Chikungunya cases drop by 77 per cent

The Chikungunya outbreak affecting Samoa appears to be contained, with the number of reported cases down 77 per cent from the height of the epidemic.

In its latest health communiqué the Ministry of Health (M.O.H.) has reported that the number of cases presenting to authorities has been decreasing since early December, a trend that has continued into this month.

M.O.H. C.E.O. Dr. Leausa Take Naseri says since the outbreak began late July 2014, the estimated number of people reporting to clinics is more than 4,289.

“Which is approximately 2.3 per cent of the total Samoa population,” he said.

Looking at the weekly distribution on the outbreak (see Figure 1 above), it was week 10 into the outbreak when the Ministry began reporting a mostly steady increase in the number of cases that presented to health authorities.

This number peaked in the final week of November, week 18, when more than 330 people showed symptoms.

This past week has seen a 77 per cent decrease on this figure, with only 76 people presenting to authorities with symptoms.

Leausa says features of Chikungunya infection are symptoms of acute fever, joint pains and an itchy maculopapular rash.

A maculopapular rash is one that is characterised by a flat, red area on the skin that is covered with small, connected bumps.

“Severity of symptoms have varied from person to person as this infection is a new virus for the Samoa population,” he says.

“Generally, symptoms have been mild for many people and consequently many do not come to the hospital clinics.”

Leausa said symptoms, however, could be severe or persist for long periods of time, or even recur.

“When experiencing above symptoms, pain relief and rest is highly recommended,” he said.

“So far, no confirmed deaths due to Chikungunya infection have been reported.”

In an effort to keep the number of Chikungunya cases affecting Samoa down, Leausa and his Ministry recommend continual vigilance by everyone with an emphasis on source reduction.

“Clearing and destroying mosquito breeding grounds,” Leausa says.

“These are most commonly heavy containers that may provide stable waterlogged environments less likely to be disturbed for weeks on end, and are usually old tyres; old ceramic, plastic or metal containers that retain water, blocked gutters of houses and pot plants and many water retaining plants near houses or loggings.

“These need regular clearing to stop (the) mosquito life-cycle and effectively cut off production of adult mosquitoes.”

Leausa said that vector (mosquito) control was also continuing for targeted areas.

“These chemicals kill off adult mosquitoes - but it is not as effective as clearing breeding sites,” he said.

“As one adult female mosquito can produce hundreds and hundreds of eggs which become adult mosquitoes.”

Other prevention methods the Ministry recommends is that people dress appropriately to avoid mosquito bites especially early morning and late afternoon.

Also people can stop mosquitoes bites by the use of mosquito nets, coils, repellents, screens, insect sprays.

“(Moreover) nurse patients and highly at risk people such the elderly and infants, under mosquito nets,” Leausa advises. “(And) drain stagnant water inside and outside living quarters.”

Leausa says other ongoing activities included a multi-media campaign with health educational and promotional messages on awareness and source reduction.

“(Also) Multi-sectoral and stakeholder collaborations including Border Control activities,” he said.

“Weekly syndromic surveillance system for monitoring outbreak (and) on-going reports and updates (are continuing).

“(In addition to this a) vector surveillance work plan (is) in place for monitoring mosquito species in Samoa and future resistance studies.

“(And) Infrastructure and Systems review for strengthening Public Health work.”

Turning now to the surveillance data provided by the M.O.H., of the 4,289 cases that have presented with symptoms, 2,358 have been female and 1931 have been male with the 20-24 age group having the highest attack rate of 42.8 per 1,000 people.

The World Health Organisation (W.H.O) defines the attack rate as the proportion of the population who become ill after exposure to an illness.

“Approximately 2.3 per cent of the population have been affected,” Leausa says.

“The majority of ages affected continues to be those under 35 years old.”

“The most affected areas continue to be the densely populated Apia Urban Area (A.U.A.) and North West of Upolu (N.W.U.) region.

“Although most of Samoa, (both) Upolu and Savai’I, (is) affected, the highly affected areas so far are as follows (see Table 3 above), which are also the most densely populated areas.”

Leausa said for further information contact Ministry of Health on 68100.