For a world tired of fighting coronavirus, the monkeypox outbreak raises a key question: Am I at risk?
The answer is reassuring. Most children and adults with healthy immune systems are prone to dodging serious illnesses, experts said in interviews. But there are two high-risk groups.
One includes babies under six months. But they are not yet affected by the current outbreak. And many older adults, the group most likely to succumb to the monkeypox virus, are at least somewhat protected from decades of smallpox vaccines, studies suggest.
Vaccinated older adults can become infected, but are likely to escape with only mild symptoms.
“The end result is that even those who were vaccinated many decades ago maintain a very, very high level of antibodies and the ability to neutralize the virus,” said Dr. Luigi Ferrucci, scientific director of the National Institute. of Aging.
“Even if they were vaccinated 50 years ago, that protection should still exist,” he said.
In the United States, routine smallpox immunization ceased in 1972. The military continued its vaccination program until 1991 as a precaution against a bioterrorism attack.
Questions about the durability of the smallpox vaccine increased after an anthrax attack in 2001, said Dr. Anthony S. Fauci, chief adviser to the Biden administration on infectious diseases. He said it was reasonable to assume that most vaccinated people were still protected, “but the durability of protection varies from person to person.”
“We can’t guarantee that a person who was vaccinated against smallpox is still protected from smallpox,” Dr. Fauci said.
The smallpox outbreak has grown to include about 260 confirmed cases and more scores under investigation in 21 countries.
In the United States, the Centers for Disease Control and Prevention tracks nine cases in seven states, not all of which have a history of travel to countries where monkeypox is endemic. This suggests that there may already be some level of community transmission, Dr. Rochelle Walensky, the agency’s director, told reporters on Thursday.
Dr. Walensky said 74 labs in 46 states have access to a test that can detect monkeypox, and together they can examine up to 7,000 samples a week. The agency is working to expand that capacity, he said, adding, “We’ve been preparing for this type of outbreak for decades.”
Monkeypox infection begins with respiratory symptoms, but turns into a different rash, first in the mouth, then in the palms of the hands and soles of the feet, and gradually in the rest of the body. The rash finally rises and turns into pus-filled blisters.
Each pustule contains live virus and a broken bottle can contaminate bedding and other items, putting close contacts at risk. Infected people should also be very careful not to rub their eyes because the virus can destroy vision.
“Before Jenner developed the smallpox vaccine, the leading cause of blindness in the world was smallpox,” said Mark Slifka, an immunologist at Oregon University of Health and Science. Infected people are contagious until the pustules run out and fade, he said.
Dr. Slifka and other experts pointed out that while the smallpox of the monkey can be severe and even fatal, the current outbreak is unlikely to swell into a major epidemic.
“We’re lucky to have vaccines and therapeutics, things that can mitigate all of that,” said Anne Rimoin, an epidemiologist at the University of California, Los Angeles, who has studied monkeypox in Africa. “We have the ability to stop this virus.”
The monkeypox takes up to 12 days to cause symptoms, giving doctors a period of at least five days after exposure to vaccinate and prevent disease. (The approach, called post-exposure prophylaxis, is not an option for patients with Covid because the coronavirus can start to hit the body only a couple of days after exposure).
The smallpox virus does not spread in the absence of symptoms. Careful surveillance, isolation of infected people, follow-up of contacts, and quarantine of contacts should contain the outbreak, Dr. Rimoin said.
Currently, most of the infected are men under the age of 50, and many identify as gay or bisexual, which may reflect the possible origins of the outbreak at a Gay Pride event in the Canary Islands. (The outbreak could have started just as easily among heterosexuals at a big event, experts said.)
“Exposure risk is not limited to any particular group,” Dr. Walensky Thursday. “Our priority is to help everyone make informed decisions to protect their health and the health of their community, and that starts with creating science-driven awareness, not stigma.”
No deaths were reported. But experts are especially concerned about close contacts who are children, older adults, or who have a weak immune system for other reasons.
There are conflicting opinions about how long a smallpox vaccine’s immunity lasts.
