Encephalitis adverse event reports that record this term

Kind of term: MedDRA preferred term

What a report is

A report is not proof that the drug was the cause of the event.

FDA says:

Adverse event reports submitted to FDA do not undergo extensive validation or verification. Therefore, a causal relationship cannot be established between product and reactions listed in a report. While a suspected relationship may exist, it is not medically validated and should not be the sole source of information for clinical decision making or other assumptions about the safety or efficacy of a product. Additionally, it is important to remember that adverse event reports represent a small percentage of total usage numbers of a product. Common products may have a higher number of adverse events due to the higher total number of people using the product.
Source: openFDA, Drug Adverse Event Overview, section "Responsible use of the data". The site read the page on 2 Oct 2026. The data have the reports that FDA received through 30 Jun 2026.

FDA also says:

There is no certainty that the reported event (adverse event or medication error) was actually due to the product. FDA does not require that a causal relationship between a product and event be proven, and reports do not always contain enough detail to properly evaluate an event. The information in these reports has not been scientifically or otherwise verified as to a cause and effect relationship and cannot be used to estimate the incidence of these events.
Source: openFDA, Drug Adverse Event Overview. The site read the page on 2 Oct 2026.

Do not rely on openFDA to make decisions regarding medical care. While we make every effort to ensure that data is accurate, you should assume all results are unvalidated.
Source: openFDA, Response of the drug event API (meta.disclaimer). The site read the page on 2 Oct 2026.

Not medical advice. This site counts what was reported to FDA. Questions about a medicine or device belong with a pharmacist or clinician.

Reports on file

From January 2004 to June 2026, FDA received 6,794 adverse event reports that record the MedDRA preferred term Encephalitis. The person who codes a report selects the term that agrees best with the description of the reporter.

FDA received 465 reports in the 12 months to June 2026 and 488 in the 12 months before. FDA releases FAERS data every quarter, so the newest months are not complete. They grow in later releases.

By reports in the 12 months to June 2026, this term was number 1,024 of 1,436 reaction terms with a page. Of the 1,332,454 drug reports that FDA received in the 12 months to June 2026, 465 (under 0.1%) record this term. Reports for male patients were 42% of the reports that record this term and 34.6% of all drug reports.

The number of people who use the product is not in the data. A count is not a rate.

MedDRA

The Medical Dictionary for Regulatory Activities. The person who codes a report selects the preferred term that agrees best with the description of the reporter. FDA does not publish the description.

Data version

openFDA FAERS release of 29 Oct 2026. Reports received through 30 Jun 2026.

Drugs in these reports

The table has the 102 drug pages with 25 or more reports that record this term. The rows are in order of name. A drug page with fewer reports for this term is not in the table. The counts are the counts that the site keeps for each reaction term, and a count can be lower than the count of FDA.

FDA says:

Additionally, it is important to remember that adverse event reports represent a small percentage of total usage numbers of a product. Common products may have a higher number of adverse events due to the higher total number of people using the product.
Source: openFDA, Drug Adverse Event Overview. The site read the page on 2 Oct 2026.

Importantly, the AEMS data by themselves are not an indicator of the safety profile of the drug or biologic.
Source: FDA, FDA Adverse Event Monitoring System (AEMS) Public Dashboard. Content current as of 11 Mar 2026. The site read the page on 2 Oct 2026.

