Parainfluenza and Respirary syntical viruse
As any parents knows, a group of little kids at the playground will usually include gigglers, criers and coughers. With luck and forebearance, crying and coughing fade away as giggling is joined by whispering and shouting. Fortunately, we are concerned here with coughing because it is fast easier to explain than the rest of the din.
Bronchitis, bronchiolitis, croup and pneumonia ----- four mainstays of the pediatrician's trade ----- are brought primarily to young children by members of the paramy xoviridae family of viruses, others of which cause mumps and measles. These diseases are universal because the bugs are, too. They are highly infectious through personnal contact and need invade our bodies no deeper than our nose or throats to start replicating like crazy in the mucus there. The only way to avoid them would be to stop breathing. They strike early in life because they are out there. Most people grow partially immune to them which is why parents at the playground aren't hacking as much as the kids.
The influenza viruses ----- there are four types of medical interest ----- cause lower respirary diseases in kids and upper respiratory problems in adults ( most grown-ups have some immunity so the bugs are defeated before they can travel very deep ). They were first isolated in the mid-1950s from children with croup. The two types most closely associated with croup tend to strike tots under two in the autumn of the year, with the greatest number of cases in populous areas coming at two-year intervals. Boy seem to get croup more often than girls. The type associated with bronchiolitis and pneumonia works all year round, mostlr on babies under six months old with no preference for blue and pink. So far, attempts to develop vaccines, perhaps best administered to infants as a nasal aresol, have not met with much success.
The respiratory syncytial virus (RSV) was first found in a chimp with a cold. It is now recgonized as the prime agent of life-threatening diseases of the lower respiratory tract ( pneumonia, bronchiolitis ) in infants and children all over the world. It is so universal that all adults are believed to carry an antibody as do babies for the first few weeks of life until the resistance acquired from mother wears off. RSV is the only virus that causes pediatric epidermics of respiratory disease every winter in big cities. As with so many other ills, poor kids are most likely to suffer from serious infections, perhaps because affluence somehow helps delay exposure past the period of greatest vulnerability ( the first six months of life ) to an age when reactions are milder. Efforts to make a vaccine have been about as futile as those against the parainfluenza virus. The matter is complicated by the fact that an infant's defensive system againts RSV invaders is suppresed by RSV antibodies carried out of the womb, so that any vaccine would have finesse this obstacle at least until those antibodies decayed.
The capsid of herpesviruses is about 100nm in diameter, has cubical symmetry with 162 capsomers and is surroundered by an envelope. There is a space between the envelope and capsid that contains a number of viral enzymes and other proteins that assist in the replication process. The herpesviruses are fairly unstable. After being shed from the body, they become inactivated within hours at room temperature and are readily deatroyed by drying, soaps and disinfectants. The necleic acid is double-stranded (ds) DNA and the viruses multiply in the nucleus of the host cell. Replication of the viral genome is under the control of enzymes encoded on the viral DNA. These enzymes such as DNA polymerase , thymidine kinase and ribonucleotide reductase are different from those produced by human cells and are antiviral compounds used in treatment of herpesvirus infections.
Under certain conditions the viral DNA is able to integrate into the host cell DNA to establish a latent infection. This association of foreign DNA with the DNA of the host cells has provided theoretical evidence that herpseviruses may induce cancer. Some forms of cancer in lower animals are associated with these viruses and several lines of evidence associate herpseviruses, particullarly the Epstein-BArr virus with certain forms of cancer in humans. Women who have cervical herpes infection have a significatly greater incidence of cervical cancer than uninfected women.