Notes on Transmission, Protection and Prevention of Smallpox

Definition:

Smallpox is an acute highly communicable disease caused by vanilla virus. It is clinically characterized by a sudden onset of fever and severe body ache. On the third day of illness, there is an outburst of a typical rash which is abundant on the face, hands, legs and less on the covered parts of the body. It passes through many stages till the crusts fall off in about three weeks leaving behind Pock-marks which are permanent.

Mode of Transmission:

(i) Droplet Infection:

Transmission occurs predomi­nantly by droplet infection. The virus is expelled in droplets from the nose and mouth during coughing sneezing and talking. The infected particles are inhaled by people close to the patient.

(ii) Droplet Dust:

Transmission may also take place through the droplet dusts from infected clothing and adding the infected dust when inhaled causes the disease.

(iii) Air borne Transmission; Aerial spread of virus also occurs. The great dilution of virus in air when exposed, to sunlight makes airborne dissemination beyond the immediate environment of the patient.

(iv) Fomites: Transmission may take place indirectly, by articles used by the patient, e. g. infected clothing and bedding.

Incubation Period:

The incubation is fairly constant at 11 to 14 days but occasionally it may vary from 8 to 17 days.

Clinical Features:

Smallpox runs its course in two main stages;

(i) Pre-emotive Stage:

I he onset is generally acute the first symptoms are usually high fever, severe backache headache and pain all over the body. In children, there may be vomiting, delirium and convulsions this stage lasts for 2 to 4 days.

(ii) Eruptive Stage:

The main clinical manifestations of smallpox is the appearance of a rash over the body which shows certain distinctive features which are as follows ;

(a) Day of appearance:

The rash appears on the third or the fourth day illness.

(b) Distribution:

The rash is noticed first on face and upper part of the body. But within a day or two it appears also on the lower part of the body. In severe cases, the rash my cover the whole body.

(c) Development:

First of all the rash consists of maculae’s. These are bright red spots, 2-3 mm. in size and not rose above the surface of the skin. Within a day, they develop into papu­les raised above the surface of the skin. Clear fluids appear in the papules which become larger—vesicles. By the 4th or 5th day, pus is formed in the vesicles. They gradually dry up and dark scabs are formed over each. The scabs fall off during the next one or two weeks leaving behind the pitted pock marks on the skin.

Protection:

Vaccination undoubtedly protects the individual against small pox, at least for some time. The World Health Organization recommends the vaccination be repeated at 3 years interval for optimal protection Vaccination consists of introduction of sufficient amounts of vaccine virus or cow pox virus in to the skin and produce a local reaction. When this is done on a person not previously successfully vaccinated, it is called Primary Vaccination. When this is done on a person who has a vaccination scar, it is called Revaccination.

Time of Vaccination:

In India, primary vaccination is recommended soon after birth and to be repeated before the end of one year which provides an effective booster. The W.H.O. favors revaccination at intervals of 3 years. So, at the time of admission in to the school, the teacher should notice the scar mark of vaccination and if the child is not vaccinated he should inform the Public Health Department, as soon as possible.

Prevention of Small Pox:

The appearance of Small Pox in a community calls for urgent energetic measures to keep under control. These may be stated as follows:

(i) Early Diagnosis:

The first step in the control of Smallpox is early and accurate diagnosis of cases. When the number of cases is large, it is easy to diagnose but when the cases are few, every suspect case should be examined properly by doctors.

(ii) Notification:

Small Pox is a modifiable disease- locally nationally and internationally.

(a) Local: The disease must be reported immediate­ly to the local health authority. The Medical Officer of Health or Civil Surgeon who sends report by telegram, to the State Director of Health Services. The Collector of the District should be informed early.

(b) National: Report is also to be sent by telegram to the Director General of Health Services, Ministry of Health. Government of India, New Delhi.

(c) International: Under the International Health Regulations, countries have a duty to notify the W. H. O. in Geneva within 24 hours when a Small Pox case occurs in their territory.

(iii) Isolation:

Cases should be transferred to a smallpox hospital, if facilities are available. Where this is not possible, accommodation may have to be arranged in houses. Patients should be cared for by persons immune to the disease by recent or previous vaccination. Visitors should be restricted to a minimum and limited to those who are immune. The patient should be isolated until all scabs are separated.

(iv) Contacts:

Since transmission occurs primarily from close contact in the house, school or hospital all contacts of the patients should be sought out and vaccinat­ed. If any contact becomes sick, he should be promptly isolated.

(v) Mass Vaccination:

The entire population of the affected area should be systematically vaccinated in the shortest possible time, regardless of past history of vaccination. To impede the spread and to reduce the incidence of the disease to a low level, mass vaccination should also be undertaken in the neighboring villages and towns.

(vi) Disinfection:

(a) Nose and throat discharges should be disposed of by burning;

(b) Clothes and linen should be boiled or steam- sterilized;

(c) Disinfection of room should be done by fumiga­tion with formaldehyde vapor for 6 hours. The room may also be washed with soap water and should be exposed to direct sunlight for several hours;

(vii) Quarantine:

Under the Inter-national Health Regulations, a traveler who comes from or has passed through an infected area should have a valid Smallpox vaccination certificate or be vaccinated on arrival and be kept under medical supervision. If the person is not vaccin­ated or refuses to be vaccinated, the health-officer has the right to put him in quarantine for a period up to 14 days beginning from the time the person left the infected area.

(viii) Health Education:

Health education is an essen­tial part of a smallpox eradication campaign to enlist the co-operation of the people and local leaders in matters of early notification of cases and vaccination.