The weather is cold and damp now and many people are coughing and sneezing. The 200 known cold viruses and four types of human influenza are having a field day. Contrary to popular belief, you don’t catch a cold by getting wet in the rain or caught without warm clothes in the evening chill. These viruses spread through airborne droplets that are coughed and sneezed out. They can also settle on furniture and walls from where they are transferred once someone touches the contaminated surface. The cold virus can survive outside the body for seven days and the flu virus for one day.

The virus enters the body through the nose, reaches the back of the throat and, eventually, the lungs. It invades the cells lining these passages and forces them to make more viruses. The body tries to fight this invasion by making chemicals called interferons. As these attack the virus, fever, runny nose, cough and body ache appear. The symptoms are more severe with flu than with a common cold.

The body’s immunity system needs water to fight infection. Antibodies are transported in body fluids. Mucous traps the virus particles and expels them. Drinking hot fluids will help symptoms and immunity improve. Lemon and orange juice too help hydrate the body while providing vitamins, antioxidants and micronutrients.

A sore throat is eased by gargling with warm salt water. Steam inhalations liquefy the mucus, which can then be coughed out. As the sinuses open up, the headache gets better.

Antihistamines dry secretions. Cough suppressants prevent an irritating cough. Although these two make make you feel better, they will prolong the infection as they prevent expulsion of the viruses and secretions.

While rest is universally recommended for flu and colds, lying down is counterproductive. If you lie flat, the lungs cannot expand efficiently. Bacteria that have entered the respiratory tract and are in the mucous can enter the lungs, causing pneumonia. This could be fatal in older adults, pregnant women and young children. Other complications are bronchitis, sinusitis and ear infections.

Cold and flu viruses produce symptoms two to four days after they enter a body. During that time the infection spreads to all and sundry as there are no symptoms to warn people away. This is especially true in a closed environment such as an airconditioned office, mall or movie theatre.

It is not easy to prevent cold and flu. The viruses are highly infectious and spread before symptoms manifest.

• Cough or sneeze only into a tissue. If nothing is available, cough into your elbow.
• Wash hands frequently with soap and water or use a hand-sanitising liquid
• Avoid going to school or office till the running nose and fever have subsided. The cough may take much longer to disappear. Often, it is just irritating and not infectious.

In healthy people with the flu (but not the common cold) oseltamivir (Tamiflu) and its higher derivatives can reduce the severity and duration of infection if taken within 48 hours of symptoms appearing. The medication is expensive and has side effects such as nausea and vomiting.

The flu vaccine reduces the likelihood of infection and reduces the severity of symptoms as well as complications. The vaccine mutates, and immunity lasts just a year. The vaccine should be taken every year before the flu season, which is from October to March.

Children between six months and eight years of age require two doses of quadrivalent flu vaccine four weeks apart. Adults require a single yearly dose.

The writer is a paediatrician with a family practice at Vellore and the author of Staying Healthy in Modern India. If you have any questions on health issues, please write to yourhealthgm@yahoo.co.in