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monkeypox / mpox (MPVX)

see also:

  • In Victoria, monkeypox is an urgent notifiable condition, in accordance with Victorian statutory requirements.


  • a member of the poxviridae virus family (as with smallpox (SPX)) and immune responses to this family of DNA viruses generally demonstrate cross-reactivity across the various viruses
  • Whenever there are multiple viruses targeting the same host at the same time, it is the virus with the greater R0 (basic reproduction number) that usually establishes infection. SPX had the greater R0 until its eradication; therefore, no MPVX cases were heard until 1980. With the eradication of SPX in 1980, we became susceptible to MPVX infection, and it was around that time that H- MPVX cases started appearing.
    • in 1970, population immunity to smallpox was 66%, dropping to 2-10% by 2016 due to cessation of vaccination
  • 1st discovered in 1958 in colonies of monkeys
  • 1st reported in human populations in the African country, Democratic Republic of the Congo, in 1970
  • has been endemic in some African countries including Nigeria, Liberia, Sierra Leone and the Democratic Republic of the Congo for many years
    • cases occur sporadically and outbreaks are usually contained and quickly burn out
    • in Congo 1980-85, 90% of infected were aged under 15yrs, mortality rate amongst unvaccinated was 11%, higher in young children
    • a large outbreak again occurred in Congo in 1996-97 with 511 confirmed cases
    • in 2020, 4,594 suspected cases were reported from the DRC
  • a rare infection in humans and usually resulting from very close intimate contact with infected humans or from contact with or bites from infected wild animals (esp. rats, squirrels and monkeys) in areas where monkeypox is endemic such as western and central Africa
  • Monkeypox has sickened people for decades in central and west Africa, where one version of the disease kills up to 10 per cent of people infected.
  • Two separate clades of MPVX have been identified:
    • Congo Basin (more virulent and infective) and West Africa.
    • The case fatality ratio (CFR) for the Central African clade was higher than that of the West African clade.

2022 epidemic

  • some superspreading events associated with air travel, international gatherings and multiple-partner sexual encounters contributed to early spread
  • spread has been far more widespread as this strain is often causing minimal lesions (often only one oral or rectal papule) and minimal or no fever/headache or even asymptomatic cases allowing infections to go unnoticed for longer
  • The number of cases reported in the first week of this outbreak has surpassed the total number of cases in Western and Central Africa in the last 40 years.
  • unlike previous outbreaks, in this outbreak, most cases have occurred through human-to-human transmission and in people with high-risk behaviors and MSM
  • the outbreak is milder, with hardly any fatalities, most likely because of the West African clade, and the rash has a different pattern due to the outbreak mainly being sexually transmitted resulting in 75% having genital lesions.
  • There had been almost 1,500 suspected cases of monkeypox in the 1st few months of 2022 in Central Africa and 70 deaths
  • in May 2022, there was a small outbreak of the less fatal strain (usually having 1% mortality) in western Europe amongst men - Portugal, UK
  • by end of June 2022, there were more than 3,200 confirmed monkeypox cases and one reported death, affecting 48 countries, and there were 5 unrelated cases in Victoria.
  • by end of July 2022, WHO declared it a global emergency as cases reach over 16,000 cases in 75 countries and 5 deaths since June (deaths have only been in Africa where a more severe strain is endemic - mainly Nigeria and Congo)
    • thus far, 99 per cent of all the monkeypox cases beyond Africa have been men, and of those, 98 per cent have involved men who have sex with men, and most are aged 18-44yrs
  • by early August, 25,000 cases reported globally
  • by 20th Aug 2022, 40 cases have been confirmed in Victoria - half acquired locally and are mainly in Melbourne.
  • by mid Oct 2022, the CDC documented 72,547 cases in 109 locations and a total of 26 deaths have been reported from 12 locations.

Clinical features

  • fever and chills
  • myalgias
  • fatigue
  • pox-like rash esp. face, genitals, hands soon after infection and these may last for several weeks and be infectious until fully healed
  • lesions may also appear inside the mouth, eyes and other parts of the body that produce mucus
  • lymphadenopathy (this is unlike smallpox which does not cause enlarged LNs)
  • may cause acute myocarditis


  • most people (who are not pregnant) have mild disease with recovery within a few weeks
  • may cause miscarriage or 2nd trimester stillbirth
  • mortality is likely higher in vulnerable groups such as newborn babies and pregnant or breastfeeding women
  • the Nigerian cases have had a fatality rate of 3%


  • smallpox vaccines are about 85 per cent effective in preventing monkeypox
    • a live-attenuated smallpox vaccine called ACAM2000 / Jynneos is available in Australia and can be used before or after exposure
    • has been linked to “rare but serious adverse events”
    • is not suitable for severely immunocompromised people
  • cover skin lesions
  • wear a mask in shared spaces
  • decontaminate surfaces, bed linen, clothes, towels
  • avoid mucosal or skin contacts with those who are infected
  • consider caesarian section if vaginal lesions at time of birth


  • virus can enter the body via placenta, broken skin, the respiratory tract or mucous membranes
  • spreads through direct contact with respiratory secretions, such as mucus or saliva, fomites or skin lesions such that the exchange of mucosal fluids or direct contact with the virus ion contaminated surfaces s in sufficient quantity to seed an infection.
    • whilst viral DNA has also been found in faeces, semen, blood and urine it is not yet clear if these transmit infection
    • the potential airborne and respiratory droplet spread is also being investigated - perhaps co-existent Covid-19 induced coughing may be contributing to the transmission although this may or may not give sufficient viral loads
  • anyone who has prolonged, close contact (not necessarily sexual, may include kissing or cuddling) with an infected person is at risk, including partners, parents, children or siblings, among others.
  • the most common settings for transmission are within households or health care settings.
  • the 2020 epidemic primarily spread via intimate contact amongst men who have sex with men
  • contact with or bites from infected wild animals (esp. rats, squirrels and monkeys)
  • pregnant women can transmit to babies via placenta or after birth from close contact
  • a case has been reported in 2022 of transmission from men to their pet greyhound dog
monkeypox.txt · Last modified: 2022/11/29 04:42 by wh

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