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Sunday, Oct 02, 2022

Explained: Why monkeypox is spreading, but not as fast as Covid-19

There have been 14,533 probable and laboratory-confirmed monkeypox cases reported from 72 countries this year until July 20, according to the WHO, increasing from 3,040 cases across 47 countries recorded in the beginning of May.

Explained Health, Express Explained, Express exclusive, Monkeypox, Explained, Indian Express Explained, Opinion, Current AffairsInternational passengers being screened at Chennai airport after the first case was detected in neighbouring Kerala last week. PTI

The detection of monkeypox on Sunday in a 34-year-old Delhi resident, who had no history of international travel, marks India’s first case of local human-to-human transmission. This comes a day after the World Health Organization declared the outbreak a public health emergency of international concern (PHEIC), its highest level of alarm.

What does declaration as a PHEIC mean?

A PHEC is declared for “an extraordinary event which is determined to constitute a public health risk to other States through the international spread of disease and to potentially require a coordinated international response”.

The declaration for monkeypox came amid growing cases worldwide, with the viral infection spreading to regions where monkeypox had never been detected before. There have been 14,533 probable and laboratory-confirmed monkeypox cases reported from 72 countries this year until July 20, according to the WHO, increasing from 3,040 cases across 47 countries recorded in the beginning of May.

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Deaths have been low at five — three from Nigeria and two from the Central African Republic, countries where the disease was already known to occur before this outbreak.

Where has monkeypox occurred before?

Monkeypox is not a new disease like Covid-19, which emerged in 2019. The first monkeypox infection in a was identified human in 1970 in the Democratic Republic of Congo in a nine-month-old boy. Most infections initially were caused by interaction of humans and animals in rural, rainforest regions of the Congo basin. Before the 2022 outbreak, rising cases was being reported from Central and West Africa. The first outbreak outside Africa happened in 2003, when the United States saw over 70 cases.

What do we know about the disease?

Monkeypox is a self-limiting viral infection, with symptoms lasting 2–4 weeks. The case fatality ratio ranges between 0 and 11%.

The most common symptoms include fever, headache, muscle ache, back pain, low energy, and swollen lymph nodes, along with rashes that last for 2–3 weeks. Although mostly mild, it can lead to complications and deaths in children and those with a weak immune system. Complications include pneumonia, secondary skin infections, sepsis, encephalitis, and infection in the cornea leading to blindness.

Can vaccines work against it?

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The monkeypox virus belongs to the same family of orthopoxviruses as smallpox, now eradicated. Orthopoxviruses are cross-reactive, meaning that existing smallpox vaccines and therapeutics can be used for monkeypox.

Although most monkeypox cases are treated symptomatically, an antiviral agent known as tecovirimat developed for smallpox may be used. The US, which has recorded over 2,800 cases, is using two vaccines meant for smallpox. Jynneos with two doses is allowed for use in adults, while ACAM2000 uses a live, attenuated form of a different orthopoxvirus and is meant for protection of high-risk individuals for smallpox such as lab workers.

“Vaccination against smallpox was demonstrated through several observational studies to be about 85% effective in preventing monkeypox. Thus, prior smallpox vaccination may result in milder illness,” according to the WHO.

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The mass vaccination campaign against smallpox had ceased in 1980. “Most of those who are in their 40s must have received the smallpox vaccine at birth and might be at a lower risk of getting infection. Most cases occurring in people below that age group supports the hypothesis,” said Dr Ekta Gupta, professor of virology at the Institute of Liver and Biliary Diseases.

All four cases reported in India are in people in their early to mid-30s.

Why is there a surge now?

From animals to humans, the infection is known to get transmitted through direct contact with blood, bodily fluid, or lesions in the infected animals. Human-to-human transmission can happen either through large respiratory secretion or contact with lesions of the infected person or contaminated objects.

However, unlike with say influenza or Covid-19, transmission of monkeypox through respiratory droplets needs prolonged face-to-face contact. That usually happens only in the case of families and healthcare workers.

“It is not as transmissible as Covid-19, so it is unlikely to lead to an outbreak like that as well. However, the recent spread could be linked to declining herd immunity from smallpox vaccination. It was always expected that the vaccine immunity will go down, but we did not anticipate that the animal strain would take over,” said Dr Gupta.

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She stressed a need to investigate whether the Covid pandemic might have impacted the immune system in a way that may have made people more susceptible to other infections.

Over the years, the transmission chain — the number of successive person-to-person infections – has increased from six to nine. Dr Rosamund Lewis, the WHO’s lead expert on monkeypox, has called for research to see whether there was a change in the virus, or whether this was happening because of the declining number of people immunised against smallpox.

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Is monkeypox sexually transmitted?

Although the WHO says it is unclear if the infection is transmitted sexually, it is under investigation with almost all cases in the current outbreak being reported in gay or bisexual men. A recent analysis of 528 persons from London, published in the New England Journal of Medicine,  shows 98% of those infected were gay or bisexual men and suggests transmission in 95% cases happened through sexual activity. In 29 of 32 persons whose semen was analysed, monkeypox DNA was found.

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“It is unclear whether it is sexually transmitted, but the infection might be transmitted more while having sex due to increased skin contact and many people with the infection reporting lesions in the genital regions,” said Dr Gupta.

First published on: 25-07-2022 at 04:24:31 am
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