Even as mpox clade 1b takes center stage from Covid-19, new SARS-CoV-2 variants are constantly being generated as it continues to circulate in the community. It is expected that Covid-19 will eventually settle into a seasonal pattern, although new novel lineages can cause spikes in cases at any given time. The latest candidate for becoming a dominant SARS-CoV-2 variant is the recombinant lineage XEC. This lineage was first detected in Germany and is now working its way through Western Europe and the UK and seems to have a survival advantage over other circulating sublineages.

XEC is still part of the Omicron family and is a result of the recombination of Omicron sublineages KP.3.3 and KS.1.1. Recombination of SARS-CoV-2 viruses occurs when a person is simultaneously infected with two different viruses. If two different viruses infect the same cell, they can end up mixing their genetic material and a new recombinant virus is produced. If the recombinant virus has mutations that confer a survival advantage over other circulating sublineages, it can take over and become the dominant circulating sublineage.

The first significant recombinant lineages were XC (a combination of Alpha B.1.1.7 and Delta AY.29), XD (the so-called Deltacron, because it was a combination of Delta AY.4 and Omicron BA.1), followed by XE (BA.1 and BA.2), and others. The XBB lineage, especially the XBB.1.5 sublineage, had a survival advantage over other circulating viruses and quickly became a dominant variant in early 2023. Thankfully, despite the abundance of mutations that allowed these recombinants to avoid the immune system, vaccination and boosting continued to protect people from severe disease and death. Moreover, none of these recombinants caused worse disease or were associated with higher mortality. The same treatments, like remdesivir and nirmatrelvir/ritonavir, remained effective against the different recombinant viruses. There are currently no reported cases of XEC in the Philippines, although with reduced testing it is possible that it just remains undetected. 

The US has continued to vaccinate with updated monovalent boosters annually since the bivalent vaccine was released in 2022. In 2023, the reformulated monovalent booster targeted XBB and did add some protection from infection for the circulating variants at that time. The US is currently gearing up for the launch of the latest monovalent booster based on KP.2, which was the dominant Omicron sublineage in June 2024. 

The US Centers for Disease Control (CDC) recommends that everyone six months and older should get an updated vaccine. However, this recommendation is not followed by the World Health Organization and most countries due to the relatively modest additional protection in the general population of an updated vaccine versus the added cost. While there is good evidence of added protection, especially for elderly and immunocompromised persons, the incremental benefit in other populations seems to be marginal at most. Should updated vaccines make it to the Philippines, I believe that the best targets for these should be healthcare workers, the elderly, and the immunocompromised. In the meantime, young children who were below the age of five prior to the rollout of the vaccines can get vaccinated with the new vaccines as a primary series. We hope that the FDA gives approval for the updated vaccines soon so that we can refresh the immunity of our most vulnerable populations and vaccinate the very young who have not had their primary series. In the meantime, these vulnerable populations and their families should judiciously use masks in crowded areas or when there is a higher risk of contracting infection.

Meanwhile, another country in Asia has reported a new case of mpox clade Ib. Aside from Thailand, India has now confirmed a case of the deadlier clade Ib strain of mpox in a 38-year-old male with recent travel to Dubai. The Indian government is doing contact tracing and quarantining close contacts. Since mpox is not airborne and has a longer incubation period (5-21 days) than Covid-19, there is a better chance of containment if public health measures are effectively implemented.

In the Philippines, the number of confirmed mpox cases for 2024 is now up to 23 cases as of this writing. All reported cases are clade II, which is considered milder, and more than half have recovered. Most cases are male and are relatively young. Clade II has likely continued to circulate locally since 2022 and transmission continues at a low level among susceptible populations. We have not yet reported any clade Ib infections, and surveillance continues especially among returning travelers.

If a clade Ib-infected person does manage to enter into the Philippines, the Department of Health will most likely reactivate the Interagency Task Force for Emerging Infectious Diseases (IATF-EID) to formulate and recommend policies for containment and mitigation of the new virus. Measures for clade Ib (but not for clade II) will include stringent isolation and quarantine in order to prevent community spread. Given the characteristics of transmission of mpox clade Ib, there is a good chance that we can stop it in its tracks if it ever arrives on our shores as long as scientific recommendations are followed and implemented. The most important step at this time is to ensure that we can detect the entry of clade Ib as early as possible to prevent it from gaining a foothold in the community. This will mean increasing testing capacity and simplifying the procedures to get a test for those who develop a rash that is suspicious for mpox.

If clade Ib does eventually make it into the community, there are many steps we can take to mitigate its effect. Good hand hygiene is essential in slowing down the spread of mpox, whatever the clade. Stringent enforcement of public health measures in spas and massage parlors where many cases of transmission were documented for clade II is another important measure. Guidelines already exist for decreasing the risk of infection in these public places. Safe sex practices are also important since both clades can be sexually transmitted. Finally, educating the public about infectious diseases in general, whether mpox, Covid-19, influenza, or other communicable diseases, goes a long way in decreasing the burden of these diseases on the Filipino people. No one wants to go back to the lockdowns and quarantines of the Covid-19 pandemic. If we stick to the lessons we learned from that dark period, we will be okay.