At least two countries outside of Africa have reported mpox cases after the World Health Organization (WHO) declared that the virus had become a “public health emergency” earlier this week.

A relatively new strain of the virus known as clade 1 has been spreading in African countries since 2022.

Earlier this year, it was reported that the Democratic Republic of Congo (DRC) was experiencing the biggest outbreak of the disease ever recorded, with tens of thousands of people infected as of June. The government of DRC had declared it an epidemic in December 2022.

Last week, the Africa CDC reported that mpox has now been detected in at least 13 African countries. Compared with the same period last year, the agency said cases are up 160 percent and deaths have increased by 19 percent.

Here is what we know so far about where the disease has spread, how it affects the human body and how to protect yourself from infection.

To which other countries has the new strain of mpox virus spread?

The Pakistan Ministry of National Health Services confirmed its first case of the virus on Friday, saying the person had come from Saudi Arabia.

Health officials said sequencing is underway to determine the exact strain of the virus the person had been infected with.

On Thursday, Swedish health officials reported the country’s first case of mpox, confirming that it was the clade 1 strain, and said the person had become infected in Africa and is now receiving treatment.

Clade 1 tends to cause a higher number of severe infections and appears to be more easily spread through routine close contact, including sexual contact.

On Friday, the European Center for Disease Prevention and Control (CDC) raised its risk alert level to “moderate” from “low” and asked countries to maintain high levels of awareness among travellers visiting from affected areas.

How does the virus attack the human body?

Mpox mainly affects humans and animals. It belongs to the same family of viruses as smallpox but causes milder symptoms, such as fever, chills, and body aches. It can cause severe illness, and even death in some cases, however.

The virus enters the human body through broken skin or via the airways. It then spreads through the blood causing a person to experience flu-like symptoms and develop lesions on the skin.

According to Michael Marks at the London School of Hygiene and Tropical Medicine, scientists “don’t think that mpox has direct effects on the immune system”.

“Beyond the fact that all infections obviously transiently cause responses in the immune system, we don’t believe there are long-term impacts on the immune system from mpox,” he said.

Dr Ngashi Ngongo, chief of staff at Africa CDC, also told Al Jazeera that the virus only causes symptoms that last “two to four weeks”.

“It’s a disease. Whether you get the severe form – then it leads to death – or you just recover [in] two to four weeks. Everything goes back to normal,” he said.

How does the virus spread?

The virus is spread by close contact with an infected person or animal. For human-to-human infection, the virus can be passed on through contact with skin lesions, skin-to-skin contact, and talking or breathing too close to an infected person.

It can also be spread via contaminated objects such as surfaces, bedding, clothing and towels, as the virus enters the body through broken skin, the respiratory tract, or the eyes, nose, and mouth.

Marks told Al Jazeera that the most important form of transmission is through skin-to-skin contact as the virus remains detectable on skin lesions for “three weeks or so”, rather than via the respiratory system since in “most people the virus is cleared from the throat by seven to 10 days”.

For human-to-animal transmission, the virus typically enters the body through bites, scratches or contact with the wounds on an infected animal.

What are the symptoms?

The disease causes flu-like symptoms and pus-filled lesions. It is usually mild but can be severe enough to kill.

Marks explained that most people have a “relatively mild illness” where they could have a fever, muscle aches and a rash with “five to 25 lesions”.

“Some people become much more unwell and they may develop a more severe illness with hundreds of lesions all over the body,” he said.

What variables can cause more severe symptoms?

While Marks explained that the illness presents mild symptoms in most people, some people are at higher risk of experiencing severe symptoms.

“For example, people with untreated HIV [a sexually transmitted illness] or a weak immune system are at still higher risk of severe disease. Children also seem to be at higher risk of severe disease,” he said.

Children, he explained, are likely affected by mpox more than adults for “several reasons”.

“A lot of the transmission is in densely populated areas with many children, and children are probably more prone to running around and coming into direct skin-to-skin contact with others – so that then causes transmission. Whereas adults have less direct contact with others,” he said.

Ngongo added that children are also at higher risk as their “defence mechanism” – the immune system – is still developing.

What treatment is available for this strain of mpox?

There is no current treatment for mpox but some antiviral drugs are being tested, Marks said.

“There is, however, vaccination, which is effective at reducing risk. The priority needs to be getting an adequate supply of vaccine to those populations most at risk in DRC and surrounding countries,” he said.

“If we can vaccinate individuals at risk they will be protected from infection and this will help control the epidemic – so both benefit the person vaccinated and the broader population,” he added.

A vaccine for mpox, which was used in the 2022 outbreak by many Western countries, is not accessible by poorer African nations, Ngongo explained.

“There is no vaccine in Africa. Whatever is left of that vaccine is stockpiled in the West as part of their own emergency preparedness. But we have an ongoing emergency here,” he said.

Ngongo explained that through donations, Africa CDC has managed to obtain 280,000 doses. However, for the vaccine to be effective, people must take two doses, lowering the amount they have for 140,000 people only.

How can you protect yourself?

Ngongo advised people to “go back to the basics of personal hygiene” and remember to wash hands, avoid contact with those who are sick and advise people to go to the hospital if they are displaying symptoms so that the virus can be contained.

Mpox vaccines are also effective in protecting the population if you are in a country where it is accessible.

Could the mpox virus spread further?

Given the resources in richer countries to stop the spread of the virus, scientists believe that if new outbreaks linked to Congo are identified quickly, transmissions could be stopped relatively quickly.

The “major risk”, Marks said, is in central Africa where the epidemic is occurring and spreading.

“There are likely to be small numbers of cases exported further afield, as [in] the Swedish case, but the major risk and the focus for action needs to be on central Africa,” he said.

Ngongo also urged people to learn from the COVID-19 pandemic and “act now”.