The US Centers for Disease Control and Prevention (CDC) reported yesterday that the rise in measles cases so far this year is mostly imported, due to infected people coming into the US from other countries.

For the seven years up to 2007, an average of 62 cases of measles a year have been reported to the CDC. But this year, up to 25th April, a total of 64 cases, 54 of which are imported from countries outside the US, have been reported. This is the highest number for this time of year since 2001, said the agency. 63 of the 64 patients had not been vaccinated.

Measles is described by the World Health Organization (WHO) as one of the best known and “most deadly of all childhood rash/fever illnesses”.

It is a highly contagious, acute, vaccine-preventable, viral disease that can lead to serious complications and death. It is spread by droplets or direct contact with nasal or throat secretions from infected people, and less commonly by touching anything they may have soiled.

A successful vaccination campaign in the US has virtually eradicated the disease, to the point where measles elimination was declared in the country in 2000. In the World Health Organization (WHO) region of the Americas measles elimination was declared in 2002. Elimination is defined as the “interruption of endemic measles transmission”.

Meanwhile, however, the situation in many other parts of the world is not so good, where the total number of cases each year is thought to be around 20 million.

The CDC said that although the disease has been virtually eliminated in the US, it can still be imported, and the surge in cases this year serves to remind all Americans of the importance of maintaining a high rate of vaccination in the population.

According to the agency, before measles vaccination was introduced in the US in 1963, every year about 3 to 4 million Americans caught measles, around 400 to 500 died of the disease, 48,000 were hospitalized, and 1,000 became chronically disabled from measles encephalitis.

Africa was held up by the WHO late last year as an example of what can be achieved in the developing world by a rigourous vaccination campaign. The United Nations goal to cut measles deaths in Africa by 90 per cent was reached 4 years early. Measles deaths in Africa fell by a spectacular 91 per cent between 2000 and 2006, from around 396,000 to 36,000. This success has helped to generate a strong decline in global measles deaths, said the WHO, which fell 68 per cent worldwide, from around 757,000 to 242,000 over the same period.

WHO Director-General Dr Margaret Chan paid tribute to Africa’s success, and urged other countries, such as India and Pakistan, with high numbers of measles deaths, to fully implement control strategies. About 74 per cent of measles deaths globally occur in South Asia.

According to a report in the New York Times, there is a growing number of parents in the US and other countries refusing to vaccinate their children against measles because of unproven fears about the vaccine causing autism and other illnesses. Health officials say this trend is responsible for the resurgence of measles in many developed regions like Israel, Austria, Ireland, Britain and Switzerland, where recent outbreaks have been linked to groups of people who refuse the vaccination.

Americans travelling abroad with children who have not been immunized need to be careful because they are more likely to come into contact with infected people in countries where measles has not been eliminated. Babies are usually immunized at 1 year old, but they can be immunized at 6 months as an added precaution, for instance if travelling out of the country.

The Times also reported a case of a baby in the US being infected while waiting in the clinic to receive the measles shot. Because the disease is now so rare, doctors and nurses don’t know the signs to look out for when infected patients come into the surgery. Anyone suspected of having measles should not sit in the waiting room with other patients, especially young babies.

Click here to read the full CDC report on measles cases in the US this year.

Sources: CDC, WHO, New York Times.

Written by: Catharine Paddock, PhD