The Centers for Disease Control and Prevention has identified 21 monkeypox cases in 11 states, and the numbers are expected to rise, officials reported on Friday.
Genetic analysis has revealed that while most cases appear to be closely related to the outbreak in Europe, two patients have versions of the virus that seem to have evolved from a monkeypox case identified in Texas last year.
Of 17 patients for whom the agency has detailed information, all but one were men who had sex with men; 14 had traveled to other countries in the three weeks before their symptoms began. Three patients were immunocompromised.
CDC researchers have not been able to identify how a patient in an unnamed state has acquired the virus. That suggests there is an ongoing community transmission at least in that state and possibly others, Dr. Jennifer McQuiston of the CDC told reporters.
“We really want to increase our surveillance efforts,” she said.
Health officials have identified a total of about 400 contacts of 13 patients who are also at risk of being infected with monkeypox. Identifying contacts at risk will help officials determine what resources are required to contain the outbreak.
So far, health officials have delivered about 1,200 vaccine doses and 100 treatment courses to eight states, according to Dr. Raj Panjabi, Senior White House Director for Global Health Security and Biodefense.
Monkeypox’s toll worldwide rose sharply this week, to nearly 800 cases as of Friday. The spread of the virus to at least 31 countries outside Africa, where it is endemic, has raised alarm among scientists and public health officials.
Health officials in some countries are asking anyone who tests positive for monkeypox to isolate at home. Britain, which has recorded most cases, urges patients to abstain from sex until their symptoms are cleared, to use condoms for eight weeks after that and to limit interactions with pets and other animals, which may become infected.
As the outbreak expands, health officials are gathering around vaccines and treatments to protect infected people and their close contacts. The options are severely limited.
The United States is among the few countries to have stockpiled millions of doses of vaccines and drugs for smallpox as a precaution against its return. Monkeypox is closely related to smallpox, and the vaccines and drugs are expected to be about as effective.
In theory, at least two drugs and two types of vaccines are available to combat a monkeypox outbreak, but most of these have been tested successfully in animals.
In a recent study of two drugs in seven patients, only one appeared to offer any benefit, while the other produced toxic side effects.
The older of the two vaccine options was used to eradicate smallpox and can cause harsh side effects, including heart problems and death. Most doses have been stored for decades and may have lost their effectiveness.
The second vaccine option, made by the Danish company Bavarian Nordic, was approved by the Food and Drug Administration in 2019 to prevent smallpox and monkeypox. Called Jynneos in the United States, it is safer than before vaccines, but supplies are even more limited.
Several countries, including Canada, Britain and France, have already begun vaccinating close contacts of infected people, and many others have placed orders for additional supplies for the Bavarian Nordic.
Several experts noted that African countries that have battled monkeypox for years have had little access to these vaccines and treatments. So far this year, 44 cases have been recorded in Nigeria and six other African countries where the virus is endemic, but those numbers are likely to be an underestimate.
The monkeypox outbreak in western countries may further limit access to vaccines and treatments in poorer countries, some experts fear. “Vaccines and treatments that are being stockpiled elsewhere are not necessarily shared,” said Dr. Ifedayo Adetifa, Director of the Nigeria Center for Disease Control.
In Switzerland, the World Health Organization maintains about 2.4 million doses of vaccine used to eradicate smallpox, and it has stockpiled another 31 million doses in five donor countries that could be released to countries.
But the WHO had recently recommended the vaccine only for people at high risk exposure, said Tarik Jašarević, a spokesman for the organization. Experts convened by the WHO to schedule guidance in October, but “that timeline will need to be sped up,” he said.
The WHO is also assessing the newer Jynneos vaccine for prequalification, a step needed for its use in many countries.
Scientific advisers to CDC voted in November to recommend Jynneos for immunizing researchers and health care personnel who are at risk of exposure to smallpox or monkeypox.
The US emergency stockpile holds 100 million doses of an older smallpox vaccine called ACAM2000. But the vaccine contains live vaccinia virus, and causes about six cases of myopericarditis – inflammation of the heart muscle – for every 1,000 people who receive it.
