On June 27th, I reported on the recent outbreak of monkeypox which began in England in May with the first case being identified in a traveler returning from Nigeria. In that article, I gave a brief history of the disease. You can read it on my blog www.WMillerMD.com, which includes all my previous articles. At that time, there were about 3,500 cases worldwide, with 244 being identified in the US and 66 in California.
In the two months or so since then, the number of cases has significantly increased with now over 47,600 cases reported worldwide and spread out over 99 countries. The US has the highest number of reported cases at 18,400, followed by Spain with 6,400, Brazil with just under 4,000, and France, Germany, and the UK at just over 3,000 each. This may paint a somewhat skewed impression that the US has a worse outbreak, since the US has some of the most rigorous reporting requirements for contagious diseases and has also been quick to mobilize test kits to hospitals to test for the disease. In other words, there are most likely cases in other countries that are going undetected or unreported. None the less, it is certainly an impressive increase.
The two states with the highest number of cases are New York, with 3,100 and California with 3,300. Florida, Texas, Georgia, and Illinois have each reported over 1,000 cases.
Most of the new cases were in July, leading the World Health Organization (WHO) to declare it a worldwide health emergency on July 23rd. During that month, the case rate almost doubled each week. However, this began to level off in the first week of August and the last two weeks have seen an actual decrease in the number of new cases per week. Sixteen countries have had no new cases in the past 21 days.
Monkeypox is spread through close physical contact with someone who is infected and has pustules on their skin. While it is not sexually transmitted per se, the more intimate the physical contact, the more likely the chance of transmission which is estimated to be about 10%. Recall that the omega variant of COVID has about a 50% transmission rate and is spread through the air as respiratory droplets. There have been a few cases of monkeypox reported where the spread may have been through respiratory droplets, but this is rare.
The WHO is reporting that about 95% of cases during this current outbreak have been in men who have sex with men and that the transmission occurred during sexual contact. This is strong evidence that this disease is not being spread through casual contact, surfaces, or respiratory droplets in any significant way. The WHO also reported in its weekly update, that it suspects that the decrease in new cases seen over the past two weeks has been a result of education to the gay community and a prompt change in behavior to limit the number of sexual partners by those men who routinely have multiple partners.
Monkeypox is an illness that, like chickenpox, has an extremely low mortality rate. Despite almost 50,000 worldwide cases thus far, there have only been 12 deaths reported. Seven in Africa, two in the Americas (one US death was in Texas), two in Europe and one in Asia. Like chickenpox, the illness causes a fever, swollen lymph nodes and a painful, pustular rash. Most hospitalizations in the US and Europe have been for pain control. In Africa, where untreated HIV and AIDS remains a significant problem, hospitalizations have been for treatment of secondary consequences such as dehydration and pneumonia. This is similar to a previous outbreak of monkeypox in Western Africa during the 1970’s.
For those of us who have become amateur virologists over the past two years, monkeypox is a virus in the genus orthopoxvirus, which includes the variola virus that causes smallpox, varicella virus that causes both chickenpox and shingles, and vaccinia virus that causes cowpox. It was first identified in the late 1950’s in a research lab in Denmark that was using monkeys from Singapore to study polio. The first cases in humans were identified in early 1970 during the above-mentioned outbreak in Africa.
It is thought to have first jumped from monkeys to a small rodent, perhaps a squirrel, in the Congo region of Central Africa and then on to humans. This variant has been named clade I and may cause a more severe illness in humans. The 1970’s outbreak in Western Africa has been dubbed clade IIa. The variant causing the current worldwide outbreak is clade IIb. The word “clade” derives from a Greek word meaning “one clan” and is used as a scientific term referring to groups of similar organisms with the same genetic ancestor.
Unlike corona viruses and influenza viruses, which have a very high mutation rate, orthopox viruses have a relatively low mutational rate. There are several biological reasons for this, but a major one is the type of genetic material they contain. Orthopox viruses contain double-stranded DNA. DNA is a more chemically stable molecule. Also, the fact that there are two strands coiled around each other allows for a check to be made when the genes are copied. If an error has occurred, then it can be corrected as a result and a mutation avoided. This is referred to as “fidelity”. Both corona and influenza viruses are single-stranded RNA. RNA is an inherently less stable molecule and the lack of a second strand by which to check the fidelity of replication leads to more frequent mutations. Interestingly, this is actually an evolutionary strategy employed by these two viral groups, since high mutation rates allow for the virus to be constantly changing and thus avoiding the host’s attempts to resist infection. The bottom line, however, is that monkeypox is not likely to go through the same frequent mutations to new variants like we have seen with COVID.
Comentarios