A

• Adenovirus: Virus capable of infecting the respiratory, gastrointestinal, ocular, and urinary tracts. Some serotypes are associated with outbreaks in collective environments such as daycare centers and schools. Transmission occurs through respiratory droplets, fecal–oral route, or contact with contaminated surfaces. Although it generally causes self-limiting illnesses, it can lead to severe conditions in immunocompromised individuals.

• Acute Respiratory Infections (ARI): Group of diseases with rapid onset and limited duration, which may be caused by viruses (such as respiratory syncytial virus (RSV), rhinovirus, adenovirus, parainfluenza (1, 2, 3, and 4), metapneumovirus) or bacteria. ARIs are among the main reasons for medical visits worldwide.

• Alert thresholds: In InfoGripe, alerts are issued in an escalating set of levels: Low Risk, Alert, Risk, and High Risk. Low Risk thresholds indicate that SARS incidence is occurring at relatively low and safe levels for the region. The Alert threshold signals activity above a moderate level, but still below the high-level threshold. The Risk and High Risk thresholds indicate that case numbers are at elevated and very elevated levels, respectively. It is important to note that this indicator reflects the current level of activity, not a projection for upcoming weeks.

C

• COVID-19: COVID-19 is an acute respiratory infection caused by the SARS-CoV-2 virus, potentially severe, highly transmissible, and globally distributed. Many severe cases develop into Severe Acute Respiratory Syndrome (SARS). It was the disease responsible for the unprecedented pandemic from 2020 to 2022, marked by a substantial number of hospitalizations and deaths.

• Contact tracing and monitoring: Identification of people who had close contact with confirmed cases, for symptom monitoring and possible testing.

E

• e-SUS Notifica: Electronic system for reporting suspected and confirmed cases of notifiable diseases, including COVID-19. It enables fast data entry and integration with other databases.

• Epidemics: A significant and unexpected increase in the number of cases of a disease in a region, surpassing expected levels.

• Epidemiological profile: Set of information describing who becomes ill, when, and where, enabling understanding of the dynamics of a disease in a given population.

• Epidemiological Surveillance: Set of continuous and systematic actions aimed at collecting, consolidating, analyzing, and interpreting data on health events to guide the formulation, implementation, and evaluation of prevention and control measures. Epidemiological surveillance enables early detection of changes in disease patterns, identification of outbreaks and epidemics, monitoring trends, and assessing the impact of interventions such as vaccination campaigns or containment measures. It is a cyclical and integrated process involving data collection, processing and consolidation, analysis and interpretation, dissemination of information, and implementation of public health actions. Epidemiological surveillance may be universal (covers all cases of a given disease throughout the territory), sentinel (based on selected health units representative of a territory or population); event-based or syndromic (focused on early detection of syndromes or unusual events, even before laboratory confirmation). In Brazil, epidemiological surveillance is integrated into the National Health Surveillance System and regulated by Ministry of Health standards, and is carried out by municipal, state, and federal health departments, in coordination with the World Health Organization (WHO) and other international networks.

H

• Health and Environment Surveillance Secretariat of the Ministry of Health (SVSA/MS): Federal government body responsible for coordinating national actions in epidemiological, environmental, and sanitary surveillance.

I

• Influenza: Influenza, or flu, is a viral respiratory infection caused by influenza viruses, leading to symptoms such as fever, cough, sore throat, and muscle aches. Severe cases may progress to Severe Acute Respiratory Syndrome (SARS).

• Influenza-like Illness (ILI): Clinical syndrome characterized by sudden onset of fever, even when self-reported, above 38°C, accompanied by cough or sore throat, with symptom onset in the last 7 days. It may include other symptoms such as headache, runny nose, and muscle pain. In epidemiological surveillance, it serves as an initial criterion for suspected infections caused by respiratory viruses, including influenza viruses and COVID-19.

• Influenza Epidemiological Surveillance Information System (Sivep-Gripe): Digital platform of the Ministry of Health used for recording, analyzing, and disseminating data on ILI and SARS, with restricted access to authorized professionals.

• Influenza Virus: Group of respiratory viruses classified into types A, B, and C (and type D, restricted to animals). Type A circulates in humans and various animal species, has high genetic mutation and reassortment capacity, and generates subtypes such as H1N1 and H3N2, with pandemic potential. Type B circulates almost exclusively in humans and causes seasonal epidemics. Type C causes milder and less frequent infections. Influenza viruses undergo gradual mutations and abrupt changes, requiring annual updates of the vaccine according to WHO recommendations.

• Influenza A (H1N1)pdm09 virus: Subtype of influenza A virus that emerged in 2009, resulting from genetic reassortment among swine, avian, and human influenza viruses. It caused the 2009–2010 pandemic, characterized by rapid global spread and significant impact on young adults and pregnant women. Since then, it has become one of the seasonal subtypes of influenza A, included in the annual vaccine formulations.

