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Don’t monkey around with the pox

19/9/2018

 
The patient was admitted 3 days after arriving in the UK from Nigeria. He had felt unwell with a fever and generalise aches and pains the day before he travelled. On the morning of admission he had noticed a rash on his left leg as well as tender enlarged lymph nodes in his groin.
 
The admitting Consultant Physician spoke to infection control before the patient arrived and it was decided to admit the patient directly to a negative pressure side-room in the infectious diseases unit without bringing the patient into the main hospital in case this might be a viral haemorrhagic fever. The patient met a diagnosis of low possibility of viral haemorrhagic fever; temperature ≥ 37.5 oC PLUS been in endemic area within 21 days of onset of illness.
The Consultant and Nurses met the infection control team on the ward and the Doctor and Senior Nurse who were going in to see the patient put on personal protective equipment (PPE) before entering the room. PPE included gloves, plastic aprons, fluid repellent surgical face mask and visor.
 
The evaluation of the patient confirmed that they had probably had a fever before admission but that this had now settled and he was afebrile. It also distinguished that the rash was crop of fluid filled vesicles on the left calf and that the inguinal lymph nodes on that side were indeed enlarged and painful. The Consultant told the Microbiologist waiting outside of the room that he thought the rash looked a bit like chicken pox “only different”.
 
The Microbiologists mind started to race. Could this be smallpox?! Small pox had been eradicated in 1980 but it could still be used as a bioterrorist agent.
chickenpox, smallpox, monkeypox
Click for larger image
​The patient was started on Ceftriaxone and Gentamicin to provided broad spectrum cover whilst further investigations where sent, as well as Aciclovir just in case this was a slightly odd presentation of chicken pox in an adult. Blood (serum) and viral skin swabs were taken and in the meantime the Microbiologist rushed back to the office to make some calls and make himself a cup of tea!
 
The first call was to the specialist Imported Fever Service at Porton Down to discuss the possible diagnoses. The second was to Public Health England to make them aware of the possible case.
 
As results came back negative the differential started to be narrowed down, it was looking like this was a pox illness, but which one of the poxvirus diseases, chicken pox (Varicella Zoster Virus), vaccinia (cowpox), or was there an outside chance of smallpox.
 
The patient was cared for in the infectious disease unit and close attention was paid to infection control precautions. The following day the diagnosis was confirmed; the patient had monkeypox!
 
“Really” said the Microbiologists’ colleague “what the heck is monkeypox, you’ve made it up haven’t you… I’ve had enough of you… last week you told me another patient had camel flu and that was actually MERS!!!” she concluded in an exasperated tone.
 
So if you are sitting reading this and wondering … is he pulling our leg (again!)… is monkeypox just made up… then think again.
 
What is monkeypox?
Monkey pox is an acute viral infection caused by the Monkeypox Virus from the same family of Orthopoxviruses which includes smallpox and vaccinia.
 
Monkeypox has been sporadically identified in various countries in West and Central Africa (Cameroon, the Central African Republic, the Democratic Republic of Congo, Liberia and Nigeria). Human infections were first diagnosed in the Democratic Republic of Congo (DRC) in the 1970s, although the virus had been discovered back in 1958 in laboratory macaque monkeys (hence its name).  Since 2017 there has been an ongoing outbreak of monkeypox in Southern Nigeria, with spread to Lagos, Akwa Ibom, Bayelsa, Cross River, Delta, Ekiti, Enugu, Imo, Ibadan, Nasarawa, Niger, Rivers, and the federal capital territory. So far there have been 228 suspected cases. Attempts are being made to control the outbreak but this is difficult as it involves trying to control the natural reservoirs of the virus, rodents and monkeys.
 
Monkeypox is thought to be transmitted through contact with infected animals or their body fluids, possibly through the practice of eating bush meats, or wild animals caught in the forest for food. One such bush meat species is the Gambian pouched rat (Cricetomys gambianus). It is the world’s largest rat; they are omnivorous and can grow to 3ft long including their tail. Apparently Gambian pouched rats can be trained to detect land mines and tuberculosis with their highly developed sense of smell, so they aren’t all bad. The trained pouched rats are called HeroRATS and are cheaper to train than dogs; a rat requires $7,300 for nine months of training, whereas a dog costs about $25,000 for training. Who knew?!
Gambian pouched rat HeroRATS
​However, back in 2003 there was an outbreak in the USA (Illinois, Wisconsin, Indiana and New Jersey) when prairie dogs were infected by an imported Gambian pouch rat (Gambian pouched rats have become an invasive species due to rats being released by exotic pet owners). At least 70 people were infected. Another consequence of taking exotic wild life and sell it for profit… it’s just wrong.
 
Why tell you about monkeypox? Well there have been two cases identified in the UK within the last two weeks related to Nigeria. These are the first cases ever diagnosed in the UK, and they were picked up very quickly based on the clinical presentation.
 
