On Friday, officials at the Centers for Disease Control and Prevention objected to the idea that the monkey smallpox virus could be spread through the air, saying the virus is usually transmitted from a person through direct physical contact with wounds or contaminated materials.
The virus can also be transmitted through inhaled droplets from a patient who has been in physical contact with another person, they said. However, it cannot travel long distances.
Experts on airborne transmission of the virus are divided, but some say the agency did not fully consider the possibility of large or small respiratory drops being inhaled at short distances from the patient.
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The World Health Organization and several experts say that short-term airborne transmission of smallpox is rare, but it is possible and requires precautions. Britain also includes smallpox on its list of “high-risk infectious diseases” that can be spread through the air.
“Airborne transmission is not the dominant route or is not very effective, but it can still happen,” said Lincie Marr, an airborne virus expert at Virginia Tech.
“I think the WTO is right and the CDC’s statement is wrong,” he added.
The monkey epidemic in the United States has increased to 45 cases in 15 states and the District of Columbia, CDC officials said at a news conference. Since May 13, when the first case was registered, the global rate has grown rapidly to more than 1,450. At least 1,500 cases are still under investigation.
Historically, people with monkey pox have reported symptoms of the flu before the typical rash appeared. However, some patients in the current epidemic initially developed rashes, and some did not have these symptoms at all, the doctor said. CDC Director Rochelle Valensky made the announcement on Friday.
No casualties have been reported in the current epidemic, he said.
Questions about airborne transmission of the monkey smallpox virus are important because the answers, in turn, are based on recommendations for masking, ventilation, and other protective measures in the event of an epidemic.
The CDC said on Thursday that smallpox “does not last long in the air and does not infect the general airspace in the short term.” The announcement followed an article in the New York Times on Tuesday in which scientists described uncertainties about the spread of the virus.
“What we do know is that in the current epidemic, monkeys have described a close, stable physical contact with other people who have been infected with the virus,” Valensky said on Friday. “This is in line with what we’ve seen in previous epidemics and what we’ve been studying for decades about this virus and the viruses around it.”
However, monkey smallpox has been poorly studied, and other experts say that the smallpox virus is transmitted through the air. In a Nigerian smallpox epidemic in 2017, two health workers who were not in direct contact with patients became infected, scientists said at a recent WHO conference.
In the current epidemic, several people do not know when and how they became infected, CDC patients admitted.
The agency should reassure the public that the epidemic is not a threat to most people because monkeys are not as contagious as coronavirus, the doctor said. Donald Milton, an expert on the spread of the virus through the air at the University of Maryland.
Milton said airborne infections posed no immediate threat to anyone but caregivers, but warned that rejecting the possibility altogether was “the wrong way to go.”
According to Milton and other experts, when the virus is found in saliva or in the respiratory tract, monkeys have been shown to be smallpox, which can be released by respiratory droplets when speaking, singing, coughing or sneezing.
Drops can be heavy and fall quickly on objects or people, or they can be small and light, and can withstand long distances and distances in the air. The cost of CDC is partly due to the presence of the virus in large droplets or very small droplets called aerosols.
At the beginning of a similar controversy over the coronavirus pandemic, the agency and the WHO focused on large drops as the main route of transmission. But aerosols turned out to be the main engine.
The new CDC guidelines for smallpox describe the respiratory droplets released by patients as “rapid secretions from the air.”
But Lydia Moravska, an air quality expert at Queensland University of Technology in Australia, said the virus was not just in large droplets, but “in the size of respiratory particles.”
“I don’t think there is any reason to say that the virus can only be transmitted by large droplets and that the risk of infection is only at close range,” he wrote in an email.
CDC officials said on Friday that patients in the current epidemic appear to have been infected through close, constant contact. However, this can be difficult to determine.
When people are in close contact, it is impossible to tell if they have been infected by touching the virus, spraying large droplets or inhaling aerosols, Marr said.
“In such cases, the infection does not determine how the virus is transmitted from one person to another,” he said. If the infection can be caused by inhalation, “it can also be caused by inhalation of aerosols.”
However, most experts believe that no matter what the contribution of inhaled aerosols, monkeys cannot be infected at a distance that could be a coronavirus or a measles virus.
“I agree that smallpox can be caused by touch – direct contact between the mucous membranes,” Milton said.
But “the CDC seems to be stuck with the old terminology,” he said. “We need to talk about giving it through touch, spray or inhalation, using terms that really make it clear how it will be.”
In its advice to clinics, the CDC acknowledges the possibility of short-term airborne transmission. The agency recommends that patients wear masks and that caregivers wear N95 respirators, which are needed to filter aerosols.
He also warns that “procedures that could spread oral secretions should be performed in an airborne infection isolation room.”
There is evidence that smallpox can live in aerosols and that inhalation viruses can cause disease in monkeys. However, airborne transmission for the monkey smallpox virus is not ideal.
Patients may not produce much of the virus in aerosols, the virus may not remain infectious for long, or the amount of inhaled virus needed to infect someone may be too high, Marr said.
In this case, airborne transmission can occur only in people who have been close for a long time. However, British health officials said that as in the United States, many patients did not know when and where they became infected.
If they were infected without close contact, “there could be more airborne infections than we thought,” Marr said.
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