Drugs that the reports with the term Encephalitis name as a suspect product, in order of name
Drug	Class	Reports with this term
Abatacept	Selective T cell costimulation modulator	28
Aciclovir		37
Actemra	Interleukin-6 receptor antagonist	83
Acyclovir	Herpes simplex virus nucleoside analog DNA polymerase inhibitor	84
Adalimumab	Tumor necrosis factor blocker	61
Alemtuzumab	CD52-directed cytolytic antibody	25
Amoxicillin	Penicillin-class antibacterial	60
Aripiprazole	Atypical antipsychotic	25
Asparaginase		45
Atezolizumab	Programmed death Receptor-1 blocking antibody	152
Avastin	Vascular endothelial growth factor inhibitor	63
Avonex	Interferon beta	38
Azathioprine	Purine antimetabolite	55
Bevacizumab	Vascular endothelial growth factor inhibitor	91
Bortezomib	Proteasome inhibitor	29
Busulfan	Alkylating drug	30
Carboplatin	Platinum-based drug	158
Ceftriaxone	Cephalosporin antibacterial	33
Ciclosporin		36
Cimzia	Tumor necrosis factor blocker	25
Cisplatin	Platinum-based drug	51
Clarithromycin	Macrolide antimicrobial	27
Clobazam	Benzodiazepine	27
Cyclophosphamide	Alkylating drug	274
Cyclosporine	Calcineurin inhibitor immunosuppressant	93
Cytarabine	Nucleoside metabolic inhibitor	159
Daunorubicin		34
Dexamethasone	Corticosteroid	222
Doxorubicin	Anthracycline topoisomerase inhibitor	55
Doxorubicin hydrochloride	Anthracycline topoisomerase inhibitor	49
Durvalumab	Programmed death Ligand-1 blocker	43
Enbrel	Tumor necrosis factor blocker	146
Etoposide	Topoisomerase inhibitor	124
Everolimus	Kinase inhibitor	41
Filgrastim	Leukocyte growth factor	38
Fluconazole	Azole antifungal	47
Fludarabine	Nucleoside metabolic inhibitor	116
Fludarabine phosphate	Nucleoside metabolic inhibitor	35
Folinic Acid		38
Gilenya	Sphingosine 1-phosphate receptor modulator	34
Human immunoglobulin g	Human immunoglobulin G	45
Humira		201
Hydrocortisone	Corticosteroid	68
Hydroxychloroquine	Antimalarial	71
Ibrutinib (form s4)	Kinase inhibitor	40
Ibuprofen	Nonsteroidal anti-inflammatory drug	86
Imfinzi	Programmed death Ligand-1 blocker	30
Infliximab	Tumor necrosis factor blocker	48
Ipilimumab	CTLA-4-directed blocking antibody	91
Isoniazid	Antimycobacterial	49
Keppra		43
Keytruda	Programmed death Receptor-1 blocking antibody	228
Lacosamide		33
Lamivudine	Hepatitis B virus nucleoside analog reverse transcriptase inhibitor	49
Lamotrigine	Anti-epileptic agent	29
Leflunomide	Antirheumatic agent	65
Lenvima	Kinase inhibitor	45
Levetiracetam		50
Lorazepam	Benzodiazepine	32
Mabthera		45
Melphalan	Alkylating drug	46
Mercaptopurine	Nucleoside metabolic inhibitor	59
Meropenem	Penem antibacterial	29
Metformin	Biguanide	26
Methotrexate	Folate analog metabolic inhibitor	396
Methotrexate sodium	Folate analog metabolic inhibitor	45
Methylprednisolone	Corticosteroid	135
Metronidazole	Nitroimidazole antimicrobial	33
Mycophenolate mofetil	Antimetabolite immunosuppressant	263
Mycophenolic acid	Antimetabolite immunosuppressant	51
Nivolumab	Programmed death Receptor-1 blocking antibody	197
Ocrevus	CD20-directed cytolytic antibody	71
Opdivo	Programmed death Receptor-1 blocking antibody	188
Orencia	Selective T cell costimulation modulator	35
Oxaliplatin	Platinum-based drug	27
Paclitaxel	Microtubule inhibitor	78
Pantoprazole	Proton pump inhibitor	28
Pembrolizumab	Programmed death Receptor-1 blocking antibody	141
Pemetrexed	Folate analog metabolic inhibitor	30
Phenytoin	Anti-epileptic agent	37
Prednisolone	Corticosteroid	221
Prednisone	Corticosteroid	418
Prograf	Calcineurin inhibitor immunosuppressant	35
Propofol	General anesthetic	25
Remicade	Tumor necrosis factor blocker	106
Rinvoq	Janus kinase inhibitor	29
Ritonavir	Cytochrome P450 3A inhibitor	25
Rituxan	CD20-directed cytolytic antibody	37
Rituximab	CD20-directed cytolytic antibody	276
Stelara	Interleukin-12 antagonist	26
Tacrolimus	Calcineurin inhibitor immunosuppressant	279
Tecentriq	Programmed death Receptor-1 blocking antibody	114
Tecfidera		50
Thiotepa	Alkylating drug	28
Tysabri	Integrin receptor antagonist	107
Valproic acid	Anti-epileptic agent	30
Vancomycin	Glycopeptide antibacterial	36
Vimpat		30
Vincristine		95
Vincristine sulfate	Vinca alkaloid	70
Yervoy	CTLA-4-directed blocking antibody	101
Zidovudine	Human immunodeficiency virus nucleoside analog reverse transcriptase inhibitor	25

The page of each drug has the count of each reaction term in its reaction lookup.

Drug classes in these reports

The table has the 43 pharmacologic classes with 50 or more reports that record this term. The rows are in order of name.

FDA says:

Additionally, it is important to remember that adverse event reports represent a small percentage of total usage numbers of a product. Common products may have a higher number of adverse events due to the higher total number of people using the product.
Source: openFDA, Drug Adverse Event Overview. The site read the page on 2 Oct 2026.

Importantly, the AEMS data by themselves are not an indicator of the safety profile of the drug or biologic.
Source: FDA, FDA Adverse Event Monitoring System (AEMS) Public Dashboard. Content current as of 11 Mar 2026. The site read the page on 2 Oct 2026.