L

• Laboratory diagnosis: Use of laboratory techniques (e.g., RT-PCR, rapid tests, viral culture) to confirm the presence of pathogens in clinical samples.

M

• Metapneumovirus: Virus responsible for respiratory infections like those caused by RSV, with greater impact on young children, older adults, and immunosuppressed individuals. It is transmitted through respiratory droplets and direct contact. Its seasonal circulation can coincide with or overlap RSV and influenza seasons.

N

• Nowcasting: Based on historical patterns of reporting delays and the partial information available at the present moment, nowcasting models, such as those proposed by Bastos, Economou et al. (2019), use advanced statistical methods (often Bayesian) to estimate the “true total” number of cases or deaths up to the most recent date. In essence, nowcasting allows decision makers to have a more accurate and real-time understanding of the epidemiological situation, even with incomplete data, improving situational awareness and enabling more timely and effective public health actions.

• National Health Surveillance System: Integrated structure of agencies, institutions, and services at all levels of government responsible for monitoring and controlling health risks and disease burden in the population.

O

• Outbreaks: Sudden occurrence of disease cases above the expected level in a restricted area or specific population group.

P

• Pandemic: Large-scale epidemics with global spread and significant impact on health, economy, and society.

• Parainfluenza (1, 2, 3, and 4): Viruses that are important causes of laryngotracheitis (croup), bronchiolitis, and pneumonia, especially in children. Type 3 is the one most associated with severe infections in infants. Transmission occurs through droplets and direct contact with respiratory secretions.

• Pathogenicity: The ability of an infectious agent, such as a respiratory virus, to cause disease after infecting a host.

R

• Risk factors: Characteristics or exposures that increase the likelihood of developing a disease, including pre-existing health conditions and risk behaviors.

• Risk groups: Segments of the population that are more vulnerable to developing severe forms of a disease, such as older adults, children, pregnant women, and immunosuppressed individuals, in the case of SARS (Severe Acute Respiratory Syndrome).

• Respiratory Virus Surveillance Network: Set of structures and procedures designed to identify and monitor the circulation of respiratory viruses of public health importance, supporting prevention and control actions. It plays a fundamental role in early detection of outbreaks, identification of seasonal circulation patterns, monitoring genetic and antigenic changes in circulating viruses, and assessing the impact of prevention measures such as vaccination and antivirals. It also contributes through regular submission of viral isolates to World Health Organization (WHO) collaborating centers, supporting the global influenza surveillance system and the annual selection of strains included in the influenza vaccine.

• Reporting of suspected cases: Entering clinical, epidemiological, and laboratory information into official surveillance systems.

• Rhinovirus: The main cause of the common cold. It has more than 150 known serotypes, which makes vaccine development difficult. Infection is usually mild but can worsen chronic respiratory diseases such as asthma and COPD, especially in vulnerable populations.

• Respiratory Syncytial Virus (RSV): Virus responsible for one of the main causes of bronchiolitis and pneumonia in infants, young children, and older adults. It is transmitted through respiratory droplets and direct contact. It has two main subgroups (A and B) and represents a major public health challenge due to high rates of pediatric hospitalization and the absence, until recently, of a widely available vaccine.

S

• Seasonal pattern: Predictable trends of increase or decrease in the incidence of a disease during specific periods of the year, such as the winter months.

• Suspected case notification: The act of officially reporting a possible case of a particular disease, even before laboratory confirmation.

• SARS-CoV-2: Etiologic agent of COVID-19. It has high transmissibility and the ability to generate variants with different degrees of severity and immune escape. Transmission occurs through droplets, aerosols, and contact with contaminated surfaces, causing clinical presentations ranging from asymptomatic infection to severe acute respiratory syndrome and death.

• Severe Acute Respiratory Syndrome (SARS): A more severe progression of an influenza-like illness, which can rapidly evolve into respiratory failure. It is defined as an individual with influenza-like illness who presents shortness of breath / respiratory discomfort OR persistent chest pressure OR oxygen saturation ≤ 94% on room air OR bluish discoloration of lips or face.

T

• Trend indicator: The current trend indicator for SARS cases used in InfoGripe is an estimate based on the variation pattern in the number of new weekly cases over the past 6 (six) weeks for the long term. That is, if there has been, on average, an increase in new cases during the last 6 (six) weeks, the long-term indicator will show a growing trend for the current week. As with the SARS activity indicator, it is important to highlight that the trend indicator refers to the current week and is not a projection for the next 6 weeks. Because it is a statistical assessment, the trend is presented in terms of the probability that an increase or decrease is occurring. When these probabilities are below 75% in either direction, this indicates stabilization or oscillation without significant increase or decrease during the period in question.

W

• World Health Organization (WHO): United Nations agency responsible for coordinating international health actions, issuing technical recommendations, and supporting countries in responding to health crises.