How much do you know about adenovirus infection?

Viral infections are very easy to spread in daily life and are more common among children. Its causes are mainly due to cultural characteristics, resistance, pathogenicity and immunity. Therefore, people can do a better job of prevention after understanding its causes. At the same time, they can participate in treatment in time when they find similar symptoms.

1. Etiology

Adenovirus is a DNA virus belonging to the Adenoviridae family. Because it can cause inflammation of the lymph nodes (glandular), pharynx and conjunctiva, it is also called adeno-pharyngeal-conjunctival virus (APC virus for short). Under electron microscope, it appears as icosahedral particles with a diameter of 70 to 80 nm. The core is composed of double-stranded DNA and protein, with a nucleocapsid on the outside and 252 capsomers on the top, composed of 240 hexons and 12 pentons. It has no lipid coating on the outside, so it can resist lipid solvents such as ether and chloroform. It is acid-resistant but heat-resistant. The virus can be inactivated at 56°C for 30 minutes. This virus can be isolated and propagated using cell cultures such as human embryonic kidney, monkey kidney, and human amniotic membrane. There are currently at least 35 different serotypes known. There is no cross-immunity between viruses of different serotypes. The most common pathogenic types are types 1 to 8.

2. Causes

1. Cultivation characteristics

There are no susceptible animals for human adenovirus and it cannot be grown in chicken embryos. However, it can proliferate in a variety of human-derived cell cultures and cause obvious CPE: the cells swell and become round, aggregate into grape-like clusters, and form alkali-tropic inclusion bodies in the infected cell nuclei.

2. Resistance

Adenovirus is highly resistant to physical and chemical factors, is acid-resistant, and can tolerate the effects of proteases and bile. It can survive for more than 10 days at room temperature and will be inactivated at 56℃ for 30 minutes.

3. Pathogenicity

Adenovirus invades the human body through the respiratory tract, digestive tract or conjunctiva, proliferates in local lymphoid tissues such as tonsils, proliferative glands, and mesenteric lymph nodes, and does not form viremia.

Adenovirus mainly infects children, and most cases are asymptomatic. The related clinical diseases are mainly acute pharyngitis in children, acute respiratory tract infection and viral pneumonia. Certain types of adenovirus can cause diarrhea in infants, called enteric adenoviruses. In addition, it can also lead to other clinical diseases, such as acute hemorrhagic cystitis in children.

Tissue damage caused by certain viral infections that is mediated by the body's immune response. For example, although respiratory syncytial virus causes minimal direct damage to ciliated respiratory epithelial cells, it can cause severe respiratory disease in infants and young children. It is worth noting that the age at which children are most susceptible to the disease is exactly the stage when the level of maternal antibodies is the highest. To determine whether it is related to the immune response, we can see whether the condition of naturally infected people worsens after vaccination. If so, then it is likely related.

Among them, adenovirus pneumonia is a common disease among children in northern my country, and there was an epidemic in 1958. Group A adenoviruses have the property of transforming cells in vitro and can cause cancer in newborn hamsters. However, there has been no report on its carcinogenicity in humans so far.

4. Immunity

After adenovirus infection, specific antibodies are produced, which have a protective effect against infection by the same type of virus and provide long-lasting immunity.

3. Clinical manifestations

Different serotypes of adenovirus cause different clinical manifestations, which can be divided into the following types:

①Acute upper respiratory tract infection. Symptoms include fever, clear runny nose, sore throat, cough, hoarseness, etc. Half of the cases developed white exudate in the throat and swollen cervical lymph nodes. The fever subsided and systemic symptoms were alleviated after 3 to 4 days, but respiratory symptoms such as cough may persist for 1 to 2 weeks.

②Adenovirus pneumonia. Mainly caused by types 3 and 7. It is more common in children and may occur secondary to measles. The lesions are patchy or confluent pneumonia, and the inflammation may extend to the entire lung lobe. The onset is acute, with symptoms such as fever, cough, shortness of breath, nasal fanning, chest pain, etc. Pleurisy may also occur. In severe cases, there will be breathing difficulties and cyanosis, and heart failure and even death may occur.

③Pharyngeal conjunctiva heat. The most common pathogen is type 3, but types 1, 2, 5, 6, 7, and 14 can also cause it. Often causes epidemics among children. The disease develops rapidly, with the main symptoms being fever, pharyngitis, unilateral or bilateral conjunctivitis and cervical lymphadenopathy. The course of the disease is about 5 days.

④Eye infection. It can manifest as follicular conjunctivitis, which is mainly caused by types 3 and 7. The conjunctiva is obviously congested and many follicles can be seen in the eyelid conjunctiva. It can also manifest as epidemic keratoconjunctivitis, which is mainly caused by types 8 and 19. Conjunctivitis occurs first, followed by keratitis. The course of the disease can last for several weeks to several months and can cause visual impairment. It is mostly prevalent among swimmers.

⑤Others. Symptoms of gastroenteritis such as vomiting, diarrhea, abdominal pain, etc. may occur. Adenovirus can be isolated from the feces. Hemorrhagic cystitis, mesenteric lymphadenitis, etc. may also occur. It can cause encephalitis and meningitis in organ transplant recipients and those with weakened immune systems.