Monkeypox and future pandemics
Published May 31, 2022 12:05 am
CLINICAL MATTERS
The Covid-19 pandemic hasn’t ended and now we are starting to see the emergence and re-emergence of new infectious disease threats. The most recent infection to capture the public’s attention is monkeypox.
Monkeypox is not a new disease. It was first described in Africa as a disease transmitted by rodents. The incubation period from exposure to manifestation of symptoms is five to 21 days. The disease starts as a flu-like illness. This is followed by a vesicular rash that breaks out all over the body after a few days, frequently accompanied by lymph node swelling. The disease typically resolves in about two to four weeks in healthy patients. Monkeypox can infect primates, rodents, and other animals. It was named monkeypox since it was first described in monkeys being housed in a laboratory. Human-to-human transmission is relatively rare. Outbreaks outside endemic areas do occur and may cause panic since these may be mistaken for smallpox or a bioterrorism attack.
Monkeypox is part of the orthopoxvirus family that includes smallpox and cowpox. While it may look like chickenpox, it is not related to varicella-zoster (the virus that causes chickenpox), which is part of the herpes virus family. The smallpox vaccine made up of the cowpox virus works against monkeypox about 85 percent of the time. The vaccine can be given up to four days after exposure and can prevent the development of symptoms. As a historical side note, the smallpox vaccine is derived from the cowpox virus. The cowpox virus is also known as Vaccinia, and this is the root word of the term “vaccine.”
When I was training in internal medicine in Milwaukee in 2003, we had a few monkeypox patients who were part of a larger outbreak in the US. Many of these patients had acquired monkeypox from prairie dogs that were in turn infected by rodents imported from Africa. While there was substantial panic since it was first thought to be smallpox, the virus was eventually identified as monkeypox. The outbreak was contained and there were no fatalities. There was a renewed flurry of interest in monkeypox at that time but it eventually waned when there were no other cases.
Since then, there have been sporadic outbreaks worldwide. The disease is endemic in West Africa and Central Africa. Some strains from the Democratic Republic of the Congo can have mortality rates of up to 10 percent, while the Western African clades are less virulent. Imported cases are also less deadly, with a mortality of one percent or less. The current reported cases of monkeypox are unusual in that there are several clusters in different countries. All the cases are in men and might be linked to sexual activity.
Transmission of monkeypox is via direct contact, indirect contact, or large respiratory droplets. Direct contact with the pox lesions can transmit the virus through non-intact skin or exposed mucous membranes like those on the eyes, nose, mouth, or genital tract. Indirect contact is through contaminated clothes and other items that transmit through non-intact skin or mucous membranes. Large respiratory droplet transmission can occur when someone with monkeypox coughs or sneezes and close contact inhales these droplets. Monkeypox is not efficiently transmitted at longer distances, and a face mask will prevent transmission. It is not traditionally thought of as a sexually transmitted disease and so the recent reports of possible sexual transmission are unusual. Since sexual activity, however, does involve close contact, it is plausible the current outbreak is related to this.
Monkeypox is a DNA virus, in contrast to SARS-CoV-2, which is an RNA virus. This means that its genome is more stable and less likely to give rise to mutations that may make it deadlier or more transmissible. Current genomic work on the clusters of monkeypox cases seems to point to a common origin. These need to be confirmed since sequencing monkeypox is also a complicated process and takes time.
There is no need to widely vaccinate with the smallpox vaccine currently. The risk remains small and cases can be contained with proper contact tracing. While the smallpox vaccine is effective against monkeypox, it is made up of a weakened live cowpox virus that can still cause cowpox. There is a small but real risk of a vaccine-related serious cowpox infection, especially for those with weakened immune systems. Given the low numbers and relatively mild course of monkeypox, mass vaccination with the smallpox virus is not justified at this time. Close contacts of cases can be offered the smallpox vaccine within four days of exposure, particularly those who may be at risk for severe outcomes. The Philippines currently has no stockpiled smallpox vaccines. The government, however, is coordinating with different countries that have smallpox vaccine stockpiles in case the need arises. No cases of monkeypox have been detected locally at the time this article was written.
Drugs that have been proven to work against smallpox may also work against monkeypox. Cidofovir and brincidofovir are two drugs that are expected to have some activity. Another smallpox drug, tecovirimat, is approved for monkeypox infection in Europe but not in the US. Vaccinia immunoglobulin may also be an option, although there is little hard data available on its effectiveness. None of these drugs are available locally but may be procured in an emergency.
So is monkeypox the next Covid-19? This is highly unlikely. Monkeypox is much less transmissible, less virulent, and not prone to mutation compared to Covid-19. Since it is a re-emerging infectious disease, vaccines and treatments already exist. Since it has a longer incubation period than Covid-19, contact tracing has a better chance of containment of exposed cases.
Current precautions to prevent Covid-19, including symptom screening of travelers, especially from outbreak areas, and the continued use of face masks will protect against monkeypox. Nevertheless, it is important to be vigilant. Aside from the threat of monkeypox, new variants of Covid-19 can emerge at any time. Seasonal and avian influenza are always lurking and can trigger a new pandemic. There is no need to panic as long as we have prevention measures in place and we have knowledgeable and dedicated healthcare workers. New diseases and re-emerging old diseases are a fact of life. Living with these viruses and minimizing their impact on our daily lives are the challenges we must meet head-on.