Monkeypox has been becoming more common in Africa since 2005 when smallpox vaccination stopped. From 2005 to 2007 the incidence increased 20 fold. This is because the smallpox vaccine also protects against monkeypox. As immunity to smallpox wanes so does immunity to monkeypox.
 
How does monkeypox present?
Most cases of monkeypox are mild and self-limiting. However it can be virtually impossible to distinguish smallpox and monkeypox clinically when severe infection of either occurs; they are very similar viruses and have similar presentations. The main difference is that in monkeypox lymphadenopathy is much more pronounced. Also if you see a case of “smallpox” in the era of smallpox eradication it is likely to be something else i.e. monkeypox.
monkeypox virus
Click for larger image
Patients tend to present 5-21 days after exposure with a severe flu-like illness: high fevers (40oC), headache, malaise, backache and vomiting. It can easily be mistaken for almost any viral illness! The rash starts to appear 2-4 days after the prodromal illness and spreads from the hands and feet to the face and finally to the thorax. The skin lesions are initially macular (flat and red), becoming vesicular (small blisters) before finally appearing as pustules (pus filled blister). The pustules eventually scab over and fall off. Skin lesions are consistently similar but the time they present alters their appearance e.g. all the older skin lesions on the hands would look the same (pustular) but any newer lesions which later appear on the thorax would look more immature than those on the hands, yet these thoracic lesions will all look the same (macular).
 
How is monkeypox diagnosed?
If a patient in the UK is suspected of having monkeypox then they should be discussed urgently with the Imported Fever Service at Porton Down as well as Public Health England. Samples (e.g. fluid or viral swabs) should be taken from the skin lesions for PCR and serum should be taken for antibody testing. The IgM antibody can normally be detected within 5 days of illness and the IgG by day 8. PCR will be positive from the skin lesions throughout the illness. Porton Down will give further advice on taking and transporting samples, don’t just send them to your local laboratory… they will not be happy.
 
Can monkeypox be treated?
The mainstay of treatment of monkeypox is supportive care. The drug Cidofovir has been tried in the treatment of monkeypox, and has been shown to have activity in animal studies, but given the rarity of the infection there is no definitive evidence of its efficacy. In my experience Cidofovir is nasty stuff and most patients I have used it in have gone into renal failure and had problems with bone marrow suppression therefore its use may be more harmful than the infection itself!
 
Infection control
Human-to-human transmission of monkeypox is uncommon although it can occur. Contact with infected body fluids is required for transmission to occur. Secondary cases can occur but further transmission is uncommon. The secondary attack rate amongst close contacts in remote villages in Africa is 8% but it may well be less in other environments e.g. healthcare where PPE is used.
 
The cases identified in the UK have been transferred to specialist infectious diseases units but this is probably not essential. Infection control precautions should continue until all of the skin lesions have healed, usually about 14-21 days after they appear. The most important infection control and public health measures are:
Public Health
Notify Consultant in Communicable Disease Control for Public Health England
Isolation
  • If patient already admitted, transfer to or keep in a single occupancy room with own toilet facility
  • Door to be kept closed
  • If available use a negative pressure room
Hand Hygiene
Soap and water or alcohol hand gel
PPE
  • Use gloves, plastic aprons, fluid repellent surgical face mask and visor AT ALL TIMES
  • PLUS FFP3 respirator face masks for aerosol-generating  procedures*
  • Remove ALL PPE before leaving room
Laboratory tests
  • No specimens should be sent to the laboratory without prior discussion with the Microbiologist
  • Minimum tests can be carried out at containment level 2 in closed analysers or in containment level 3 for open tests e.g. malaria screen
Staff
  • Restrict the number of staff who have contact with patient to essential staff only
  • Compile a list of all staff in contact with the case, which should be retained by Occupational Health Department
Environmental decontamination
  • Deep clean clinical area daily by nursing staff caring for patient and after patient is discharged
  • All waste to be treated as infected and disposed of by incineration
​*Aerosol-generating procedures include:
  • Endotracheal intubation
  • Bronchoscopy
  • Airway suctioning
  • Positive pressure ventilation via a face mask
  • High frequency oscillatory ventilation
  • Central line insertion
  • Diagnostic sputum induction
 
Prognosis
In Africa the mortality from monkeypox is approximately 10%, especially in children. However during the outbreak in the USA no one died which suggests that mortality may be multifactorial including access to healthcare and nutritional status. This is in contrast to variola major, the most severe form of smallpox, where the mortality was 20-50%!
 
So let’s hope that the two patients so far identified in the UK get better quickly and that there are no further cases. In the meantime we all need to be extra vigilant and keep an eye out for odd rashes…and gigantic rats!

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    Blog Author:

    David Garner
    Consultant Microbiologist
    Surrey, UK

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