The infection spread through the air

Infections that can be transmitted through the air are often further categorized based on the mode of spread, specifically aerosol or droplet transmission. These categories are determined by the size of the respiratory particles carrying the infectious agents, their transmission distance, and the manner in which they are transmitted. Aerosol spread involves the transmission of infectious agents through small respiratory particles referred to as aerosols. These aerosols are typically less than 5 micrometers in diameter and have the ability to remain suspended in the air for extended periods. Consequently, they can travel considerable distances, surpassing the recommended social distancing measures of 1-2 meters. Examples of diseases commonly transmitted through aerosol spread include tuberculosis (TB), measles, chickenpox, and certain strains of influenza. These infections are highly contagious, as individuals can acquire them by inhaling the infectious aerosols released during coughing, sneezing, talking, or even normal breathing. The risk of aerosol transmission is particularly elevated in enclosed indoor spaces with inadequate ventilation, as the concentration of infectious particles can increase.

On the other hand, droplet spread entails the transmission of infectious agents through larger respiratory droplets. These droplets are typically generated when an infected individual coughs, sneezes, talks, or exhales forcefully. Unlike aerosols, droplets are larger in size, ranging from 5 to 10 micrometers in diameter, and tend to quickly fall to the ground or nearby surfaces within a short distance (around a meter or two). Infections commonly transmitted through droplet spread include respiratory illnesses such as the common cold, influenza, and COVID-19. These diseases are generally less contagious compared to those transmitted through aerosols since the droplets do not remain suspended in the air for extended periods. Close proximity to an infected person is usually necessary for the inhalation of respiratory droplets or for direct contact with mucous membranes like the eyes, nose, or mouth. However, it is important to acknowledge that the line between aerosol and droplet transmission is often not clearly delineated. Some infections have the potential to spread through both routes, and the actual transmission mechanisms can vary depending on factors such as the proximity of an individual to an infected person, environmental conditions, and the viral load present in the droplets or aerosols.

A. Tuberculosis

Tuberculosis (TB) infection manifests through various symptoms and signs, which can differ depending on the stage of the disease. In the latent TB infection (LTBI) stage, individuals typically do not exhibit any symptoms or signs. They may not feel sick as the TB bacteria are in an inactive state within their bodies. Traditional diagnostic tests, such as chest X-rays and sputum tests, are often negative during this stage. During the primary TB infection stage, individuals may experience a range of symptoms. These can include fever, fatigue, weakness, loss of appetite, weight loss, night sweats, and a persistent cough that lasts for more than three weeks. Other symptoms may consist of chest pain while breathing or coughing, coughing up blood (hemoptysis), swollen or tender lymph nodes, headaches, shortness of breath, and chills. In the secondary or reactivation TB stage, symptoms often become more pronounced. Individuals with this stage of the disease may exhibit chronic cough with sputum production, continued weight loss, persistent fatigue and weakness, fever, night sweats, loss of appetite, chest pain, and hemoptysis (coughing up blood).

The primary modes of transmission for tuberculosis (TB) are airborne transmission and direct transmission. Airborne transmission occurs when a person with active TB releases infectious droplets containing Mycobacterium tuberculosis through coughing or sneezing, which can then be inhaled by others. Direct transmission, on the other hand, refers to the transfer of TB from an infected individual to a close contact through prolonged and frequent exposure, usually in household or community settings. 

To prevent or minimize TB transmission in different settings, various strategies can be implemented. In healthcare facilities, it is crucial to establish proper infection control measures. This includes isolating patients suspected or confirmed to have TB in negative pressure rooms, ensuring adequate ventilation, providing healthcare workers with N95 masks, and promoting respiratory hygiene and cough etiquette. By implementing these measures, the risk of TB transmission within healthcare facilities can be significantly reduced. In households, individuals with active TB should take precautions to separate themselves from others, particularly by staying in well-ventilated rooms with open windows. They should also cover their mouth and nose while coughing or sneezing, utilizing tissues or masks to minimize the release of infectious droplets. Good household ventilation and regular cleaning can further contribute to reducing the risk of transmission within the household setting. Within communities, raising awareness about TB and its symptoms plays a crucial role. Encouraging individuals to seek early diagnosis and treatment when experiencing symptoms can help identify active TB cases earlier, limiting their potential to transmit the infection further. Promoting proper cough etiquette, respiratory hygiene, and the use of masks in crowded or enclosed places can also contribute to reducing TB transmission on a community level. Additionally, improving healthcare facilities in the community and ensuring access to diagnostic tests and treatment are vital components in reducing TB transmission. 

To specifically address direct transmission of TB within healthcare facilities, rapid identification, isolation, and treatment of individuals with active TB are essential. Healthcare workers should undergo regular screening for TB and be vaccinated with the Bacillus Calmette-Guérin (BCG) vaccine to enhance their protection. Appropriate use of personal protective equipment, such as masks, further reduces the risk of transmission among healthcare workers. In households where direct transmission is a concern, early identification and treatment of individuals with TB are crucial to decreasing the infectious period and therefore minimizing the risk of transmission within the household. Furthermore, household contacts of TB patients should be screened for latent TB infection and offered preventive treatment to reduce the risk of developing active TB.