The Covid-19 pandemic hasn’t ended and now we are starting to see the emergence and re-emergence of new infectious disease threats. The most recent infection to capture the public’s attention is monkeypox.
Monkeypox is not a new disease. It was first described in Africa as a disease transmitted by rodents. The incubation period from exposure to manifestation of symptoms is five to 21 days. The disease starts as a flu-like illness. This is followed by a vesicular rash that breaks out all over the body after a few days, frequently accompanied by lymph node swelling. The disease typically resolves in about two to four weeks in healthy patients. Monkeypox can infect primates, rodents, and other animals. It was named monkeypox since it was first described in monkeys being housed in a laboratory. Human-to-human transmission is relatively rare. Outbreaks outside endemic areas do occur and may cause panic since these may be mistaken for smallpox or a bioterrorism attack.
Monkeypox is part of the orthopoxvirus family that includes smallpox and cowpox. While it may look like chickenpox, it is not related to varicella-zoster (the virus that causes chickenpox), which is part of the herpes virus family. The smallpox vaccine made up of the cowpox virus works against monkeypox about 85 percent of the time. The vaccine can be given up to four days after exposure and can prevent the development of symptoms. As a historical side note, the smallpox vaccine is derived from the cowpox virus. The cowpox virus is also known as Vaccinia, and this is the root word of the term “vaccine.”
When I was training in internal medicine in Milwaukee in 2003, we had a few monkeypox patients who were part of a larger outbreak in the US. Many of these patients had acquired monkeypox from prairie dogs that were in turn infected by rodents imported from Africa. While there was substantial panic since it was first thought to be smallpox, the virus was eventually identified as monkeypox. The outbreak was contained and there were no fatalities. There was a renewed flurry of interest in monkeypox at that time but it eventually waned when there were no other cases.
Since then, there have been sporadic outbreaks worldwide. The disease is endemic in West Africa and Central Africa. Some strains from the Democratic Republic of the Congo can have mortality rates of up to 10 percent, while the Western African clades are less virulent. Imported cases are also less deadly, with a mortality of one percent or less. The current reported cases of monkeypox are unusual in that there are several clusters in different countries. All the cases are in men and might be linked to sexual activity.
Transmission of monkeypox is via direct contact, indirect contact, or large respiratory droplets. Direct contact with the pox lesions can transmit the virus through non-intact skin or exposed mucous membranes like those on the eyes, nose, mouth, or genital tract. Indirect contact is through contaminated clothes and other items that transmit through non-intact skin or mucous membranes. Large respiratory droplet transmission can occur when someone with monkeypox coughs or sneezes and close contact inhales these droplets. Monkeypox is not efficiently transmitted at longer distances, and a face mask will prevent transmission. It is not traditionally thought of as a sexually transmitted disease and so the recent reports of possible sexual transmission are unusual. Since sexual activity, however, does involve close contact, it is plausible the current outbreak is related to this.
Monkeypox is a DNA virus, in contrast to SARS-CoV-2, which is an RNA virus. This means that its genome is more stable and less likely to give rise to mutations that may make it deadlier or more transmissible. Current genomic work on the clusters of monkeypox cases seems to point to a common origin. These need to be confirmed since sequencing monkeypox is also a complicated process and takes time.
There is no need to widely vaccinate with the smallpox vaccine currently. The risk remains small and cases can be contained with proper contact tracing. While the smallpox vaccine is effective against monkeypox, it is made up of a weakened live cowpox virus that can still cause cowpox. There is a small but real risk of a vaccine-related serious cowpox infection, especially for those with weakened immune systems. Given the low numbers and relatively mild course of monkeypox, mass vaccination with the smallpox virus is not justified at this time. Close contacts of cases can be offered the smallpox vaccine within four days of exposure, particularly those who may be at risk for severe outcomes. The Philippines currently has no stockpiled smallpox vaccines. The government, however, is coordinating with different countries that have smallpox vaccine stockpiles in case the need arises. No cases of monkeypox have been detected locally at the time this article was written.
Drugs that have been proven to work against smallpox may also work against monkeypox. Cidofovir and brincidofovir are two drugs that are expected to have some activity. Another smallpox drug, tecovirimat, is approved for monkeypox infection in Europe but not in the US. Vaccinia immunoglobulin may also be an option, although there is little hard data available on its effectiveness. None of these drugs are available locally but may be procured in an emergency.
So is monkeypox the next Covid-19? This is highly unlikely. Monkeypox is much less transmissible, less virulent, and not prone to mutation compared to Covid-19. Since it is a re-emerging infectious disease, vaccines and treatments already exist. Since it has a longer incubation period than Covid-19, contact tracing has a better chance of containment of exposed cases.
Current precautions to prevent Covid-19, including symptom screening of travelers, especially from outbreak areas, and the continued use of face masks will protect against monkeypox. Nevertheless, it is important to be vigilant. Aside from the threat of monkeypox, new variants of Covid-19 can emerge at any time. Seasonal and avian influenza are always lurking and can trigger a new pandemic. There is no need to panic as long as we have prevention measures in place and we have knowledgeable and dedicated healthcare workers. New diseases and re-emerging old diseases are a fact of life. Living with these viruses and minimizing their impact on our daily lives are the challenges we must meet head-on.