August.

Although stocks of vaccine in Africa and the 3rd world are low, there is availability in the EU and USA, and I would anticipate there would now be a push to increase stocks in anticipation of a pre-emptive vaccination campaign. Negotiations are already underway with vaccine suppliers. vaccine production takes time, however, and ca 90% coverage is normally required to bring an epidemic under control, so that the million or so doses anticipated by year end may not be available early enough to stem the tide in Africa, or prevent extensive spread to other continents. 

Regarding pet species, there have been no reports of reverse zoonotic transmission of Clade 1B in Africa so far - hopefully this will remain the case. Time will tell, if and when the virus becomes established in UK. I would anticipate human to human transmission will remain the primary concern.

Watch this space for more developments on the 2024 epidemic.......

References:

1)      1) WHO Newsroom Article (19^th May 2022): https://www.who.int/news-room/fact-sheets/detail/monkeypox.

        2) Nature News Article 8.6.22: Monkeypox vaccination begins — can the global outbreaks be contained? See link 

3) Nature News Article Update 13.8.24: Growing mpox outbreak triggers Africa’s first health emergency — and fears of wider spread. https://www.nature.com/articles/d41586-024-02607-y

  

First published: 25.7.22