Pharmacologic classes of the drugs that the reports with the term Encephalitis name, in order of name
Class	Reports with this term
Alkylating drug	431
Anthracycline topoisomerase inhibitor	130
Anti-epileptic agent	147
Antimalarial	96
Antimetabolite immunosuppressant	335
Antimycobacterial	66
Antirheumatic agent	83
Atypical antipsychotic	123
Azole antifungal	70
Benzodiazepine	93
Calcineurin inhibitor immunosuppressant	438
CD20-directed cytolytic antibody	430
Cephalosporin antibacterial	62
Corticosteroid	1,092
CTLA-4-directed blocking antibody	198
Cytochrome P450 3A inhibitor	52
Folate analog metabolic inhibitor	480
General anesthetic	66
Hepatitis B virus nucleoside analog reverse transcriptase inhibitor	71
Herpes simplex virus nucleoside analog DNA polymerase inhibitor	139
Human immunodeficiency virus nucleoside analog reverse transcriptase inhibitor	57
Human immunoglobulin G	83
Integrin receptor antagonist	129
Interleukin-6 receptor antagonist	107
Janus kinase inhibitor	61
Kinase inhibitor	289
Microtubule inhibitor	93
Nonsteroidal anti-inflammatory drug	140
Nucleoside metabolic inhibitor	428
Opioid agonist	99
Penicillin-class antibacterial	78
Platinum-based drug	236
Programmed death Ligand-1 blocker	91
Programmed death Receptor-1 blocking antibody	1,028
Proteasome inhibitor	59
Proton pump inhibitor	96
Purine antimetabolite	62
Selective T cell costimulation modulator	63
Thalidomide analog	53
Topoisomerase inhibitor	136
Tumor necrosis factor blocker	422
Vascular endothelial growth factor inhibitor	154
Vinca alkaloid	70

A class with many reports in all has many reports for almost every term.

Reports by month

Reports that record Encephalitis, by month, five years to June 2026

FDA releases FAERS data every quarter, so the newest months are not complete. They grow in later releases.

Patients in these reports

Age of the patient in the reports that record Encephalitis
Age	Reports	Share
Under 2	82	1.2%
2 to 11	363	5.3%
12 to 17	193	2.8%
18 to 44	1,083	15.9%
45 to 64	1,739	25.6%
65 to 74	889	13.1%
75 and over	579	8.5%
Age not given	1,866	27.5%

Sex of the patient in the reports that record Encephalitis
Sex	Reports	Share
Female	3,102	45.7%
Male	2,853	42%
Unknown or not given	839	12.3%

Age and sex are as the report gives them. 29% of these reports give the United States as the country.

Terms near this one

These are the next terms in the A to Z list. The links are for navigation.

Official pages

MedWatch Online Voluntary Reporting FormThe online form of FDA for a voluntary report.
MedWatch: The FDA Safety Information and Adverse Event Reporting ProgramThe page of the FDA program that receives reports about drugs and devices.
FDA Adverse Event Monitoring System (AEMS) Public DashboardThe public dashboard of FDA for adverse event reports on drugs and biologics.

The site checked these addresses on 2 Oct 2026. The links open in a new tab.

Cite this page

Reported Reactions. Encephalitis: adverse event reports that record this term. https://reportedreactions.com/reaction/encephalitis/ Source: U.S. Food and Drug Administration, openFDA Drug Adverse Event (FAERS) files, release of 29 Oct 2026. Reports received through 30 Jun 2026.

Where the data come from

The counts come from the openFDA Drug Adverse Event (FAERS) bulk files, release of 29 Oct 2026. The files have the reports that FDA received through 30 Jun 2026. A drug name is the name on the report. The site matches it to a brand name or a generic name of the National Drug Code Directory of 2 Nov 2026. A class is the pharmacologic class (EPC) of the FDA label.

The count has the reports with each spelling of one MedDRA preferred term. The site does not publish a report narrative, a lot number, a detail of a patient or the identity of a reporter. The record of FDA is the authority. See how the site counts reports, the data sources and the corrections page.

Questions

What does Encephalitis mean in an adverse event report?

It is a MedDRA preferred term. FDA codes the description of a reporter with the MedDRA dictionary. The openFDA files do not have the description itself, and this site does not show it.

Does a drug in the table mean that the drug was responsible for this reaction?

No. FDA says:

No individual drug is connected to any individual reaction.
Source: openFDA, Drug Adverse Event Overview. The site read the page on 2 Oct 2026.

When a report lists multiple drugs and multiple reactions, there is no way to conclude from the data therein that a given drug is responsible for a given reaction.
Source: openFDA, Drug Adverse Event Overview. The site read the page on 2 Oct 2026.

What does this page tell a person who has this symptom?

This page gives counts of reports. It cannot assess a person. A pharmacist or a clinician can assess a person.

If this is a medical emergency, please call 911.
Source: FDA, MedWatch Online Voluntary Reporting Form. The site read the page on 2 Oct 2026.

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