The development of antibiotic resistance in tuberculosis (TB) is attributed to various factors, including characteristics of the Mycobacterium tuberculosis bacteria and inadequate use of antibiotics. The bacteria can acquire spontaneous mutations in their genetic material, leading to resistance to specific antibiotics. Moreover, inadequate treatment practices, such as improper drug selection, poor adherence to treatment regimens, and premature treatment discontinuation, contribute to the development of resistance. Additionally, the transmission of drug-resistant strains from one individual to another can further increase the prevalence of resistance in the community.

In order to combat the challenge of antibiotic resistance in the treatment of TB, several strategies can be employed. Firstly, conducting drug susceptibility testing prior to treatment initiation is crucial for determining the sensitivity of the infecting bacteria to specific drugs. This enables healthcare providers to select the most effective antibiotics and avoid the use of ineffective ones. Secondly, combination therapy, involving the use of multiple antibiotics simultaneously, can help prevent the development of resistance. By targeting different pathways, it becomes more difficult for the bacteria to develop resistance against all drugs simultaneously.

Furthermore, the implementation of the Directly Observed Treatment, Short-Course (DOTS) strategy can enhance treatment adherence and combat resistance. Under DOTS, patients receive their medication under the direct observation of healthcare providers or trained community workers, ensuring that the full course of treatment is completed. This strategy has been shown to improve treatment outcomes and reduce the risk of resistance development. Improved diagnostics for drug-resistant TB are essential to combating resistance effectively. The development and usage of rapid and accurate diagnostic tests enable healthcare providers to detect resistance at an early stage and tailor treatment accordingly. Early detection can facilitate the selection of appropriate antibiotics and prevent the further proliferation of drug-resistant strains.

To address the challenge of drug-resistant TB, the development of new drugs and treatment regimens is imperative. Research and development efforts focused on discovering new drugs that are effective against drug-resistant strains provide additional options for tailored treatment. These innovations can contribute to improved outcomes for patients with resistant TB. Moreover, infection prevention and control measures play a crucial role in combating TB resistance. Practices such as proper ventilation systems, the isolation of infected individuals, and comprehensive infection control strategies can reduce the transmission and acquisition of drug-resistant strains. By implementing these measures, the spread of resistant bacteria can be limited, thereby reducing the overall burden of drug-resistant TB.

B. Influenza:

The transmission and spread of influenza as an infectious disease are influenced by various key factors. Person-to-person transmission plays a crucial role, primarily occurring through respiratory droplets expelled when an infected individual coughs, sneezes, or talks. Additionally, international travel facilitates the rapid transportation of the virus across borders, contributing to its global dissemination. Crowded environments, such as schools, offices, public transportation, and healthcare facilities, provide optimal conditions for virus transmission due to the close proximity between individuals. Furthermore, the influenza virus exhibits the ability to survive on surfaces for a limited time, increasing the likelihood of indirect contact transmission.

The current strategies and interventions employed for the control and prevention of influenza transmission encompass several approaches. Vaccination plays a pivotal role in reducing the severity and spread of the disease, with annual flu vaccines specifically formulated to target prevalent strains expected to circulate. Another strategy involves the administration of antiviral medications, such as oseltamivir and zanamivir, which can diminish the duration and severity of influenza if initiated within the initial 48 hours of symptom onset. Public health campaigns are critical in increasing public awareness and adherence to preventive measures, including proper hand hygiene, cough etiquette, and staying home when experiencing symptoms. Moreover, social distancing measures, such as school closures, cancellation of mass gatherings, and promotion of remote work, aid in mitigating the spread of the virus. Surveillance systems and early warning mechanisms contribute to the timely detection and monitoring of influenza outbreaks, facilitating prompt public health responses.

The evolution and antigenic variability of the influenza virus pose significant challenges for the development of effective vaccines and antiviral drugs. The influenza virus undergoes constant changes through two primary mechanisms: antigenic drift and antigenic shift. Antigenic drift refers to gradual genetic alterations in the virus over time. These changes in surface proteins, hemagglutinin and neuraminidase, render the virus less recognizable to the immune system, thereby reducing the effectiveness of vaccines developed for previous strains. Conversely, an antigenic shift occurs when a major genetic recombination event results in the emergence of a novel influenza virus subtype. This phenomenon can occur when different strains of the virus infect the same host concurrently, such as humans and animals. An antigenic shift can potentially lead to pandemics if the population possesses insufficient or no pre-existing immunity.

Addressing the challenges posed by the evolution and antigenic variability of the influenza virus necessitates ongoing efforts in the development of effective preventive measures. Vaccine formulations are adjusted annually to incorporate the most recent strains prevalent in circulation, guided by surveillance systems that continuously monitor circulating strains. Antiviral drugs, primarily targeting conserved regions of the virus, such as neuraminidase, are designed to maintain effectiveness against diverse strains. However, to accommodate the constantly evolving nature of the influenza virus, continuous monitoring, research, and adaptation are imperative for the development of vaccines and antiviral drugs that remain efficacious against new viral variants. 

Written by D. M. C. V (Chloe Vo)