Monkeypox: why the sudden concern?

The media have been full of headlines about a tiny number of cases of the viral disease monkeypox.  What do we know about it, why has there been a recent surge and, given the experience with Covid-19, should we be getting concerned?

What is monkeypox infection like?

  • Monkeypox is a viral infection that causes flu-like symptoms
  • It also causes swelling of the lymph nodes
  • It has a characteristic blistering rash especially on the hands, feet and face
  • Most people recover within 2 weeks

Is there more than one kind of monkeypox?

  • Like Covid-19, there is more than one genetic strain
  • There appear to be 2 major strains, one predominant in Western Africa in countries such as Ghana and Nigeria, and the other in Central Africa in countries like Democratic Republic of Congo
  • The Western Africa strain has a very low mortality – even in poor rural populations – of around 1%, whereas mortality is much higher – 10% – from the Central Africa strain
  • Fortunately the strain identified as causing cases in Europe and America is the milder West African strain

Why have public health experts got excited recently?

  • Basically up to the last week or so, cases of monkeypox were only seen in Africans or in people from Africa who had spread the infection elsewhere
  • The recent concern is that the new cases in Europe, Australia and North America do not seem to have had any African contact 
  • Obviously, the number is growing but around 200 cases have now been diagnosed in the past week outside Africa which is more than the entire total of non-African cases diagnosed since 1970
  • Why this should be so is unknown

How does monkeypox spread? 

  • Monkeypox spreads differently from Covid-19 
  • Basically it requires much closer contact 
  • Also – unlike Covid-19 –  asymptomatic spread, ie catching the disease from someone without symptoms at the time of contact, is (or was) very unusual

Anything unusual about the new cases in Europe?

  • As mentioned above, the lack of contact with an affected African individual is very unusual 
  • Secondly, and at this stage only based on individual reports, there does appear to be asymptomatic spread, which could be worrying
  • Thirdly, the recent cases have been proportionately greater in gay and bisexual men aged 30-50
  • Whether this suggests that it is transmitted by sexual intercourse is unknown, but monkeypox had not been thought to be a sexually transmitted infection

What do we know about the monkeypox virus?

  • Monkeypox virus is much larger than the Covid-19 virus 
  • Its genome is DNA rather than RNA (like Covid-19) and this is important as DNA viruses are more resistant to mutations, so for example it is much less likely than Covid-19 to mutate into more transmissible forms (like Omicron)
  • The genome of the virus was sequenced last week (in Portugal) and we still need to see if there are any mutations that might evolve as new cases emerge

What about the connection with smallpox?

  • This is probably the good news bit!
  • Smallpox and monkeypox viruses are closely related
  • Smallpox was only transmissible from person to person and hence a widespread international vaccination campaign led to the complete eradication of smallpox
  • The last case of smallpox in the world was in Somalia in 1977
  • Thus for decades there have been no new cases of smallpox and there is no need for anyone now to be vaccinated it
  • Studies from Africa show that smallpox vaccine provides 85% protection against monkeypox which is good news for older generations who have received this vaccine
  • Interestingly smallpox vaccines are used as a treatment for new cases of monkeypox, as well as for protecting close contacts
  • There are also specific monkeypox vaccines that have been developed for use in Africa, which seem to be very effective with low risk of side effects

The outstanding questions:

  • If this virus is now spreading from asymptomatic cases, that will make quarantining and containing spread more difficult.
  • Whilst older people will have been vaccinated against smallpox, and hopefully protected against monkeypox, if any kind of outbreak takes hold it could it spread quite quickly amongst generations who were not vaccinated 
  • Remember it is a mild disease, but I’m not sure that any country would wish to see an outbreak, or any individual developing an infection, even with ‘only’ a 1-2 week duration of being unwell, given what we have all gone through with Covid-19!

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