The Centers for Disease Control and Prevention (CDC) is notifying clinicians, public health authorities, and the public about the risk of severe arboviral neuroinvasive disease among patients who are receiving B cell-depleting or B cell-modulating medications, particularly anti-CD20 monoclonal antibodies (mAbs). Accordingly, patients should protect themselves against the bites of mosquitoes and ticks, which can increase patients' risk of arboviral disease (1).
The reason of this warning is an upsurge of arboviral infections in the United States. In particular, the number of cases of West Nile Virus (WNV) infection is increasing. Thirty states have reported WNV cases so far in 2026. As of August 18, 222 cases of WNV have been reported and 156 cases were neuroinvasive. Historically, West Nile cases peak in August and September. So, more cases are expected to emerge. This is the highest number of WNV cases in the last 22 years (2).
The arthropod-borne viruses or arboviruses are RNA viruses that are transmitted by insect vectors. WNV is one of the most common arboviruses, which is transmitted by mosquitoes. It usually causes asymptomatic infection in humans but in a small number of human hosts (1%) can cause severe febrile and/or neuroinvasive disease manifested as meningitis, encephalitis or acute flaccid paralysis.
Arboviral neuroinvasive disease, including WNV infection can be particularly serious in people taking anti-CD20 therapies. Anti-CD20 monoclonal antibodies include rituximab, ocrelizumab, ofatumumab, ublituximab, obinutuzumab, and ibritumomab tiuxetan.
There are no approved treatments, prophylactic agents, or human vaccines to prevent WNV. Protective measures that can be used, include: using mosquito repellants, avoiding mosquito-infested areas, eliminate their breeding sites, wear long sleeved clothes in the evening when outsides, etc. WNV vector, Culex pipiens, is spread worldwide. In Europe, WNV is endemic, particularly in its southern, central and eastern parts. Therefore, this information from CDC is important and relevant for the European region.
Key Points:
- Anti-CD20 therapy, rituximab, ocrelizumab, WNV, arboviral infections
References:
- https://www.cdc.gov/han/php/notices/han00532.html
- https://www.cdc.gov/west-nile-virus/data-maps/current-year-data.html
Publish on behalf of the Scientific Panel on Infectious diseases