ACAM2000 cannot be used in pregnant women, infants or those who are immunocompromised – exactly the people who most need protection from the monkeypox virus.
Jynneos, by contrast, has been shown to be safe in older adults, people with HIV or AIDS and those who have received bone marrow transplants and are therefore immunocompromised.
The US stockpile once held 28 million doses of Jynneos, but those doses have all expired, according to Paul Chaplin, Bavarian Nordic’s chief executive. Federal health officials have said about 1,000 doses of Jynneos are available, but Bavarian Nordic has delivered thousands more in the past weeks, according to Dr. Chaplin.
In all, the United States has access to about a million doses, he said.
People infected with monkeypox can be vaccinated for even a few days after exposure. They can also be treated with one of two drugs approved to treat smallpox, tecovirimat and brincidofovir, which slow down the virus and buy the immune system over time.
What to Know About the Monkeypox Virus
What is monkeypox? Monkeypox is a virus endemic in parts of Central and West Africa. It is similar to smallpox, but less severe. It was discovered in 1958, after outbreaks occurred in Monkeys for research, according to the Centers for Disease Control and Prevention.
The FDA has approved an oral form of tecovirimat, also called Tpoxx, to treat smallpox in adults and children who weigh at least 13 kilograms, or 28.6 pounds, although the drug was never tested in children.
The drug, made by the New York-based company Siga Technologies, is taken twice daily for 14 days, and in safety tests it does not appear to have serious side effects beyond gastric symptoms.
The US stockpile holds 1.7 million courses of tecovirimatGeneral Chat Chat Lounge On May 12, before the monkeypox outbreak emerged, the Department of Defense procured another $ 7.5 million in drug courses, about half of which were to be delivered this year.
“A significant number of countries” have requested courses of the drug since the outbreak began, said Dennis Hruby, chief scientist at Siga. By the end of June, the company expects to distribute up to 190,000 treatment courses, he said.
The FDA worked with Siga to develop an intravenous formulation and approved it on May 19. This version can be used in patients who cannot take oral medication because of blisters in their mouths.
Health Canada, the national health department, approved tecovirimat in 2020 and has purchased $ 13 million worth of doses, according to Dr. Hruby. The European Medicines Agency also endorsed the drug in January to treat all orthopox viruses – the viral family that includes both smallpox and monkeypox – but was still negotiating with the company when the outbreak emerged.
Tecovirimat and brincidofovir were both approved under the FDA’s Animal Rule, which allows the agency to rely on data from rodents or monkeys when it is unethical to test a drug in people.
The second drug, brincidofovir, is made by Chimerix and appears to have more side effects, including a risk of death, prompting the agency to issue a so-called black box warning – its most stringent warning – on the drug’s use.
In a recent study of both drugs, brincidofovir “was not observed to have any convincing clinical benefit,” researchers reported. But the study was too small and the treatment regimens offered to patients were too varied to draw any conclusions about the efficacy of the drugs, said David Evans, a virologist at the University of Alberta who consults for Chimerix.
Those who cannot safely take either tecovirimat or brincidofovir – people who are immunocompromised, for example – can be given an immune therapy called vaccinia immunoglobulin, but only limited quantities exist.
The United States is developing a cocktail of monoclonal antibodies that can block the monkeypox virus. Several vaccines are also in development at an early stage, including some that rely on horsepox.
In the long run, it may make sense for the United States to stockpile enough vaccines and drugs to protect the entire population – including those who may have been vaccinated for smallpox in childhood, said Dr. Seth Lederman, chief executive of Tonix, which is developing a horsepox-based vaccine.
Multiple studies suggest that people who have been vaccinated for smallpox may be protected from serious illness, if not infection. But developing even a few lesions would be enough to spread the virus to others, Dr. Lederman noted.
“In the case of something like monkeypox, I think that would be the goal so that people don’t get lesions,” he added.
Tonix’s vaccine will not be available for use in the current outbreak. “Our approach will be to go slow and steady,” he said. “These problems are not going away.”