A rise in the number of people testing positive for mpox has sent alarm bells ringing globally. Apart from the Democratic Republic of Congo (DRC), which has the highest spread of mpox, the virus has also spread to 13 African countries. Two countries outside of Africa—Sweden and neighbouring Pakistan—have also reported their first cases of mpox.

Last week, the World health Organization declared the outbreak a public health emergency of international concern (PHEIC).

The disease is caused by the monkeypox virus, which is believed to originate from wild animals, and causes flu-like symptoms, muscle aches and a rash with pus-filled lesions all over the body. It can range from mild to fatal and is more common among children than adults.

Under WHO’s International health regulations, a PHEIC is “an extraordinary event” that is an immediate public health risk to all countries owing to the international spread of disease and requires “a coordinated international response”.

But this is not the first time you may have heard of mpox. Neither the outbreak nor the disease is entirely new. It is endemic to countries in central and west Africa and the DRC has been reporting mpox cases for over a decade.

So, what prompted the alarm? And how exactly did this virus come about?

Why the alarm? This is the second time the WHO has declared it a PHEIC. The mpox virus was first detected in humans in 1970 and has been around ever since.

The WHO had first declared it a PHEIC in July 2022, when the multi-country outbreak began spreading rapidly. The global health body, in May 2023, said the emergency was over after a noticeable decline in global cases.

However, cases began rising again since September last year. And, alarmingly, the number of reported cases in the 8 months of the current year—over 15,000—have exceeded last year’s total. This year alone, mpox has claimed over 500 lives.

So, what’s different this time around? The current outbreak is linked to a relatively new strain of the virus, known as clade 1b—an offshoot of clade 1. Remember that different clades, or descendants, of the mpox virus carry varying levels of risk and are transmitted in different ways. The 2022 outbreak was caused by a different strain called clade 2.

According to Sweden’s public health agency, clade 1 strains are more virulent, severe and bear a greater risk of mortality.

The Washington Post’s report says that clade 1 infections strike more vulnerable people; this includes children and those in areas where healthcare is less accessible.

However, the spread of clade 1b in areas or countries that have previously not reported cases of it largely appear to be sexually transmitted—between homosexual and heterosexual partners.

This is worrisome because concerns over societal judgment and stigma and fear over legal recourse—in places where homosexuality is illegal—could prevent those affected patients from getting treated.

“The current upsurge of mpox in parts of Africa, along with the spread of a new sexually transmissible strain of the monkeypox virus, is an emergency, not only for Africa, but for the entire globe,” said IHR Emergency Committee chair professor Dimie Ogoina.

So, how risky is it for Indians? While the health ministry has said there is no cause for alarm yet, it has begun checking at international airports and seaports over the possibility of some “imported cases”.

“Although the possibility of a few imported cases being detected in the coming weeks is not entirely ruled out, it was assessed that the risk of a large outbreak with sustained transmission is presently low for India,” a ministry statement said on Saturday after a review meeting of health officials.

During the 2022 outbreak, India reported about 27 cases of the mpox virus. This was the clade 2 type and mostly among those with a history of international travel.

After the COVID-19 pandemic, which brought the world to a standstill and changed the way health emergencies are perceived, fears over mpox spreading similarly have intensified. But there’s lesser chances of mpox snowballing to that extent owing to the difference in the nature of this virus and the fact that there are vaccines in place, albeit in limited supply.

What is mpox? Mpox is caused by the monkeypox virus or MPXV—an enveloped double-stranded DNA virus, which belongs to one offshoot of the Poxviridae family of viruses called Orthopoxvirus. In that way, it is similar in structure and nature to smallpox and cowpox. This is why it is believed that vaccines designed to fight smallpox can help treat mpox infections and ease its symptoms, since the two diseases are genetically similar.

Note that there has been no vaccine specifically designed for mpox, but the WHO recommends using the MVA-BN, LC16, or the ACAM2000 vaccines to treat mpox. The MVA-BN, short for Modified Vaccinia Ankara by Bavarian Nordic, is a non-replicating two-dose smallpox vaccine marketed as Jynneos in the US and Switzerland and as Imvamune and Imvanex in Canada, EU and the United Kingdom. LC16 is a freeze-dried smallpox vaccine manufactured by Japan’s KM Biologics and is the only one approved for use among children. The ACAM2000 is a second-generation vaccine that contains a live vaccinia virus and is manufactured by US-based Emergent Bio Solutions. While it has been designed for prevention of smallpox, it is being considered for use against mpox.

However, this vaccine stockpile is largely limited in volume and health experts fear that it is still not reaching the most vulnerable in African countries. These vaccines also remain unavailable in India, where smallpox was eradicated in 1979. In other countries too, supply is largely limited. Note that the WHO has not recommended mass vaccination against the zoonotic virus yet.

Interestingly, mpox was previously referred to as monkeypox owing to the first documented cases of the disease in captive monkeys in 1958. However, as medical researcher Rodney E. Rohde writes in The Conversation, there isn’t enough evidence to claim that the virus jumps from monkeys to humans or that monkeys are major carriers of the disease.

So, how does it spread? The WHO says that animal to human transmission can be through bites, scratches, hunting, playing with carcasses of or eating infected animals. However, the exact extent of viral circulation in animals is not known. Much of the present spread, internationally, is primarily through human contact.

Among humans, the disease primarily spreads through close contact, including talking or breathing in close quarters, sex and through skin-to-skin contact. Typically, the mpox virus enters through open cuts, inhalation or mucous membranes in the eyes, nose or mouth. It is believed that transmission is mostly through inhalation of large respiratory droplets than indirect contact such as clothing, sharing the same bed or touching the same surfaces. Unlike the coronavirus, there is little evidence to believe it remains on surfaces.

Mpox symptoms can take anywhere between one week to 21 days to appear after exposure to the infection. And, it can be difficult to diagnose as it shares common symptoms with chickenpox, measles, bacterial skin infections, scabies, herpes and syphilis.

Cover image from Wikimedia Commons