The World Health Organization (WHO) issued its highest alert level for the global monkeypox outbreak, now designating the virus as a public health emergency of international concern.

This alert means the global health authority views the outbreak as significant enough to garner a coordinated international response to prevent the virus from escalating to dangerous and potentially difficult to contain levels.

More than 18,000 cases of monkeypox has been confirmed in more than 78 nations, according to WHO data, increasing by 77% from last June through early July. About 10% of monkeypox patients have been hospitalized to manage pain from the disease.

"We have an outbreak that has spread around the world rapidly, through new modes of transmission, about which we understand too little," WHO Director General Tedros Adhanom Ghebreyesus said. "For all of these reasons, I have decided that the global monkeypox outbreaks represents a public health emergency of international concern."

The WHO can only issue guidance and recommendations to member states, not mandates, so this designation is more of a call to action to national governments.

The global monkeypox outbreak is unusual since it is spreading in parts of the world where the virus is not typically found. Since its discovery in humans in the 1970s, monkeypox has spread at low levels in West and Central Africa. Now, the virus appears to be more efficient at human-to-human transmission in ways that scientists are still trying to figure out.

Health experts believe monkeypox is spreading through intimate, skin-to-skin contact, with men who have sex with men being the main group affected at this time. However, the disease is not considered to be sexually transmitted, meaning it can spread through other forms of close contact.

Europe is currently the global epicenter of the outbreak, reporting more than 80% of confirmed cases so far this year. Tedros said the risk posed by monkeypox on public health is moderate globally, but high in Europe.

The United States has reported more than 3,500 cases of monkeypox across 46 states, Washington D.C. and Puerto Rico, according to the U.S. Centers for Disease Control and Prevention (CDC). Most people recover from infection in two to four weeks, the CDC said, with the virus causing an often painful rash throughout the body.

Five deaths have been reported in Africa this year, according to the WHO, with no death occurring outside of Africa so far.