Feature

Asymptomatic infections drive many epidemics, including monkeypox, polio, and COVID


 

Monkeypox

Monkeypox cases have been skyrocketing in the United States in recent weeks. More than 18,000 cases have been reported since the first case in Boston on May 19, 2022.

“Monkeypox was such a rare zoonotic disease, and the disease always historically was introduced through animal contact,” Stuart Isaacs, MD, a pox virologist at the University of Pennsylvania, said in an interview. “And then the infected person would have potential spread within the household as the most common human-to-human spread, The sexual transmission is driving a lot of this infection and potentially allowing this to efficiently spread from person to person.”

A recent study from Belgium, available only as a preprint, created concerns about potential asymptomatic transmission of monkeypox Three men had undergone testing for anogenital chlamydia and gonorrhea but showed no clinical signs of monkeypox. The same samples were later tested by polymerase chain reaction (PCR), and their viral load in anorectal swabs was similar to or slightly lower than that of symptomatic patients. While no cultures were done, the patients seroconverted by later antibody testing, confirming infection.

Via email, a CDC spokesperson noted, “At this time, CDC does not have enough data to support transmission from aerosolized virus for the ongoing monkeypox outbreak, or to assess the risks for transmission from asymptomatic people. The data supports the main source of transmission currently as close contact with someone who is infected with monkeypox.”

Dr. Isaacs agreed, saying studies of smallpox, a related orthopox virus, also suggested this.

In the United Kingdom, the Institute of Tropical Medicine is offering PCR testing for monkeypox to all patients who come for gonorrhea/chlamydia screening. Dr. Racaniello said, “I think that would be great to get a sense of who is infected. Then you could look at the results and say what fraction of people go on to develop lesions, and they give you a sense of the asymptomatic rate, which we don’t know at this point.”

Unfortunately, to be tested for monkeypox in the United States requires that the patient have a lesion. “This is part of the dropped ball of public health in the U.S.,” Dr. Racaniello said. “We’re not thinking about this. .... We need to be doing [infectivity] experiments. So then the question is, how much infectious virus do you need to transmit?”

Conclusion

We’ve seen that asymptomatic carriage of bacteria and viruses occurs readily with typhoid, COVID, diphtheria, and polio (among many other organisms, such as methicillin-resistant Staphylococcus aureus or group A strep) and is far less likely with monkeypox.

Two common denominators emerged from these interviews. The first and biggest hurdle is identifying asymptomatic carriers, which is hampered by the politicization of the CDC and funding cuts to public health. “It used to be the CDC was all about public health, and now it’s administrators, unfortunately,” said Dr. Racaniello, citing science writer Laurie Garrett, author of the influential 1994 book, “The Coming Plague”.

We don’t conduct proper surveillance, he pointed out. Wastewater surveillance has been neglected for more than a decade. It has been used for SARS-CoV-2 but is only now being initiated for polio and monkeypox. Norovirus testing would also be especially helpful in reducing foodborne outbreaks, Dr. Racaniello suggested.

The second common denominator is the need to increase the availability and uptake of vaccines. As Dr. Racaniello said about COVID, “The virus is here to stay. It’s never going to go away. It’s in humans. It’s in a lot of animals. So we’re stuck with it. We’re going to have outbreaks every year. So what do you do? Get vaccinated.” And he added, “Vaccination is the most important strategy to go on with our lives.”

Dr. Isaacs was a bit more tempered, not wanting to oversell the vaccine. He said, “The vaccine is just part of the toolkit,” which includes education, testing, isolation, and reducing risk, all of which decrease the transmission cycles.

Speaking of how antivaccine advocates had specifically targeted the Hasidic community in New York State’s Rockland County, Dr. Offit noted, “I don’t think it’s a knowledge deficit as much as a trust deficit.” He said officials should identify people in communities such as these who are trusted and have them become the influencers.

The final major hurdle to controlling these outbreaks remains global disparities in care. Monkeypox has been endemic in Nigeria for decades. It was only when it spread to Europe and America that it received attention. Polio has been actively circulating in Africa and the Middle East but is only getting attention because of the New York case.

Africa was unable to afford COVID vaccines until recently. While many in the United States are on their fourth booster, as of December 2021, more than 80% of people in Africa had not yet received a single dose, according to an article by Munyaradzi Makoni in The Lancet Respiratory Medicine.

Echoing Dr. Peter Hotez’s long-standing plea for “vaccine diplomacy,” Dr. Racaniello concluded, “My philosophy has always been we should give [vaccines] to them. I mean, we spend trillions on guns. Can’t we spend a few hundred million on vaccines? We should give away everything in terms of medicine to countries that need it, and people would like us a lot better than they do now. I think it would be such a great way of getting countries to like us. … So what if it costs a billion dollars a year? It’s a drop in the bucket for us.”

Given globalization, an infectious outbreak anywhere is a risk to all.

Dr. Racaniello and Dr. Offit report no relevant financial relationships. Dr. Isaacs receives royalties from UpToDate.

A version of this article first appeared on Medscape.com.

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