The world is now facing an international epidemic of monkeypox for the first time ever. Nearly 800 cases have been identified by doctors from all over the world, including in Argentina and the United Arab Emirates. Portugal and the United Kingdom have the highest number of cases with approximately 200 and 100, respectively. The United States has 21 cases, while Canada has 58.

This broad geographical spread indicates that “widespread human to-human transmission is currently underway,” Dr. Maria van Kerkhove from the World Health Organization said on Thursday. She noted that this transmission “likely has been ongoing for several days, if not months.”

Two studies published Thursday show that the virus is spreading undetected in certain communities in Portugal and the U.K. aEUR,” because the majority of cases are not connected to one another or to a common activity or place. Scientists conclude that health officials are not able to determine where the virus is spreading and that many cases are not being diagnosed.

Officials in the United States don’t know the location of one case that caught monkeypox. “There may be community-level transmission. “That’s why it’s important that we really increase our surveillance efforts,” Jennifer McQuiston (Deputy Director of the Division of High Consequence Pathogens and Pathology, Centers for Disease Control and Prevention) said Friday. “I want you to know that this could also be happening in other areas of the United States.

This may be due to the fact that symptoms of monkeypox can be more subtle in this case than in previous cases.

Health officials have asked health care workers and anyone who may have been exposed to monkeypox to keep an eye out for signs, particularly rash, related to the disease.

What does a rash look like? According to Donald Vinh, a McGill University infectious disease doctor, this rash is not as common as medical textbooks suggest. These images show people with pus-filled blisters on their hands and trunks. Vinh and other experts involved in the outbreak believe that there may be more to this outbreak than meets the eye.

Some patients may only have one or two small lesions, which can be easily confused with lesions from several sexually transmitted diseases like syphilis and herpes.

Vinh believes that Vinh is being too critical. “Because it’s easy to overlook these patients,” Vinh said. They are still contagious, and could spread the disease.

Vinh helped to treat five people with monkeypox at McGill University Health Centre, Montreal. He estimates that there are at least 50 cases in the city.

A colleague called Thursday morning to talk about a patient who was newly diagnosed with monkeypox. The patient had one lesion.

He said that the patient’s skin lesions, which he tested to confirm his diagnosis, were extremely subtle. He says it’s not what you see on Google images of monkeypox.

Monkeypox, as it is often described in textbooks and on agency websites, begins with flu-like symptoms. These include a fever, fatigue, and one swollen lymph gland. A rash develops on the skin, first on the forehead and then on the extremities about a week later. The rash can cause painful blisters and eventually crust with pus. It can eventually cover the trunk and entire body.

Vinh explains, “So in the classic monkeypox described in textbooks you’re supposed have two phases.”

Vinh and other doctors who have been involved in the current outbreak say that many people’s symptoms do not fit this profile.

The rash is often not on the skin or the extremities. It usually begins in the genitals and the anus. Sometimes it spreads to other parts of your body.

Vinh states, “You don’t have head to toe skin pox lesion,” It’s more localized to one area of the body like the genital areas. Some people only have one or two pox. It’s not common.”

He said, “Sometimes it isn’t even a pox,” but rather an ulcer or the crater.

Monkeypox can affect any part of the body, even if it’s only a small area. Jennifer McQuiston, CDC, says that the rash can be very painful and some patients may need prescription pain medication to manage it. “The skin can become scarred over time from the sores.”

What about flu-like symptoms? Vinh and other doctors discovered that they sometimes don’t show up at all. They can also appear after skin lesions have appeared. Patients may have one swollen or multiple lymph nodes. JAMA was told by Agam Rao, an infectious disease specialist with the CDC.

One Montreal clinic saw a monkeypox patient who had one small lesion on his penis. It was not painful. On Twitter, Dr. Sebastien Poulin, from the Clinique l’Agora explained that he had never experienced fever.

He wrote, “The bottom line of the tweet will be: AWe must have an high index of suspicion for ‘atypical’ MonkeyPox casesA>>.”

Because of the wide range of symptoms, U.K. health officials are looking to find new cases. They ask people to keep an eye out for any kind of rash.

The agency said Tuesday that while the risk to the UK population is low, it asked people to be aware of any new lesions or rashes, which could appear as spots, ulcers, or blisters on any part.

“While this advice is applicable to all, most cases have been identified in men who are gay, bisexual, or who have had sex with men. We are asking them to be aware, especially if they recently had a new partner.

Monkeypox is spread primarily by close contact with infected persons, such as contact with the rash and skin lesions. Mateo Prochazka, an epidemiologist, explained that this contact can happen during sex. Prochazka is a consultant for the U.K. Health Security Agency. He identifies himself as a gay man.

He said that the risk of each person contracting the virus is greater because of how they interact during sex. Usually, it’s skin to skin for a time. This means that gay men, particularly gay men with extensive sexual networks, may be experiencing an increase in cases due to their potential behavior and how many contacts they have.

He said, “So it’s not about sexual identity but more about sexual networks.”

While surveillance has been limited to men who have had sex with women, Dr. Maria van Kerkhove, WHO, stated that countries are expanding their search. “We need to say that so far surveillance has been biased towards [men who sex with women] at the moment. We are now working with countries to expand that surveillance beyond clinics, ID clinics and emergency departments.”