The CDC recommends strengthening smallpox vaccines every three years, but only “for people at risk of occupational exposure,” David Daigle, a spokesman for the agency, said in a statement.
“Until we know more, we will use the available vaccine stocks for people who have had close contact with known cases and people at higher risk of exposure through their work, such as health care workers who treat smallpox patients. monkey, “he said.
The United States and several European countries have begun to immunize close contacts of infected patients, an approach called ring vaccination.
Many of the most vulnerable groups are already protected. In one study, Dr. Slifka and colleagues extracted blood from 306 vaccinated volunteers, some of whom had been immunized decades earlier, including one who had been vaccinated 75 years earlier. Most of them maintained high levels of antibodies against smallpox.
In another study, Dr. Slifka and her colleagues showed that antibodies produced by even a single dose of the smallpox vaccine slowed down very slowly in the body, falling by half after about 92 years.
Dr. Ferrucci and colleagues at the NIH, as well as other teams, have also found that antibody levels persist for decades after vaccination. Some studies have found that other branches of the immune system also slow down, but the antibodies produced by smallpox vaccination may be enough on their own to protect themselves from monkeypox.
If the smallpox began to spread, it would make sense to immunize anyone exposed to its high mortality rate, regardless of a previous vaccination, said Gigi Gronvall, a biosecurity expert at the Johns Hopkins Center for Health Security.
What you need to know about the monkeypox virus
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What is the smallpox of the monkey? Smallpox is an endemic virus in parts of Central and West Africa. It is similar to smallpox, but less severe. It was discovered in 1958, after outbreaks of monkeys kept for research, according to the Centers for Disease Control and Prevention.
What are the symptoms? Monkeypox creates a rash that begins with flat red markings that rise and fill with pus. Infected people may also have a fever and body aches. Symptoms usually appear between six and 13 days, but can take up to three weeks after exposure and can last between two and four weeks. Health officials say smallpox vaccines and other treatments can be used to control an outbreak.
How contagious is it? The virus spreads through body fluids, skin contact and respiratory drops. It does not usually cause major outbreaks, although this year it has spread in unusual ways and among populations that have not been vulnerable in the past.
Do I have to worry? The virus is likely to spread during sexual intercourse, but the risk of transmission in other ways is low. Most people have mild symptoms and recover within a few weeks, but the virus can be fatal in a small percentage of cases.
“We wouldn’t want to run the chance of someone being left unprotected,” he said.
But that’s not necessary now, he added: “This is the monkey’s smallpox.”
Laboratory antibody tests do not show that smallpox vaccination can protect against smallpox. But answering this question would require that study participants be deliberately infected with smallpox or a related virus, an obviously unethical experiment.
For the same reason, only the most recent smallpox vaccines and drugs have been tested in animals.
However, one way to study the effectiveness of the vaccine in people is to gather evidence during an outbreak. Dr. Slifka’s team did just that in 2003, when dozens of Americans became infected with monkeypox after being exposed to dogs on infected prairies.
Investigators flew to Milwaukee and extracted blood from 28 people who had been exposed to dogs on infected prairies. Of the eight people who had been previously vaccinated, five developed an average of three blisters full of pus, compared with an average of 33 in those who had not been vaccinated.
The other three vaccinated individuals had no symptoms. “They didn’t even know they had been infected,” Dr. Slifka said.
Another study of this outbreak found that in a family of three, the previously vaccinated father developed only two smallpox lesions from the monkey compared to the 200 from the unvaccinated mother. Her unvaccinated 6-year-old daughter had about 90 injuries and was in a coma for 12 days.
Questions about the durability of monkeypox vaccine protection have become especially important as the number of cases worldwide has increased. Smallpox of the monkey reappeared among people in Nigeria in 2017, and since then there have been about 200 confirmed cases and 500 suspected cases.
The Democratic Republic of the Congo has reported 58 deaths and nearly 1,300 suspected cases since the beginning of this year.
People in African villages used to get smallpox from the monkeys of the animals while hunting, but rarely infected others. “It’s only very recently, like the last few years, that we started seeing this,” Dr. Rimoin said of larger outbreaks.
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