Five more cases of Zika virus (ZIKV) infection surfaced in Kerala’s capital district on Thursday, taking the total number of cases reported so far in the State to 28.
All lab-confirmed cases of ZIKV in the State have so far been reported from Thiruvananthapuram alone.
The initial cluster of cases had been reported from within a private hospital at Anayara in the city and within the 3-km radius of the institution. But now, with more new cases being reported from scattered urban locations in the district, Health Minister Veena George has called for an urgent review meeting later on Thursday to assess the situation.
From across city
Of the five new cases reported on Thursday, which were confirmed at the National Institute of Virology’s Alappuzha unit, two are from within the Anayara cluster, while three cases have been confirmed from Kunnukuzhi, Pattom and East Fort, far outside the cluster.
On Tuesday, another case, totally unlinked to the cluster was reported from Sasthamangalam in a 41-year-old pregnant woman who has no travel history.
More cases likely
More new cases should be expected from across the district, especially in the urban areas, as clinicians are now beginning to send samples of patients reporting with fever and rashes, but who tested negative for both dengue and chikungunya (CHK), to labs.
The district health administration had earlier confirmed that fever with rashes, most of which had tested negative for dengue and CHK, were being reported from the district for the past four or five months. However, none had thought about linking it to ZIKV. Moreover, the district did not have facilities for performing the RT-PCR test for ZIKV till now.
It was only after a bunch of health-care workers working in the private hospital at Anayara reported fever with rashes (apart from several patients who came to outpatient clinics) that the Infectious Department there decided to send samples to a Coimbatore-based lab for testing.
The first lab-confirmed case of ZIKV in the State was thus reported first from the Coimbatore lab, which was later confirmed at NIV, Pune. Following this the State has now equipped the Microbiology labs at three medical colleges, the NIV unit at Alappuzha for ZIKV testing, while the Rajiv Gandhi Centre for Biotechnology is already equipped for the same.
Difficult to detect
The district health administration and epidemiologists have pointed out that even though the current crop of cases have been reported only from the capital district, it is very difficult to detect ZIKV, unless one specifically looks for it. Given the high density and the omnipresence of Aedes Aegypti, the primary vector for ZIKV across the State, it is highly possible that the geographic spread of the infection is much larger than what has been revealed now.
The Health Department reported that while five samples had tested positive for ZIKV on Thursday, 16 samples had tested negative for the same. However, this might be no consolation as an RT-PCR test can detect ZIKV only during the viraemia phase, when the virus is active in the body.
About 80% of the ZIKV cases would have no symptoms and the remaining would have only mild symptoms which resolve itself within a three or four days. Hence the timing of the sample collection for testing is very crucial. If samples of patients who were symptomatic, tested negative, it could be just that the PCR test did not pick up the infection, not that they never had ZIKV.
Follow-up needed
This means that any pregnant woman amongst those who tested negative would also have to be followed up closely and mosquito-control measures would have to be carried out intensively across all pockets from where cases with fever and rashes were reported.
