Lower Respiratory Tract Infections

B. pertussis is a strictly human pathogen, meaning that it only infects humans and does not infect other animals. This is supported by scientific evidence and research studies that have shown that B. pertussis does not have the ability to infect or cause disease in other species. This specificity to humans is one of the reasons why pertussis, also known as whooping cough, is primarily a human disease and not commonly seen in other animals.

Option A is the correct answer because it is the only option that completes the sentence correctly. The word "virulence" refers to the severity or harmfulness of a disease, and the word "epidemic" refers to the rapid spread of a disease within a population. Therefore, option A, which completes the sentence as "Influenza A has the greatest virulence and epidemic spread," suggests that influenza A is the strain of influenza that is most severe and spreads rapidly.

Direct droplet spread is the most common mode of transmission for the influenza virus. When an infected person coughs, sneezes, or talks, respiratory droplets containing the virus are produced and can be inhaled by others nearby. These droplets can travel a short distance and can be inhaled directly into the respiratory system of another person, leading to infection. This mode of transmission is particularly effective in crowded places or close contact situations, making it a primary route for the spread of the influenza virus.

The statement is explaining that the influenza virus does not cause any significant gastrointestinal involvement. In other words, it means that the flu virus primarily affects the respiratory system and does not typically cause severe symptoms or complications in the gastrointestinal tract. This is why the correct answer is "True."

Antigenic drift refers to a slower process of viral mutation in the RNA of influenza A, occurring every few years. It can result in as little as a single mutation. This process is responsible for the gradual changes in the surface proteins of the influenza virus, allowing it to evade the immune system and potentially leading to the need for updated vaccines each year. Unlike antigenic shift, which involves a major genetic change in the virus, antigenic drift involves small genetic changes that accumulate over time. The concept of the bottleneck effect is unrelated to this process.

Tuberculosis and AIDS are the leading causes of premature death in the world. Tuberculosis is a highly contagious bacterial infection that primarily affects the lungs and can be fatal if left untreated. AIDS, on the other hand, is caused by the HIV virus and weakens the immune system, making individuals more susceptible to various infections and diseases. Both tuberculosis and AIDS have a significant impact on global mortality rates, particularly in developing countries with limited access to healthcare resources.

Hemagglutinin is the correct answer because it is a glycoprotein found on the surface of influenza viruses. It plays a crucial role in viral attachment to host cells by binding to sialic acid receptors on the cell surface. Hemagglutinin is responsible for the initial step of viral infection, allowing the virus to enter the host cell and initiate replication. There are 15 recognized subtypes of hemagglutinin, each with different binding specificities and abilities to infect different species.

The correct answer is Th1 immune, DTH. The Th1 immune response is characterized by the activation of T-helper cells that release cytokines to stimulate the immune system to fight against intracellular pathogens. DTH (Delayed-Type Hypersensitivity) is a type of immune response that occurs hours to days after exposure to an antigen, resulting in the formation of granulomas. Therefore, the mixture of Th1 immune and DTH responses can lead to the formation of granulomas.

Influenza can cause death by exacerbating underlying diseases. When a person already has a weakened immune system or pre-existing health conditions, such as heart disease or respiratory disorders, the influenza virus can further compromise their health and lead to severe complications or even death. In such cases, the underlying disease acts as a contributing factor in the fatal outcome.

The H1N1 receptors are predominantly found in the upper portion of the respiratory tract. This is because the H1N1 virus primarily infects the respiratory system, particularly the nose, throat, and bronchi. By binding to the receptors in the upper respiratory tract, the virus can enter the body and cause respiratory symptoms such as coughing, sneezing, and sore throat.

Influenza A and B have 8 segments of negative-sense, single stranded RNA, while Influenza C has 7 segments.

Whooping cough is most communicable during the catarrhal phase. This phase is characterized by symptoms similar to the common cold, such as a runny nose, sneezing, and a mild cough. During this phase, the bacteria that cause whooping cough are present in the respiratory secretions and can easily spread from person to person through coughing or sneezing. The paroxysmal phase, on the other hand, is characterized by severe coughing fits and is less contagious. The convalescent phase is the recovery phase, during which the symptoms gradually improve and the person becomes less contagious.

Purified protein derivative (PPD) is used for skin testing of exposure to Mycobacterium tuberculosis (MTB). PPD is a substance derived from the tuberculin protein, which is extracted from the bacteria that cause tuberculosis. When injected into the skin, PPD elicits an immune response in individuals who have been exposed to MTB. This response is measured by the size of the resulting skin reaction, indicating whether the person has been exposed to the bacteria or not. PPD is a widely used diagnostic tool for tuberculosis and helps identify individuals who may require further testing or treatment.

Avian influenza viruses (H5N1) can retain infectivity for several weeks outside the host. This means that the virus can remain viable and capable of causing infection for an extended period of time when not in a host organism. This information is important in understanding the potential for the virus to spread and the need for proper disinfection and biosecurity measures to prevent its transmission.

Primary tuberculosis occurs when inhaled droplet nuclei are deposited in the peripheral respiratory alveoli. The question is asking which lobe(s) of the lungs are most frequently affected. The correct answer is "middle and lower" lobes. This means that the middle and lower lobes of the lungs are more commonly affected by primary tuberculosis compared to the upper lobe.

MTB (Mycobacterium tuberculosis) is known for its ability to produce large quantities of niacin, which is uncommon to other mycobacteria. Niacin is an essential vitamin that plays a crucial role in various metabolic processes. The production of niacin by MTB is one of its distinguishing characteristics and can be used as a diagnostic test to differentiate it from other mycobacteria. This unique ability of MTB to produce niacin sets it apart from other mycobacterial species.

Whooping cough is a prolonged illness caused by toxins produced by Bordetella pertussis bacteria.